hey guys i need some help / advice on what's wrong with my car.
i have just bought a second hand 03 and drove it all the way from brissy up to mackay a month ago no problem but now its stalling out when i pull up at the lights while driving around town. its an auto 3.5 sedan and it just keeps having the revs drop so low that it stalls out but starts again the second i turn it over. i'm just guessing here but from the little i do know of cars it's a fuel filter/pump problem right?
is there a "cheap dummies guide" on how to fix this myself or should i just take it to a mechanic along with my firstborn? i hope it's just a fuel thing cos it might be a relatively easy fix from what i can surmise by reading some other posts here but if i'm completely wrong can someone point me in the right direction? cheers guys and thanks for the help in advance

I doubt it's a fuel pump/fuel filter issue.

Demand on the fuel system is at its lowest at idle, fuel starvation from a blocked pump would be more likely to manifest as surging or coughing at high RPM/high throttle when the fuel system can't keep up with demand.

There's a guide somewhere written by the resident Magna guru on how to disassemble and clean the throttle body, and this might be a good place to start. Search the forums or Google for it.

I assume it's not on LPG?

good luck with that problem mate!! could only try to guess, better leave it to the experts.

Does it idle well when the engine is started from cold, then the speed fades away as the engine warms up?

Idle speed is controlled by the ISC (idle speed control) which is an electrical motor on the side of the throttle body.

Either it is not plugged in (unlikely) or it has died (more likely). Get one from the wrecker. Put it in, then idle the motor for a while to get the ISC and ECU working together properly.

I just love the way you instantly jumped to fuel pump as the problem. No it isn't that!

hey guys well i'll try to give more info maybe we can narrow it down. i may own a couple of magnas but that's only because it takes a very big stick to kill them lol i've never been a real gear head

no it doesn't run LPG. it shudders when it first starts in the morning but most of my problem seems to be when i brake for an intersection even though i "feather" the brakes it feels like the car is just not bringing the revs into line.

it does it more often of late and i can't say if it's more prevalent when the car is warmed up as i don't drive it every single day.

is it at all possible that the gearbox needs a good service? i think MadMax is on the money with the ISC but i just remember how much hell my ford gave me with the torque converter and rough idling

will have to take it for a run today and see if it runs better cold or not. maybe out to the wreckers to search for a ISC or 6

i assume by speed fading away you mean the general idle speed dropping after it has warmed up Max? will check it today and let you know mate and thanks for the help guys

My guess is that it is an air leak somewhere. Probably a hose fallen off, or split. This allows a certain amount of air to leak in. At idle, the air demand of the engine is least and therefore the air leak will lean out the mixture the most. As you rev the engine, the leakage air remains the same (or even drops off a bit), but the airflow into the engine increases, so the leaning effect of the leakage is a lot less. Look for an air leak on hoses after the throttle body.

Was any work done to the car prior to the stalling issue? Was anything removed and reinstalled to do the job
It could be something simple like improperly secured intake piping or loose/cracked vac line; unplugged/stuffed ISC motor.
Check electrical connectors and air hoses/pipings in the engine for loose fittings.

Yes, check for air leaks, both on the big air inlet between the air filter box and the throttle body, and smaller hoses.
Check the big hose for tight clamps, and see if the resonators aren't split.

Step one, I would be cleaning the TB and making sure the hole for the idle screw isn't blocked.

Mike

My guess is that it is an air leak somewhere. Probably a hose fallen off, or split. This allows a certain amount of air to leak in. At idle, the air demand of the engine is least and therefore the air leak will lean out the mixture the most. As you rev the engine, the leakage air remains the same (or even drops off a bit), but the airflow into the engine increases, so the leaning effect of the leakage is a lot less. Look for an air leak on hoses after the throttle body.


Have to agree...also MadMax in relation to the ICM. My old TS wagon was doing EXACTLY as you describe your car as doing. My local mechanic installed a brand new idle control motor (a genuine Mits one) and the problem was gone. Note...it takes a while for the ECU and the idle control motor to "talk" to each other to normalise the idle. Don't worry too much if, after changing the ICM, the idle is a little iffy. After a couple of hours of driving the ECU should adjust and all should be well.

Don't worry too much if, after changing the ICM, the idle is a little iffy. After a couple of hours of driving the ECU should adjust and all should be well.

Sorry to argue with you, but the ISC is only active when the throttle is closed, ie the car needs to be at idle to get it right.
You may need to keep the rpm up with your right foot to stop it from stalling, but after a while it comes good.

Learnt this the hard way - drive, take your foot off the go pedal and it stalls. Not fun loosing power steering as you come into your driveway and you suddenly find the steering goes heavy and you are about to take out your letterbox!
Whenever I have had the battery disconnected I make sure the idle gets right before I drive anywhere.

I've found the Lancers do it the other way, reconnect the battery, start, and the idle goes really high, above 2,000 rpm, and then the ECU slowly adjusts the ISC back down to normal. It can still be unsteady for a while though. ECUs are slow learners apparently.

Sorry to argue with you, but the ISC is only active when the throttle is closed, ie the car needs to be at idle to get it right.
You may need to keep the rpm up with your right foot to stop it from stalling, but after a while it comes good.

Learnt this the hard way - drive, take your foot off the go pedal and it stalls. Not fun loosing power steering as you come into your driveway and you suddenly find the steering goes heavy and you are about to take out your letterbox!
Whenever I have had the battery disconnected I make sure the idle gets right before I drive anywhere.

I've found the Lancers do it the other way, reconnect the battery, start, and the idle goes really high, above 2,000 rpm, and then the ECU slowly adjusts the ISC back down to normal. It can still be unsteady for a while though. ECUs are slow learners apparently.

Don't worry...and don't be sorry. I am willing to learn from others. I was just quoting what the mechanic told me when he changed the ICM on my old 3L TS wagon. It seemed to take a day or two to settle down and it drove me nuts waiting but eventually it settled.

Sorry Max not time for me to argue with you....again

If the ISC is not functioning correctly the car can stall upon coming to stand still. When you are slowing down to a stop the ISC will slightly flare the throttle before returning to idle, if it is not doing this then you get the stall as the transmission load on the engine is too great for it to continue an idle.

Have had customers with this many a time. Seen it many a time and had it on my own cars over the years.

OP, when you are at idle and you put on the air con, do the engine revs lift at all, and also do the engine revs lift immediately before they settle. May be the ISC port is gunked up from not being cleaned, may be the ISC is no longer working

Hi there. I have a 2004 LPG LS. (Auto). For a while now the idle speed has been dropping off to the point of almost stalling.

I see in one reply that this points to the ISC motor, that is, if it idles high from a cold start, and then drops off as the engine warms. Is it worth testing the ISC, and if so, how do I go about it?

It's confused me a bit because the idle speed picks up when the A/C kicks in (though not as high as it should be), so I've been assuming it was not the ISC. I've also read elsewhere it can be due to a dodgy battery (3+ years old at this stage). Put me straight fellahs please! :kb: