1991 Sunbird 3.1 starts easily, runs nicely for a

[hal.lyman]

1991 Sunbird 3.1 starts easily, runs nicely for a few minutes, the dies. Restarting thereafter progressively produces worse results, harder starting, rougher running, less and less time till it cuts out. Thoughts?

[caffeine]

O2 sensor?

[TexMedium]

I had the same problem on a 1991 Z-24. "Eventually"... i figured it out to be a bad injector, really low resistance. The ecm kept turning down the fuel to bring the to bring the A/F in line until it shut the engine off. Pop the upper intake and ohm out the individual injectors. Good luck.

[robertisaar]

could be either, really. or a failing coil/ICM.

unplug the O2 sensor, try and run it, you'll set a SES light, but if that's the problem, it won't reoccur.

the injectors used on the 2.8/3.1 failing is fairly common at this point, you may have to get the engine warm to see the injector(s) test badly, they could test well when cold.

[caffeine]

Unplugging the O2 sensor could also cause the engine to run better if the problem is a faulty injector.

[hal.lyman]

Wow, great info...thank you! I'll be back with updates when I have time to try these tests...thanks!

[hal.lyman]

How do you 'ohm out' injectors? When you say upper intake your talking about the upper plenum right?

[hal.lyman]

Found an article (series of articles) that explains testing the resistance across fuel injectors:

http://troubleshootmyvehicle.com/gm/3.1L-3.4L/index-of-articles-2

Also I haven't had time to get under the hood yet but I just started it and gave it gas before it was good and warm (last time I let it idle for awhile before giving it gas) and it was hesitating and smelled like a rich mix with unspent fuel coming out the exhaust. Does that help pinpoint O2 Sensor vs. Bad fuel injector?

[Purple pit]

Change that O2, get a Denso if you can. Have you tried some Sea Foam in the tank yet?

[Heartbeat1991]

Could be a plugged up cat, too. When they get hot, they can choke it out.

[Purple pit]

If it's rich all the time it could be the coolant temp sensor. I always say O2 because that seems to be what many overlook. Oh and if you have a cat converter on the car it's trash now.

[hal.lyman]

I think it is the coolant temp sensor! I think that was the one wire I couldn't figure out where to put back after I finished replacing the o ring on the oil distributer!!!!

[hal.lyman]

First thing tomorrow I look here to make sure I did (didn't do?) that!

[hal.lyman]

I had it plugged in....I did unplug the O2 Sensor and it ran much better! I would have let it run longer but it started smoking, I think it's where I sprayed some solvent and it just needs to burn off, all the same I don't feel like playing fire fighter today, but it looks like changing out the O2 Sensor might do the trick!

[Purple pit]

That's good, love an easy fix! Just remember to change the oil. That stuff has to have a good amount of gas in it.