Car can't drive when cold. only once warmed up. Misfiring when Warm....

[Ryann]

I thought you tested the TPS.

[fiftytakedowns]

False alarm.

Tried driving it today, No luck. I wonder why this is happening. I dont want to start buying parts and throwing them at the car.

[fiftytakedowns]

So today I did a sensor test by

driving car.
unplug sensor
drive again.
evaluate.
repeat.

I did that for every sensor:
Camshaft position
AFM
TPS
TPS and ICV
ICV
O2


Every single time it had the same symptoms.
also every time the car would run alright until about a minute or two of driving, then the misfiring would happen.

[Ryann]

Seems like you've ruled out engine management components. You're down to wiring and mechanical issues.

[fiftytakedowns]

How can I test wiring, I have no IDea how to troubleshoot this way.

Where do I start?
Is it possible that some sensors can be bad even though they tested (resistance) okay?

[RoadWarrior]

I think its the crank positioning sensor. if it was bad it would still not work when unplugged.And we had this exact problem on one of our work trucks.

[fiftytakedowns]

the car cant start without the Crank position sensor? you really think that could be the culprit? I have 2 of them that I have been switching between hard to believe that both my spares are bad.

[fiftytakedowns]

so today I double checked TDC with cams and crank. found notch on pulley etc. etc.

replaced cracked intake boot.
replaced main relay
(both with brand new OEM)

I also took off the crank damper, impacted the mother on and then put on the extra pulleys. I was hoping this would eliminate a vibration that possibly might occur causing screwy CPS signals. just precaution.

I didnt really get a chance to drive it because It kept on wanting to overheat after I put the radiator back in. so I am letting it sit over night, then I will run the car in teh morning with the rad cap off to bleed out the air.


One last thing. There is a temperature sender on the right side of the radiator with a Plug that goes into it a three pronged one. my actual prong holder broke, so all I have is the three wires, and I dont know which wire goes to the respective prong in the plug, so if someone can take a picture of that for me or make a diagram that would be greatly appreciated as I have had that unplugged.

[fiftytakedowns]

Ive got a bit of an update for today.

Drove the car around today after bleeding the system the proper way (from the bentley), and to my surprise the problem is almost gone. I think it is more of an ECU issue at this point because I have three ECU's:

mine stock:
Would Drive and pull normal, but for some reason if you downshifted or started cruising at 3.5 RPMs and then punched it it would misfire or hesitate etc. but it would Drive through it completely normal, and would pull through it as well.

mine chipped
same symptoms, except it would be at 4k RPms, and had more difficulty pulling through it. (still pulling a 1244)

Ryans stock: couldnt get problems to arise.

[fiftytakedowns]

I gotta say, you are turning me against going to the COP conversion...

the m42 coils are just as bad perhaps. I dont even know if it is the coils.

I think Ive narrowed down the problem of the mid RPM misfire and bucking to be an ECU issue, however, The Cold Start Bogging Is still driving me crazy. I have to wait 15 minutes just for the car to warm up in order to drive it.



I pulled the plugs and replaced them with some champion plugs. not the best brand, but I dont want to throw money on a second set of plugs when my old NGKS have less than 10K on them.

anyone think the thermostat would cause the problem of cold starting?

[Jean]

My m20 would bog and die after i did a head swap...it ended up being fuel pump AND air in the system from what I can tell.

Not sure about m42, but M20 motronic system reads from the CPS/AFM/TPS/DME Temp sensors.

Temp sensor is cheap to replace :)
CPS can measure good and still be bad , car will crank w/o CPS btw.

I do have a spare 318is pump you can borrow if you like.

[fiftytakedowns]

My m20 would bog and die after i did a head swap...it ended up being fuel pump AND air in the system from what I can tell.

Not sure about m42, but M20 motronic system reads from the CPS/AFM/TPS/DME Temp sensors.

Temp sensor is cheap to replace :)
CPS can measure good and still be bad , car will crank w/o CPS btw.

I do have a spare 318is pump you can borrow if you like.

Hey Jean,

thanks for that input, I think it would be accurate to say that the car would test couple things good, while they end up being bad. I want to agree when saying that it could be the fuel system, but I was consistently getting 45 PSI when I did the fuel pressure. I am wondering if maybe the computer is telling the injectors to switch off, and what would cause it to do so. (especially when cold)?

I have replace the coolant temp sensor with two other units.

[fiftytakedowns]

What would cause My injectors to turn off or spark to be cut (ONLY WHEN COLD)? anyone know?

[Matt-B]

i have spare coils you can have for shipping, 4 of them, all worked fine on my car, just need to find them...

crank and cam sensors are that much, like 40-50$ from blunt for the non OEM, why not replace it?

[fiftytakedowns]

i have spare coils you can have for shipping, 4 of them, all worked fine on my car, just need to find them...

crank and cam sensors are that much, like 40-50$ from blunt for the non OEM, why not replace it?

That sounds good man, I sent you paypal on m42 club as well.