I'm starting a new thread to avoid polluting Rumpfy's canister thread any further.

My TP's rough running at hot idle continues and I now think it could be because the carby float level is too high or the needle not seating properly. The TP carby float level is not adjustable as in the TM but some judicious bending of the float bracket can achieve a similar effect. I was about to take the carby off and have another try at that until Rumpfy posted the following:


Coldy,
To check your theory, it would be possible to get the fuel control relay out from behind the panel, and when you stop as you say, then when the engine starts to miss, unplug the fuel pump and see if the miss disappears.........

Due to interruptions, I didn't get to the carby yesterday. That may be a good thing as I will give your suggestion a try first.

This morning, I took the fuel pump control unit out. There's not a lot of slack in its wiring, so I cut the wire from terminal 6 a few cms from the plug and soldered in a short loop of wire to a slide switch. I mounted the switch on the plastic panel in the footwell below the glove box. The fuel pump control unit was then re-fitted in its original position.

Now I can easily switch the fuel pump off anytime. I will try it tomorrow if the rough idle problem occurs on my weekly trip to Tamworth.

Incidentally I thought I nailed the cause of the rough idle problem last week but it was a false hope. I considered that the ignition module in the distributor might be the cause and decided to check whether it could be replaced without removing the distributor and upsetting the ignition timing. In the meantime, I would check its wiring and connections for corrosion.

You can, in fact, remove and replace the module with the distributor in place. Just be careful not to drop the screws. The module seats against the alloy extended base plate of the distributor which acts as a heat sink. Short lugs protruding from the back of the module locate into holes in the base plate and thus help keep it in position. Two mounting screws pass though a metal cover plate and then go right through the mounting holes at each end of the module and screw into the distributor base plate.

The wiring and connections of mine were fine but I was shocked to find that the mounting screws were very loose. The screws need to be tight to ensure the heat generated by the module is conducted away by the distributor baseplate and the module's cover. Of course I tightened the screws and was hopeful this would solve my misfiring at hot idle. Unfortunately it didn't but it did cure the erratic flickering of the tacho needle.



ps saw a $800 TS verada today.

I've been negotiating on a TP elite but the seller didn't forward photos as promised and has now sold it to someone else. I have 3 months before the rego on mine expires so don't need to rush. If I fix mine, I will just renew the rego but I'm keeping an eye out in case anything better becomes available locally at the right price.

If you let it idle for a few minutes when hot and running rough then stop the motor and pull the sparkplugs out what colour do they have?
When you open the throttle ever so slightly to take it from the ilde circuit and jets and to venturi does the engine run smooth straight away? Cheers Vee

If you let it idle for a few minutes when hot and running rough then stop the motor and pull the sparkplugs out what colour do they have?

I didn't take the plugs out today but have done so on several previous occasions and wasn't able to make a clear diagnosis They were generally brown colour with Nos. 2 and 4 slightly darker. If you are familar with the spark plug condition images on the inside back cover of the Haynes workshop manual, I'd have to say my plugs are closer to "normal" than any of the other conditions illustrated. I replace the plugs much more frequently than really necessary, so they would never get a chance to exhibit any of the more extreme signs of wear or damage. They certainly weren't oiled up or choked with carbon either.


When you open the throttle ever so slightly to take it from the ilde circuit and jets and to venturi does the engine run smooth straight away? Cheers Vee

No. Even if you take it up to 3,000 revs or so, and no matter whether gradually raising the revs or blipping the throttle a few times, nothing will clear it with no load applied. On the other hand, a quick blast down the road for a km or two with an extended burst at full throttle will usually clear it but the rough running may or may not return when left idling again for a minute or two. The frustrating part is that it is so unpredictable.

The only thing I can say with certainty is that it is always ok when started from cold. The hotter the engine is, the more likely it is that the problem will occur. The degree of roughness also seems to increase with engine temperature.

Now to today's experiment: When I restarted the car after arriving in Tamworth and stopping for fuel it ran rough, so I pulled into the carpark nearby and turned off my fuel pump switch. It made no difference at all. The rough running continued for a few minutes until all the fuel in the carby bowl was used up and the engine stopped. Actually I was surprised how long it ran and was beginning to wonder whether I'd wired the switch correctly. When it did stop, it did so suddenly with no coughing and spluttering. Until then it continued idling roughly with a rythmic sort of misfire. I tried revving it a little and blipping the throttle but that didn't help either.

I think that disproves my theory that it was running rich at hot idle due to too high a float level or the float needle not seating properly. If that were the case, it should have smoothed out as the fuel level in the bowl decreased. I don't think it could be the opposite either (i.e. running lean) because it didn't get worse either.

I suppose that puts suspicion back on the electrics. I will order a new ignition module. If that doesn't fix it, the distributor itself is about the only thing left.

Coldy,
Have to get serious now!!!
1. Is the problem due to electrics or is it vacuum?
2. Have you run a vacuum gauge on it?
3. Is the Bowl Vent Valve OK?

The tacho is driven from the coil primary circuit and if there is a problem in the electrics, you might see a slight fluctuation in the tacho needle as the motor misses. If the beast misses and the tacho stays stable, then maybe you can rule out the module. I have replaced an ignition module in the TP. The original was presumably Bosch. The faulty module in my TP was an aftermarket type. It was intermittent and would play up when hot. When playing up, the tacho needle would waver slightly. If you can get some one who has an oscilloscope that would allow you to check the module. I have an old Tektronix CRO and it lets you see what is going on. The coil voltage waveform tells you everything you need to know about the performance of the module.
I still have the orphan vacuum gauge here waiting for its new address. It would be good enough to check manifold conditions at idle. Can't give you the CRO but.

rumpfy

Coldy,
Have to get serious now!!!
1. Is the problem due to electrics or is it vacuum?
2. Have you run a vacuum gauge on it?
3. Is the Bowl Vent Valve OK?

I don't think it can be vacuum. I've tried closing off and opening various vacuum lines and that makes no difference to the rough running. There is nothing currently connected to the thermal valve so if the problem was vacuum related, there is no reason why it should be temperature-dependant.

There is also no reason why the problem would be temperature-dependant if the BVV were the problem. I am fairly sure it is ok.


The tacho is driven from the coil primary circuit and if there is a problem in the electrics, you might see a slight fluctuation in the tacho needle as the motor misses. If the beast misses and the tacho stays stable, then maybe you can rule out the module. I have replaced an ignition module in the TP. The original was presumably Bosch. The faulty module in my TP was an aftermarket type. It was intermittent and would play up when hot. When playing up, the tacho needle would waver slightly.

I think the module in mine is also aftermarket. It looks fairly new but may have been damaged by overheating due to the mounting screws not being properly tightened.

It is interesting that you mention tacho fluctuation. As I said in my first post in this thread, tightening the ignition module mounting screws eliminated the previous erratic flickering of the tacho. However there has for some time been a rythmic fluctuation of the tacho needle and that did not change. In fact I took particular note of it today, trying (unsuccessfully) to understand the reason for it.

When driving at any normal cruising speed, the tacho fluctuates regularly up and down within a range of perhaps 150 to 200 rpm. It is very similar to the way old cable driven tachos used to fluctuate due to cable whip when there was a significant bend in the cable.

When driving uphill or under load, the amount of tacho fluctuation increases slightly but if the hill is sufficiently steep for the transmission to drop down to 3rd, the tacho needle then becomes as steady as a rock after the downchange and increase in revs. I can't think of a reason why that should happen. The speedo, by the way, is rock steady at any cruising speed.

Anyway, I can get an aftermarket ignition module for $44 delivered or a genuine Bosch one for $75. For that small amount, I might as well do so as it wouldn't hurt to carry a spare.

Thanks for your suggestions.

Edit: Just ordered one this morning and it was posted within minutes, so should be here on Monday.

Coldy,
In the days when I drove a company TM magna, one of the guys had a TN Magna. This was the first model after the auto trans problem became obvious. This particular car showed a similar fluctuation you observe. I noted this characteristic and was told the problem in the car was subject to investigation by MITS. From memory the problem was related to the front clutch engaging and disengaging cyclicly, and was related to the transmission fluid. The Mits transmissions have their own composition fluid; Is your transmission behaving badly?. Does it need an oil change?. Generally, the front clutch is controlled by the speed loss in the torque converter. Under 'heavy' load, the speed loss is high. As the vehicle comes up to light steady speed loads, the speed loss in the TQ reduces and this signals the front clutch control to activate. You can induce the front clutch to activate by taking your foot off the accelerator. Just what the algorithm is to release the front clutch I cant say.

On the missing, is it possible you have a faulty spark plug.? A resistance check of the ignition leads is always interesting to do. Should be less than about 30 K ohms and if you jiggle the cable a bit, the reading should be steady.
regards,
rumpfy

They were generally brown colour with Nos. 2 and 4 slightly darker. If you are familar with the spark plug condition images on the inside back cover of the Haynes workshop manual, I'd have to say my plugs are closer to "normal" than any of the other conditions illustrated.
if it was rich they would be black and sooty after a few minutes at idle.
If you had a vacuum leak it would be a lean running motor at idle and you would get white plugs after a while but it would also usually happen across the operating range.
Under hot conditions it could be the coil or leads breaking down! I cannot remember if you had tried these.
What is the compression for each cylinder?
Last year i rebuilt my TP it had a slight uneven idle all of its life and lower compression on No2 cylinder........... Nobody could fix the idle.......
Only done 150k but as i replaced the cam chain and removed the balance shafts i elected to do the rest of the bottom end!! On removing No2 piston it had a broken no2 compression ring.......Engine was stock and not had anything done to it since new i new the car and owner from brand new.
Possibly happened from assembly at plant.......Idle now perfect and compression on all 4 the same so obviously the reason for the uneven idle all of its life until rebuild. Vee

This was the first model after the auto trans problem became obvious. This particular car showed a similar fluctuation you observe.
Yup had a TN wagon company car one of the first on the road in NSW a couple of months and 20k the same problem showed up as you mentioned.
Mechanics thought it was a jet problem so stripped the carby and rebuilt it.....No change then they found out about the Auto's!! Serviced it and flushed and new Mitsi fluid corrected the fluctuation. I noticed it first under load up hill throttle position constant and you got a slight surge and tacho did the same......Kickdown and under power it was not present. Vee

Coldamus have you checked the Hot Idle Compensator thats under the bottom half of the air filter body?? Vee

Thanks for all the suggestions, guys. I'll try to answer all questions but not necessarily in the order asked.

I forget which thread I mentioned it in but yes, I checked and fixed the Hot Idle Compensator. It did make a significant improvement.

Can't be plugs or leads. I've changed plugs a couple of times. I bought new Magnecor leads for both the wagon and sedan not long back (I know the Magnecor guys and got trade price). They are upmarket race leads with a lifetime guarantee. Nevertheless, they were among the first things I checked. The resistance is well in spec but I also swapped leads between wagon and sedan. The wagon runs fine on either set. I also swapped distributor caps.

The compression readings before I replaced the faulty head gasket were 145psi for No 2 and 155psi for 1, 3 and 4. I've since read that the throttle should be held wide open while doing the compression test so the engine can suck in plenty of air. I didn't do that. I no longer have access to a compression tester. My neighbor brought his over but has since moved elsewhere. Still, I don't think that's the problem because it always runs well when cold and sometimes when hot too. The problem is too intermittent for it to be that.

The transmission has no other problems that I'm aware of. When I bought the car, I flushed and replaced the transmission oil and fitted a new filter kit. I used genuine Mitsubishi parts and transmission oil from Parramatta Mitsubishi. I remember being dubious about the variety of Mitsubishi oil they gave me as the label didn't agree with what is specified in the manual. However they assured me it was the right one.

It is due for another change now and I tried to buy some transmission oil the week before last. That was a saga in itself. The Mitsubishi dealer is also the Holden dealer. I went to the address listed for Mitsubishi spare parts but it was only a sales office. They gave me another address for spare parts but no-one could describe how to get there, so I drove around at random until I found Holden spare parts. Mitsubishi is not even mentioned on the outside signage although the logo is displayed inside.

I asked for Mitsubishi Magna ELC-4-SP Automatic Transmission Fluid, as specified in both the owners' manual and the service manual. They couldn't find anything like that listed but it wouldn't have mattered because they do not stock or sell any variety of Mitsubishi transmission oil. They tried to sell me some generic stuff - can't remember the brand - maybe Caltex - and weren't impressed when I wouldn't accept it. I wasn't about to put my faith in a random guess by a sales receptionist who clearly knew zero about the subject. The nearest Mitsubishi dealers otherwise are in Gunnedah and Muswellbrook so I will have to try those but will ring first to save a wasted trip. Sorry, I got off track a bit here but am steamed up about the situation. Glad I'm not having a new Mitsubishi serviced there.

I think you may be right about the relationship between the transmission clutch and the tacho fluctuation but am not certain. I don't feel any surges corresponding to the tacho fluctuation and the speedo needle does not rise and fall. It is quite steady. On the other hand, I do feel a vibration sometimes when going uphill under load. I can't quite pin that down either so it may just be the road surface. It feels like corrugations in the bitumen although none are visible.

Anyway, we shall soon see whether the ignition module is the culprit. Once that's eliminated, I'll decide what to try next.

You can use a couple of other brand transmission fluids in the Magna.
The Gregories Manuals state BP Autran MM and Mitsi ELC-4
I have used Castrol TQ-M and had no trouble in the last 10 years its made specially for Mitsubishi now TQM-ST
Product Description
Castrol TQM-ST is a semi-synthetic automatic transmission fluid specially formulated to suit the friction requirements of Mitsubishi, Hyundai and Proton automatic transmissions, especially those fitted with damper clutches and calling for either the SP II or SP 2M specification.
http://www.castrol.com/liveassets/bp_internet/castrol/castrol_australia/STAGING/local_assets/downloads/a/AU_Castrol_TQM_ST.pdf

Nulon also make one for Mitsi that i have used on other magna. Vee

Vee,

Thanks for that info. Repco in Tamworth stock Castrol transmission oils so I will be able to buy some there if I have no joy at the other Mitsubishi dealers.

regards,
Coldamus

The new ignition module arrived today and I have just finished fitting it. The car still runs, so that's a good sign. :)

I see now how easy it would be to accidentally leave the mounting screws loose. If the module cover is not seated down perfectly, you think it is all tight when there's really another few millimetres to go. That would result in a poor earth contact as well as poor heat sinking. Let's just say that mine is definitely tight now. When tightened fully, the mounting screws protrude though the bottom of the distributor base plate by 1 to 2 mm.

Its first real test will be on my trip to Tamworth next Wednesday, so I will report the result then.

The new ignition module made no difference at all. I still think the problem is electrical because no amount of blipping the throttle or revving the engine will clear the misfire. The only thing left now is the distributor itself - e.g. a problem with the reluctor. However I am fed up at this point so haven't decided what to do next. Besides, I'm tired of 4 cylinders. I want a V12. :woot:

One thing I noticed today was that the rythmic tacho fluctuation we were discussing did not occur during the first 5 or 10 km after starting off from cold. That would tend to confirm the lock-up clutch as the cause because it is not supposed to operate until the transmission oil has warmed up.

Coldy,
I understand yr frustration.
As I see it, there is still NO diagnosis, and until there is one, the problem will persist.
In my world I dont spend money on a problem until I have a diagnosis.

One thing about your problem that still worries me is that I hypothesise that your fuel mixture is too lean.
Why do I say that.
Because you say that whatever you have done, your fuel consumption in the country is only 10 L/100 Km.
I think that is too low. We also know that most other magnas use more than that.
Ask on this forum to find out. I'm getting around 12.5 L/100Km and I drive more country miles than stop start city stuff(a bit like your situation)
Also, we know you have no trouble when the engine is cold and with the engine in this state, the mixture is generally richer.
To test this theory, can you think of a way to inject more petrol, or to reduce the amount of air into the induction system.
To increase the amount of petrol: tip some fuel down the throat/ rig up a small container and suck fuel into the induction system using manifold vacuum from around the air cleaner some where, or just use the accelerator pump more.
To reduce the air supply you could: block off the air supply from the aircleaner system into the manifold/ or you could set the choke flap to a more closed position to see what happens

If the lean mixture theory is correct, it could be due to a carby assembly problem: such as a failure somewhere of the sealing between the top and bottom half of the top to the body or a jet restriction.

BUT whatever: dont let the bastard get you down.
rumpfy

One thing about your problem that still worries me is that I hypothesise that your fuel mixture is too lean.
Why do I say that.
Because you say that whatever you have done, your fuel consumption in the country is only 10 L/100 Km.
I think that is too low. We also know that most other magnas use more than that.
Ask on this forum to find out. I'm getting around 12.5 L/100Km and I drive more country miles than stop start city stuff(a bit like your situation)

I don't agree. Yes, in the city, 12 to 14 litres per 100km is fairly normal even if horrid by modern standards. For easy country cruising though, I don't regard anything worse than 10 litres per 100km as acceptable. I always got better than that with my TM and used to count on at least 660kms per tank before the reserve light came on, after which it would still do another 50+ km.


Also, we know you have no trouble when the engine is cold and with the engine in this state, the mixture is generally richer.
To test this theory, can you think of a way to inject more petrol, or to reduce the amount of air into the induction system.

I figure I'm already doing that by blipping the throttle, thus activating the accelerator pump. However I could try whipping the top off the air cleaner and partially closing the choke. Disabling the hot idle compensator would also be easy. Nevertheless I don't think the engine is exhibiting the symptoms of running too lean. It has plenty of power when called for and the rough running does not occur when under load, only when idling and starting off when hot.

I have the wagon up on stands now, ready to start removing the exhaust system and then the efi gear. I've already loosened the exhaust manifold but fired the engine up today before removing the last couple of manifold bolts. It runs nice and smooth.

Because you say that whatever you have done, your fuel consumption in the country is only 10 L/100 Km.I think that is too low. We also know that most other magnas use more than that.
Ask on this forum to find out. I'm getting around 12.5 L/100Km

Not too low. Did 1800km last week and the last tank i refilled to the brim and had done 572km and it took only 51.69 litres to top back up!! approx 11L per 100km . Speed was very rarely under 110km/h as all freeway work. Wagon was also well loaded. When car is lightly loaded ans speed at 100km/h i get 10 litres per 100 easily. Cheers Vee

http://www.aussiemagna.com/forums/showthread.php?t=91232.

the old girl dont drink much lol

Looks like my TP is a thirsty one! At 10/100 Km; I'd be rapt.
Any way Coldy just have a look at this. This is about all I can say. Just about all I know.

Carby generates a balanced air/fuel mixture over a wide operating range and uses various vacuum signals to control several functions. There are several vacuum motors which are diaphragm operated. When new, these motors don’t leak air but after years of use, may start to leak air and this may upset the air/fuel balance and cause running problems.
Vacuum systems need vacuum gauges to diagnose.
A water gauge manometer can be constructed quite simply from clear tubing bent into a U shape. The height difference under vacuum gives the pressure being measured. For a pressure of 1 kPa, the height difference is 10.2 centimetre. For 10 kPa, the height difference is 1020 mm. This is not a lot, but can be useful for low pressures/vacuum systems. The manifold vacuum at idle is probably around 70 kPa. At this level of vacuum, the precise value isn’t often needed and an inaccurate gauge is good enough. Maybe a normal water pressure gauge like used on water pumps with the needle offset to say half scale, would function as a vacuum/ pressure gauge.

The vacuum piping diagram in the Magna TP manual is drawing No. 257/235/LD13.
Using this diagram, we can see the affect of leaks in the various components.
The ‘vacuum outlet’ is a 4 way distributer, and leaks into this system can affect the idle and running mixture.
Check:
1. Diaphragm of the Air conditioner ‘Idle-up’ ; NO leaks
2. Both diaphragms of the ignition distributor ; NO leaks
3. Diaphragm of the ‘Air Injection Valve’ ; NO leaks
4. Diaphragm of the ‘Purge Valve’ (Control line from the 4 way distributer): NO leaks
5. Leaks around the ‘Thermal Valve’: NO leaks
6. Faults around the air cleaner assembly, whereby excessive air is inducted into the manifold through the 4 way distributer.

Faults around the Charcoal canister are not likely to affect idle performance because fuel vapour from the canister re-enters the induction system only when the throttle is opened.
The BVV should be ruled out as a problem by testing for vacuum tightness at the BVV/ Carby connection as per the manual.

When testing for leaks at the ignition distributor, test manifold vacuum at idle and then block the vacuum line from the distributor to the 4 way valve. The manifold vacuum should not change significantly. (should not change by more than say 2 or 3 kPa at the most)
Similarly with the Thermal valve on the AIJ. Block the line from the 4 way distributer to the AIJ and the manifold vacuum should not change.

The Thermosensor (air cleaner) has two calibrated ports of around 0.055 inch diameter. Similarly, the ‘Hot Idle Compensator’ has a calibrated bleed. (Not sure of the size of the bleed!) These bleeds should be checked to make sure they haven’t been enlarged by some prior fiddler.
Checks on the 4 way distributer can be done without removing it. Just monitor vacuum levels around it as it warms up and block the connecting hoses when it should be shut to check the change in vacuum levels between the ‘blocked’ and ‘unblocked’ states.
The drawing shows a second 4 way distributer connecting to the EGR system.. This vacuum system provides a vacuum proportional to the amount of opening of the throttle flap. Again, there should be no leaks in any component attached to this vacuum source, but vacuum will only occur at increasing throttle opening. A water manometer could check vacuum levels in this part of the system (probably up to 15 or 20 kPa).
rumpfy

Rumpfy, thanks for that list. I'm about to head off to Gunnedah today so don't have time for a proper reply now or to test anything else before I go. However I will get back to you here in a few days.

For now, I can say there are a couple of things in your list I hadn't thought of, e.g. 1 and 2, although I did check that the distributor vacuum cans hold vacuum. Items 3,4 and 5 can definitely be ruled out.