I'm currently on my third Magna, a 2003 TJ @ 177,000 kms, but it is doing my head in regarding ilde control issues. About 3 months ago it began to intermittently (more often when it was cold) idle too high (1400 to 2000 rpm) or it began to hunt for its idle. Whilst I'm not a mechanic, I am an engineer so I thought I could think through the isses and solve it. So far I've:
* Cleaned Throttle body
* Cleaned and checked ICS
* Cleanded MAF sensor
* Run motor with, seperately, the MAF and Temp sensor disconnected and still no better.
I finally took it to local mechanics who checked diagnostics and first said ICS was out of calibration so they've reset, but still have same problem. Took it back and checked ICS and all OK but now they are saying possibly something to do with computer sending random signals to ICS. I'm no technician, but is this a real issue and if not is there someone who could give me other ideas about how to solve? Thanks in advance.

Welcome to the club.

I've got a very slightly rough idle I haven't been able to fix for months now. I've:
- cleaned the throttle body
- cleaned points in the distributor cap
- replaced leaking plug tube seals
- replaced rear spark plugs
- replaced ignition leads
- replaced distributor rotor
- checked for vacuum leaks
- cleaned and checked the EGR and PCV systems

It's driving me insane. Hope you get it sorted.

Thanks flyboy. I had a similar issue with my TJ a few years ago (at about 140,000 km) and I did similar to you. In the end I found that it was the distributor cap. There is a carbon contact in the top of the cap with a spring that forces it down onto the center of the rotor. The spring had failed meaning there was not enough force pushing carbon contact down, thus causing idle issues. This sorted out my issue and hope info helps troubleshoot yours.

I'm not sure if my issue is mechanical - I think it might be more electric or electronic. Mostly when cold, the ICS seems to be being sent a signal to adjust the air bypass, thus causing the high/fluctuating idle. The issue for me is why is it being sent a random signal. Hoping that someone may have some ideas!!

The ICS is driven by a stepper motor which is controlled by the ECU. To maintain a particular idle speed, the ECU adjusts the ICS valve and also jiggles the ignition advance (can be seen with a timing light). I think it unlikely that there is a random signal to the ICS unless there's a severe wiring problem, but people may interpret the actual signals as being random because of the way the ECU drives the stepper motor to try and control the air flow (and how rapidly it tries to do it).

Anything which alters how the airflow responds to ICS changes will conflict with the response the ECU's adjustment mapping is conditioned for, resulting in the ECU having very poor control. If things are far enough out of whack, the ECU might (don't know for sure) try and reset the ICS position, which could lead to hunting.

If the resistance of the ICS stepper motor windings has been checked and all four are within spec then the stepper should be okay.

Idling high with a working ICS suggests more air is being sucked through the MAF than the ICS valve can control - which might point to a sticky throttle blade or throttle cable.

Another scenario that I can think of which might also produce this behaviour is a combination of a vacuum leak and a dead oxygen sensor, resulting in an excess of both fuel and air at idle (when vacuum is strongest).

If simply resetting the ECU (by disconnecting and reconnecting the battery) changes the behaviour when it is most likely to occur, that might give some clues about where the problem could be.

Thanks for your comments WytWun. I agree that it is highly unlikely to be an ECU - there is no history of ECU problems with the magna and it seems to be "too complex" a solution - I feel that the solution is a lot simpler - possibly staring me in the face!!!

I appreciate the comments on the ECU algorithm and how it could end up hunting - need to use this when finding the solution.

I personally checked the ICS resistance and was fine.

I'd like to hear your thoughts on the MAF - I had considered and then discared that theory that it was a faulty MAF. Is there a diagnostic test for the MAF?

I've checked for vacuum leaks as well as I can, but found none. However I have noticed that when I remove a vacuum hose from the inlet housing, there is no real chnage in idle speed, possibly indicating that there already is no/not sufficient vacuum.

I considered the oxygen sensor some time ago, but not researched it. My (limited) understanding is that a faulty O2 sensor would affect fuel consumption, and at the momnet I use about 12.2 l/100km. This has been slowly increasing over the years as the engine becomes less efficient.

There is no appreciable change when I reset ECU by disconnecting batter, the only outcome being that I have to reset the time on the radio !!!!

Any thoughts would be appreciated.

You checked the ICS - but perhaps when it gets hot in the engine bay it starts to intermittently fail? - really sounds like an ICS failure.

Have you also checked the idle gap on the throttle butterfly - if it's not to tolerance the ICS might not be able to compensate.

I'd like to hear your thoughts on the MAF - I had considered and then discared that theory that it was a faulty MAF. Is there a diagnostic test for the MAF?

While replying earlier I did think about the MAF - while they occasionally cause trouble, it seems to me that faulty airflow readings would be much more likely to cause it to run poorly (either rich or lean, or all over the place) than to just lead to a high but apparently well behaved idle.


I considered the oxygen sensor some time ago, but not researched it. My (limited) understanding is that a faulty O2 sensor would affect fuel consumption, and at the momnet I use about 12.2 l/100km. This has been slowly increasing over the years as the engine becomes less efficient.
The oxygen sensors do deteriorate with time, however...


There is no appreciable change when I reset ECU by disconnecting batter, the only outcome being that I have to reset the time on the radio !!!!
Resetting the ECU not producing any significant change would tend to suggest that the oxygen sensor is not yet a major issue.

I think you can eliminate the MAF, since unplugging it did not fix the problem. With the MAF unplugged the ECU substitutes failsafe airflow measurements in place of the real thing, so the engine still runs (inefficiently, but without the issues you describe). You mentioned that removing a vac line made no difference, do you recall which one? Unplugging some of the lines should result in a drop in idle speed and a corresponding roughness. The other thing that might be worth considering is the coolant-temperature-controlled valve in the bottom of the throttle body. There's a wax pellet that increases or decreases idle airflow based on the temperature of the coolant flowing through the bottom of the TB, independently of the ISC. To be honest I don't know what the effect would be if this was damaged or if it would result in your symptoms, but if the fault varies in intensity at different engine temps and the ISC has been determined to be ok, there's not much else I can think of. Apparently the wax pellet can be damaged by the entry of throttle body cleaner into the intakes just before the throttle valve, they should be plugged if cleaning the TB on the car.

Thank you for your comments Ensoniq5. In response;

1. Your commenst on the disconnected MAF make sense. If the MAF was disconnected and the idle still hunted, must be something else sending improper signals.
2. I removed the vac line that connects to the rubber inlet housing that is a ribbed, flexible 90 degree elbow that pushes onto the TB. Not sure what this particular vac line does, but it is at about 9 o'clock when looking into the TB. When I hold my finger on it, there doesn't seem to be a huge suction (not as much as I expected anyway). Is there another vacuum test available?
3. Your wax pellet theory is new to me. I will check it out. I have been known to be quite liberal in using TB cleaner, and when it drained into the holes at the bottom of the TB, I just thought it would slosh around the ICS plunger and evaporate/get flushed out.

I will research the wax pellet idea and let you know. Any other thoughts?
Vito

Maybe a stuck egr vavle

The hose you describes sounds like the PCV (positive crankcase ventilation) intake pipe. Removing it will make no difference to the running of the engine, it basically lets fresh, filtered air into the top of the engine to replace fumes sucked out when intake manifold vacuum is high (or pressure is low, depending on how you look at it!). If disconnected, it will just let unfiltered air into the engine. There are a bunch of vac lines arrayed across the top of the TB and in the plenum chamber near the TB, the actual arrangement varies a bit between models I think but if yours is a TJ it will probably have three across the top (hoses are yellow, green and red) and a blue hose into the plenum just below them (there's also a black one that runs to the fuel evaporation cannister or something, from memory). I don't there is any problem with them, if any were leaking it would be more likely to result in low, lumpy idle or power loss rather than fast idle speed, but it's worth checking that they are all fitted well and not leaking.

I don't know if the wax pellet is the answer or even likely to be honest, I have zero experience with one that's damaged so I don't know if it would create the symptoms you describe. For this sort of thing I would always recommend having someone look at it who really knows Magnas and can run proper diagnostics, I don't know if there is anyone like that near you.

Just an idea out of the box I had the same problem in the end it was the alternator.

Thanks for posts.

Wombatkarl - tried that - but thanks anyway
Ensoniq5 - your memory is good, hoses are as you describe. I will check anyway.
Drunken2295 - altenator??? Really? how would that change idle? I did consider that it could be the battery as I know when you have a failing battery, the car will stall after startup etc. I would have to check it out.

I will mention one thing, and that is since I gave the TB another clean the other day, I don't seem to be getting the hunting issue anymore, either when hot or cold. The issue seems to be only in the morning when cold where it idles at about 1800rpm. When I get to the kids school (about 4 minutes away) and switch car off, when I restart the car the idel sits at around 1000rpm, and within another 5 minutes it seems normal, between 700 and 900rpm depending on load on motor - aircon/fan etc. Maybe it is a coldmotor issue??

On the issue of a Magna expert, is there anyone in metro area Perth??

Yer thought the same but when i had the engine change with mal he checked everything and tracked it back to the alternator once it was replaced had no problems.

The hose you describes sounds like the PCV (positive crankcase ventilation) intake pipe. Removing it will make no difference to the running of the engine, it basically lets fresh, filtered air into the top of the engine to replace fumes sucked out when intake manifold vacuum is high (or pressure is low, depending on how you look at it!). If disconnected, it will just let unfiltered air into the engine.

Are you sure about this? It actually sucks (venturi effect) crankcase fumes into the intake plumbing. Having it disconnected or leaking has a big effect on idle, as it is letting in unmetered air. At least, if you are going to run the engine with this hose off, cover the opening with tape or something. (The intake rubber hose is prone to splitting at that point too. )

Thanks Madmax - I had a look at the hose and it disappears somewhere under the inlet air plenum - not sure where it connects to.

Esoniq5 - Is the PCV valve the small balck one-way-valve that interst into the front rocker-cover on the right hand (drivers) side of the motor? If this is the one, the hose leads back and connects to the block between the V of the pistons.

Anyhow, definately when I remove the rubber hose I described connecting to the ribbed elbow on the intake plumbing, there was no noticable difference in engine idle. Also, when I took Esoniqu5's advice and removed some of the vacuum hoses that sit on the top of the TB, there was also no discernable difference. Does this point to a vacuum issue???

MadMax, when you mention unmetered air, you are referring to the fact that all air entering the TB must pass thru the MAF, thus being measured and accounted for? I could do some testing, but I get the feeling that it doesn't matter how much air enters the TB unmeasured it doesn't really make any difference to the idle on my Magna. Would this suggest some other underlying issue??

I had a big relentless idle issue in the KL AWD (check members ride thread about it)

It ended up being a slipped timing belt on the back bank. Belt and tensioner were replaced once discovered. Car is super smooth.

Are you sure about this? It actually sucks (venturi effect) crankcase fumes into the intake plumbing. Having it disconnected or leaking has a big effect on idle, as it is letting in unmetered air. At least, if you are going to run the engine with this hose off, cover the opening with tape or something. (The intake rubber hose is prone to splitting at that point too. )

True. I meant to say it would have little effect on idle speed as (I thought, but I could be wrong) the MAF didn't really come into play at idle. Theoretically, if the PCV valve is working correctly, minimal fumes should be sucked from the upper PCV hose through the TB since the PCV valve is one-way (Vito - yes, that's the PCV valve). Fumes should only ever be sucked into the intake manifold through the valve when manifold vacuum is high. In practice, most engines still fume when manifold vac is low (open throttle) especially if the rings are a bit worn, so some fumes and crap always flows the wrong way. Presumably this is part of the design otherwise there'd surely be another one-way valve at the other end of the PCV system to prevent TB gunking. I have heard of folks fitting inline filters to this hose to prevent (or at least decrease) TB fouling, I have no idea if this is a good idea or not. From what I've seen, so long as the PCV hoses and valve cover baffles are clear and breathing and the valve is in working order (rattles and only sucks, doesn't blow) and your rings are reasonably ok there's really not much gunk coming out this hose. I cleaned my TB over a year ago at the same time as replacing the PCV hoses and everything still looks clean and dry.

Vito - Removing some vac lines could have a minimal effect, but removing the blue one into the plenum should have a noticeable effect as it would dramatically lean the mixture. Some of the others only have vac at non-idle speeds. It doesn't sound like a vac issue anyway, I could be wrong but I can't think of a situation where leaking or non-existent vac could cause your symptoms. It definitely seems to be temperature related, if the engine temp sensor has been eliminated as a possible cause the only other thing I can think of is the wax pellet or (very unlikely) a damaged ECU.

Thanks Ensoniq5 - tried removing all of the vac lines but couldn't really tell too much difference. I also checked the erg as per a previous post and it seemed to working fine - as i understand it open at higher revs and I could visually see this happening.

I think that it does seem to be temperature related as it only seems to happen on the first drive of the day, however, even today after driveg for about 15 minutes the idle started to hunt again!!!!!! Not sure what else I can do.

Are you sure about this? It actually sucks (venturi effect) crankcase fumes into the intake plumbing. Having it disconnected or leaking has a big effect on idle, as it is letting in unmetered air. At least, if you are going to run the engine with this hose off, cover the opening with tape or something. (The intake rubber hose is prone to splitting at that point too. )

Max, I may be mistaken but I believe that the spring tension of the PCV valve is deliberately strong enough such that the vacuum generated in the intake manifold does not open the valve without any kind of positive pressure from the other side.
Hence why when unplugging the PCV valve while the engine is running you need to cover it with your finger to test if it works or not

Could it be a partly corroded/damaged socket/plug running to mad sensor or similar, meaning signal is being partially disrupted?

How a PCV system works:

Two hoses, front rocker cover to lower aluminium intake section, with PCV valve.
Second hose goes from rear rocker cover to the rubber intake tubing just before the throttle body. No PCV valve.

Idle: low air flow at TB intake tubing, no suction at rear hose.
High vacuum in inlet manifold, front pcv valve is open and sucking any fumes into the intake manifold lower section. (My TL one rattles at idle, and has strong suction.)

WOT:
High flow at intake TB tubing, strong venturi effect, crankcase fumes sucked into the intake tubing before the TB. (Hence the oil grot some people get in their TB.)
Low vacuum in lower intake tract, hence low or no suction past PCV valve on the front hose.

Between the two hoses, there will always be some lower pressure in the crankcase, and any blowby gases are sucked into the intake, either at the lower manifold or at the TB.

Thanks for all the posts. I thought I had it solved today when I took apart the wax pellet Idle valve. It was pretty full of gunk and sticky any completely cleaned it but if doesn't seem to make any difference. Still seems to be temperature related though. I'm out of ideas!!!!

I'm out of ideas!!!!

Here's 2 ideas:
Error codes.
TPS.

Thanks madmax. The only error codes it comes up with are when I disconnect the various sensors (eg maf or temp sensor) for diagnostic purposes.

The tps is a new idea. Is there a diagnostic test for the tips?can I disconnect and run car without???

Is there a diagnostic test for the tips?can I disconnect and run car without???

TPS = Throttle Position Sensor. Located on the throttle body at the other end to the ISC.

Just a multimeter will do. You need to look at the manual to see pinouts.

One set is a switch, should be closed when the car is idling so the ECU knows to activate the stepper motor (ISC) to maintain a steady idle. When it opens the ISC is not active. There is also a rheostat - the other two contacts - which should give you a linear increase in resistance as you slowly open the throttle. (Test can be done with the ignition on but the engine off).
If it is open circuit and can't be adjusted (undo the 3 screws, turn clockwise or anticlockwise - switch should be closed with no throttle input, but go open circuit as soon as you move the throttle pedal) or the variable resistor in it is not linear, it needs to be replaced.

I wouldn't use the car with the TPS disconnected, no idea what would happen, but the variable resistor part tells the ECU how much throttle you have open and tells the transmission how to shift smoothly. Probably get some nasty hash shifts if you do disconnect it, but I'm guessing.

Thanks madmax. Will try this out. Also found some tests on the Internet. I did notice one very strange thing today-i hardly use any oil between services, or at most maybe 0.2 litres. However, I have been noticing that since my idle issue ive been chewing through the oil, maybe 2 litres a year. Not sure if these are related but don't seem to be blowing any smoke out the exhaust. Could the oil be gunking up a sensor or something?

Ok. Trying to be a bit more scientific. I waited for the car to be idling at the correct rpm (700rpm) and then I disconnected the ics (as the ics is a stepper motor, once disconnect it should stay where it is). The result is that the car drives well when warm, it just needs extra throttle when cold. However my thoughts are that it must be a sensor that sends a signal to the ics because there is no idle issue when disconnected. That then rules out other things like vacuum leak, egr, etc. The question is now, what other sensors send signals to the ics? Maf, tps, temperature???? Anything else?

Idle stepper motor is subject to only one input, that is from the ECU.
As it is a stepper motor, it needs precisely timed pulses to make it move the right amount in the right direction. Only the ECU can do that.
The ECU gets signals about coolant temperature, crank and cam position, air flow, throttle position, and probably a lot of others I can't think of at the moment.

In my opinion, disconnecting things on a running EFI engine as a fault finding technique is not recommended. What do others think?

I suspect you have a vac leak, particularly since removing even the blue vac line to the plenum had little effect, and/or a blocked PCV system. A blocked PCV system will result in excess oil usage and a build up of gunk as blow-by gasses mix with engine oil and can also lead to idle hunting. The simple way to check the valve is, with the engine off, remove the PCV valve (at driver's side of front valve cover) by disconnecting the hose and plucking it from the grommet in the valve cover. The valve should rattle when shaken and you should not be able to blow air (with your mouth) backwards through the valve (ie. with the hose fitting in your mouth). Additionally, the valve should begin to close as air is blown or drawn through the other way, though I don't know if you can test this with your mouth. In effect, the valve is a one-way valve preventing a backfire from passing into the valve cover and potentially starting a fire, and it also regulates the amount of ventilation by sucking closed against spring pressure when there is a high manifold vacuum relative to atmospheric (ie. decelerating or at idle). If you suspect it's dodgy, Repco have them for about $15 (OEM is something like $90!). You can also test it with the engine running by reattaching it to the vac line but leaving it out of the grommet, running the engine and placing your finger over the valve opening. You should feel suction and the valve should click open and shut as you remove and replace your finger.

Secondly, the PCV system could be blocked in any of the three hoses and two valve cover baffles. The three hoses are the one in the air intake just upstream of the throttle body which leads to the rear valve cover, a second pipe running from the rear cover to the front cover (above the distributor), and the third pipe running through the PCV valve to the intake manifold. Additionally, to limit the amount of oil passing through the system and to reduce the likelihood of fires if a backfire occurs, each valve cover includes a built-in baffle that allows the passage of air but inhibits liquids. The simple way to check if they are clear is, with the valve plucked out, block the grommet with your finger. Pluck the PCV intake hose (near the throttle body) from the air duct and blow into it with your mouth (make sure the oil filler cap is on). With the grommet blocked you shouldn't be able to blow much air through the engine, and with the grommet clear you should be able to. There will be some resistance through the baffles but if you can't blow air you'll need to determine where the blockage is. New PCV hoses are available from dealers and the baffles can be cleaned out by removing the valve covers from your engine and soaking in degreaser or kero. This is a good time to replace the valve seals, there's a few tricks to that but there's plenty of threads on the subject, some of which are even accurate!

The manual's diagnostics charts also suggest an air leak as a likely cause of idle hunting. This can be in any number of places, including if the EGR valve isn't seating properly or if a vac line is split. You should have three hoses running to the top of your throttle body: Yellow (to terminal A), Red (to terminal P) and Green (to terminal E). There should also be a blue hose to the plenum chamber just near the throttle body (under the other hoses) and there should be a black hose running with the others and over the top of the air duct and down to the fuel canister. The yellow hose runs to the EGR solenoid (the white solenoid valve to the passenger side of the front valve cover. From this valve, the green hose returns to the E terminal via a T-junction, with the other branch running to the EGR valve diaphragm. The red hose runs to the purge control solenoid (the driver's side solenoid valve) with the black return hose heading for the fuel canister. Finally, on the back of the plenum chamber, a large diameter vac line runs to the brake booster. Make sure all lines are tightly fitted and none are split, if any are loose or suspect they might need to be replaced.

As I understand it (and I could be wrong), terminals P and E develop vacuum when the throttle is open from the venturi effect of air passing through the throttle restriction. If the EGR solenoid is closed (controlled by the ECU) this vacuum is communicated to the EGR valve diaphragm and the EGR valve opens. If the solenoid is open the vacuum is defeated by air flowing from terminal A which is before the venturi and effectively at atmospheric pressure, so the EGR valve closes. The venturi vacuum developed in terminal P is used to draw fumes from the fuel canister, controlled by the ECU via the purge control solenoid. So, at open throttle, you should feel vacuum at terminals E and P and not at A, and at idle there will be little vacuum available in any of them. The blue hose (terminal M though I don't know if it's labelled) communicates manifold vacuum, which peaks when the engine is running and the throttle is closed (idle and decelerating), to the fuel regulator, and the big hose on the back does the same for the brake booster. Removing either when idling should have an immediate, noticeable effect as the air/fuel ratio leans out; if not there could be a leak in one of these systems (

There's too much involved in checking all solenoids and valves to go into details here, if you suspect the fault could be in this area I would recommend searching for the PDF manual (a couple of threads discuss where to download it, I think some URLs have broken but some are still active. Or Google it as I did) which runs through the testing procedure for each component. Air leaks can occur elsewhere including a cactus manifold gasket but I would think that was unlikely if it hasn't been disturbed. The EGR is another strong possibility particularly since the ECU opens or closes the solenoid depending on engine temperature, which seems to be a factor. If you suspect the EGR you can temporarily replace the gasket at the top of the gas riser tube at the driver's side of the rear of the plenum with a blank made from an aluminium can (purely as a diagnostic, don't leave it this way). If the problem remains the EGR is not the culprit.

Idle stepper motor is subject to only one input, that is from the ECU.
As it is a stepper motor, it needs precisely timed pulses to make it move the right amount in the right direction. Only the ECU can do that.
The ECU gets signals about coolant temperature, crank and cam position, air flow, throttle position, and probably a lot of others I can't think of at the moment.

In my opinion, disconnecting things on a running EFI engine as a fault finding technique is not recommended. What do others think?

I agree. I wouldn't recommend disconnecting things while the engine is running. Starting with the disconnected, maybe, as a diagnostic.

Thanks Ensoniq5 et al. I've had a bit of time and have covered off the following;
* Checked the PCV Valve - this was u/s and I've replaced
* Blown air through the motor through the respective vacuum hoses and still no difference. I did notice that there was some gunk in the hose that connectes the front and rear rocker cover.
* Checked the EGR riser and seems clear, but still haven't tried blanking off just yet.
* Noted that some of the larger vacuum lines (8mm and 10mm) are quite stiff. The one to the PCV split at the end when I removed it. I'm going to replace these when I get the chance.

The thing that still confuses me is the disappearance of about 2 litres of oil in 3 months. I've checked exhaust and that is ok for a 177k car, and my fuel economy is still relatively good. I was wondering if this oil has hardened and collected somewhere in the motor causing the issue? I change my oil every year after about 13,000 km, and use a relatively good oil - Shell or Castrol. Could this be the case, and if not then where has the oil gone???

Vito

I think Castrol is a bit of an overrated oil.
Use Shell or Mobil instead.

Your oil is likely disappearing from your valve stem seals. Try this with the engine at operating temp:
1. Let the car idle for 5-10 mins
2. Floor the accelerator for a second
If smoke comes out of your exhaust then it signifies valve stem seals.

Thanks Spetz - I did as you recommend and yes, some smoke came out - not sure if it could burn through 2 litres in 3 months, but is at least part of the problem.

However still no joy of high and hunting idle. Changed all the larger Vac hoses ( to PCV, front to rear rocker cover, top of rocker cover to air intake) - still no change. I put in a new air filter since the last one's seal was not secure - still no change. Blanked off the EGR riser with piece of coke can - still no change.

Took a quick look at the ECU under the dash (I looked at it from the passanger footwell) to see if there was any water damage. It seemed to be wrapped in plastic and could see no evidence. However this did make me think, I recall that I fitted a bluetooth device that involved me taking out the centre instrument cluster at about the same time as problems started (No too sure of the timing though - generally about that time). Could I have inadvertantly knocked something near the ECU - I see that the ECU sits well back from where I was working - I basically installed the bluetooth under the ashtray. Thoughts?

Vito

My car also puffed a bit of smoke after extended idle and was using 1L per 2,000km.
I've recently replaced my valve seals and it no longer smokes, however have not driven enough to gauge if there is any oil consumption

Ok. Had some time now to do some analysis. I am dredging the bottom of the barrel of ideas, but I changed the battery with one closer to the spec and the idle issue is noticeably better - i have not had an issue with idle hunting since then. However things are not perfect. The car on most morings will cold start fine, idle up to 1600rpm and witin seconds come down to 1100 rpm, which is as i would expect. However, if i just let the car sit there and idle, it will stay at 1100 rpm rather than slowly come down as I would of thought as the coolant warms up and the Fast Idle Air valve closes. But..... if I start from cold and then after a few seconds , put in gear and drive off, it comes down to 800rpm idle and stays there when i put in neutral. However...... sometimes if i drive off and put in neutral sometimes it goes up to 2000 rpm after a few minutes and stays there, but................... if i switch the motor off and restart, it comes back to 800rpm. Not sure what is happening here if anyone has any clues. Once Ive driven to work it never seems to play up with idle speed again during the day, even after leaving my car in the work garage all day. For me definately seems temperature related.

Also, I got an idea from the forum that it may be the coil, so I took the dizzy cover off, removed rotor and backing plate, and sprayed liberally with contact cleaner. I did notice some oil at the bottom of the dizzy cover and some oil on the motor directly underneath near the grear adjustment cable entry into the gearbox. I've probably got a leaking oil ring on the dizzy however I don't think it is fatal at the moment. My question is could it be the coil giving me grief in the idle? My thoughts are that a malfunctioning coil would malfunction all of the time, not just when cold. Once over the cold idle issue the car runs quite well - idle is a little rough, but has done 170,000 kms. I have noticed on a few occassions (two or three times a week), where under acceleration the car would jerk forward quiet forcefully. At the time i thought it might be the gearbox, but on reflection, could be the coil killing the engine with no spark and then starting again?? Thoughts??

Thanks

I changed the battery with one closer to the spec and the idle issue is noticeably better

Did you allow the car to idle for 10 minutes or so after changing the battery so the idle speed controller could reset? if not disconnect the battery and try again, the improvement with the other battery might relate to a partial reset.

Thanks bb61266. Yes I let it idle for about 20 min. Also, when i am at the lights, i let it idle and put in neutral. I was reading that in some cases the computer can take some time to relearn stuff (Comments on the Forum like "took a month or so before idle settled down"). Also, as i understand it, when throttle is closed, a switch in the TPS allows the Idle Control motor to work - I think this means that the Idle control motor really only does work when throttle closed - it should not be operating when throttle is even slightly open. This makes sense since when the throttle is open there is no need for minor changes in idle as there is plenty of air going through motor to accommodate things like extra load from air conditioning. Reflecting on my huntig idle issue, i'm sure that took place when i was driving the car ie foot on accelerator, possibly meaning that Idle control motor was operating even when TPS should have switched it off?? Does this make sense?? and does this mean I have a TPS issue??? Any thoughts would be appreciated.

Thanks to all that have provided a post and a comment on my idle issue over the past few months. Just to let you know that a few weeks ago i bit the bullet and changed out the Idle Control Motor, contrary to the advice that the local (franchise) mechanic who said that there was nothing wrong with it and wanted to send my computer away for analysis. Anyways, the long and the short of it was that teh problem was the ICM - for some reasone its resistance read fine across the terminals but it would cause the idle to be too high and hunt when it was cold. Anyway, bought a local unit (new but not origional) for $120 bucks and now the car runs fantastic - well for a 10year old car anyway. I could probably have got a cheaper one but the local guy had it in stock and was just up the road.

In any case, thanks for all your comments - I ceratinly learnt alot about engine control systems!!!! And also, just because the local mechanic guy says it is ok, if the facts present otherwise, always check it out for yourself.

Appreciate the follow up, always good for a thread to have some sort of conclusion. I guess it's a lesson that sometimes the 'basic' test of a component is insufficient to diagnose a problem, and never trust a mechanic who doesn't know Magnas really, really well. I don't know anything about aftermarket ISCs re longevity/accuracy etc., if it's working properly then good result!

Thanks Ensoniq5 for all your comments. Thought bringing some closure would be good!!!!! I too am reluctant on aftermarket parts, but it was a low-cost diagnostic option. If it fails I can go pick up a gunuine, or hit the wreckers. Cheers