Howdy ya'll, have a question regarding my 3.0 in my 95 Sable (sorry, I know it's truck forum!)
Recently I just put in a new engine in the sable, to replace the old one which overheated. The old one ran perfect, no troubles at all. But now when it gets below 10 degrees it doesn't like to start, it acts like its not getting enough fuel, but if you crank on it for more than a minute it will barely fire up. The "check engine" light is always on, approximately 10 seconds after it starts, no matter how cold. When it dropped down to below -25 from work one night the car stumbled briefly and ran fine for about two minutes and the check engine light went off, after it warmed up it stumbled again and the light came on and stayed on. I pulled the codes and it said the IAT and ECT sensor values were out of range, so I replaced them both. Well that worked, with the codes cleared the car ran great, no check engine light or anything, but the minute I unplugged the tester, it stumbled and the light was back on. Sooo...pulled the codes again, but there was NONE! It still starts hard, when cold. Seems to run just fine, the tester indicates the PCM is in closed-loop operation, but it's a pain to start in this winter weather. Any suggestions on where to go now?
Thanks folks, sorry for such a long post.

 

Try resetting your PCM by disconnecting the negative battery terminal, and turn your headlights on. This should be done after changing any of your sensors.

 

I agree with Bob, you should reset the PCM now that you have the new sensors in place. It might be, though, that the IAT and ECT sensor values were both out of range at the same time because the engine wasn't up to operating temperature when you pulled the codes. Possible?

I was thinking some kind of fuel problem, too. You should try and test your fuel pressure when it's cold and then when it's warm.

A bad fuel pressure regulator can sometimes cause hard starts after a long sit.

If it's a fuel starvation thing, maybe try turning the key on and off slowly several times to help prime the system.

If it's a too-much-fuel situation, then you should consider leaky fuel injectors, bad FPR, etc.

And what kind of fuel are you using? Make sure it's a name brand, nothing more than 87 octane.

 

I have had a similar problem with my 97 taurus with the 3.0L vulcan, and it turned out to be the MAF. It would idle really rough when cold, and stutter when in gear. I put in a new MAF, and it worked fine. But when I put in a chip, it started back up again.

 

If it's the MAF like silvapain said, you might try pulling it out first and cleaning it first with some carb cleaner. I don't know if you did that or not, silvapain, if you did, please forgive me for discrediting you, haha.