850 10v weird starting and idling problem
 

Hi all,

I have a 1995 manual 10v 850, about 100k miles with a peculiar problem. The car has issues starting after it has just been turned off, if I turn the key the starter will engage and the engine will fire, but often it will lose rpm and stutter a bit about the 300rpm mark before it dies. If I try starting it again straight away it often will not even fire. I generally have to wait about 5mins before I can get it started again on a mild day. On warm days the problem is exacerbated. I have also had it stutter and die when slowing down, I dip the clutch at about 1500rpm and it will just cut out after it has coughed a few times. Again I have to wait about 5 mins depending on how warm it is outside before I can get it started again. It also won't start if the air temperature is above about 85F. Apart from this it runs fine!

My suspicions thus far have been the MAF (which it turns out the 10v doesn't have I'm fairly sure), crank angle sensor, MAP, idle control valve, idle stepper motor or maybe even something to do with the thermo fan? I don't know where to start really. I have taken the car to a few mechanics who just shake their heads as there are no error codes coming up.

I also had a go at setting the air temp sensor thermostat in the bottom of the airbox to permanent cold air, which has improved the performance a little but hasn't fixed the problem.

Any ideas?

Cheers,

Pat

Three things come to mind.

The coolant temp sensor at the thermostat
Bad injectors
Fuel system (too much or too little pressure)

If it runs better with this modification than it's likely you are getting too much fuel. Could be the coolant temp sensor is starting to fail and telling the computer the engine is colder than it really is and causing a rich condition.

Do you have a check engine light on?

Thanks for the input guys

The check engine light hasn't come on, the coolant temp sensor sounds like a possibility, the way it behaves when I try to start it seems like it's fuel related. Do those sensors have a history of playing up in these cars?

Pat

From cruising posts here I haven't seen anything that would make me think the CTS fails any more often than any of the other items you are suspicious of. The CTS is just another part in the system. The thing about the temp sensor is that if it's reading 30 degrees colder than the engine it will flood the engine and if it's reading 30 degrees higher it will lean it out. In both cases it might not set a check engine light because it might still be in the operating range of what the computer thinks is acceptable but the engine will run like crap. Thus, no check engine light but a component causing a problem and is going bad just not bad enough yet to trip the light.

Maybe fuel pump! When it heats up it cuts out! They have a thermal cut on them! If it overheats it will shut off until cool enough to run? Just a thought!

Well I managed to fix the problem. Correct in thinking it was fuel related, ended up being that pesky fuel pump relay. I had partially dismissed this problem earlier as i was under the impression that the faulty relays fitted at the factory were green in colour wheras the one in my car was pink. Turns out the pink ones can fail as well. Interestingly the replacement is made in Hungary.

Thanks for your input everyone