90 Corsica 3.1 starts but stalls right away

[Lomitus]

Ok, 1990 Corsica LT, 3.1L multiport. A few weeks back I had a hard morning start...figured it was maybe some bad gas or even a tich of fuel line freeze up (it was really cold that morn)...later that morning she finally fired up and I ran her to Sunoco, filled the tank with some 93 octane and she's been fine till this past week. Wednesday on my way home on the highway, the engine started choking and cut out...by the time I got her off the highway though, she restarted and ran fine the rest of the way home. Friday morning went to start her again...engine cranks and -DOES- start, but stalls out after 3 or 4 seconds (pretty much right after you let go of the key) and it's been like that ever since. Oh..sometimes it will let loose a little backfire just as it dies out, but not always.

I've replaced the coil packs, the coil module and the crankshaft sensor. I tested the fuel system...getting a solid 45 psi out of the fuel pump (specs call for 40 - 47 psi) and I've even hot wired the pump directly just to make sure that the relay or the oil pressure switch wasn't the problem either...and the fact that she -does- start seems to suggest that the injectors and pressure regulator seem to be working too. All the wires and connectors look pretty decent too.

And YES the plug wires are all on in the correct order and YES the catalytic converter is fine (can ya tell I've been reading forums all day?). I'm really stumped here...what else could it possibly be???

I would be most grateful for -ANY- suggestions...3 days of busting knuckles and lost time at college and I'm still no closer to figuring this out.

[Lomitus]

Oh...btw...she's not blowing any codes either. I get the "12" that says she's in diagnostic mode and that's it (which I guess rules out a MAP sensor as well as that should blow a code 33 or 34 or something). In fact, I never had the check engine light come on...in any abnormal way at least.

Thoughts...anyone?

[temperingloser]

you need to make sure the coolant temp sensor is working correctly but I am not sure where it is located it may be causing the engine to run rich and there may be 2 sensors one for the gauge and one to tell the computer how rich to run

[Lomitus]

Well for the sake of anyone else out there who may be looking for info on similar symptoms like I was last week, it turned out to be a bad fuel injector after all. I hadn't really suspected the fuel injectors because the car was starting...it just would not run for more than 3 or 4 seconds. I figured if it was starting, the injectors must be working...it just wasn't the case.

The way to check this is to run an Ohm meter across the terminals of the fuel injectors (you may need to remove the plenum to get at them). I'm not exactly sure what the GM factory specs are...mine ended up being between 12.5 and 12.7 ohms, except for the bad one which was 2.1 ohms (I read somewhere that most makers are between 10 and 18 ohms)...but if 5 all read roughly the same and you have one with a much higher or much lower reading, that's your bad injector.

The thing with all of this...at least with the 3.1 in my Corsica (and I would assume this would apply to MANY GM's out there)...is that if one injector on a multiport goes bad, apparently it shuts down the whole freakin' system. It wouldn't be so bad if the injectors were easier to get at (like with a TBI) so you can check them but having them under the plenum makes them really difficult to get at.

Also for the benefit of others, should you happen to be working on a 3.1 liter like mine; good luck getting that fuel injector rail off with the injectors on it if you're going by the instructions in a Haynes manual! While the manual says to remove that as an assembly, I found I had to unclip all the injectors from the fuel rail while it was still on the engine, remove the rail separately, then pull the injectors out individually (and installation was pretty much the reverse...I couldn't get it to go back on as an assembly either).

So hopefully that will help some seeker of knowledge, somewhere at some point. Special thanks to "Tim" of Barry Buick in Lakewood, Ohio for his assistance in troubleshooting this one!

[fixitallright]

Originally Posted by Lomitus

Well for the sake of anyone else out there who may be looking for info on similar symptoms like I was last week, it turned out to be a bad fuel injector after all. I hadn't really suspected the fuel injectors because the car was starting...it just would not run for more than 3 or 4 seconds. I figured if it was starting, the injectors must be working...it just wasn't the case.

The way to check this is to run an Ohm meter across the terminals of the fuel injectors (you may need to remove the plenum to get at them). I'm not exactly sure what the GM factory specs are...mine ended up being between 12.5 and 12.7 ohms, except for the bad one which was 2.1 ohms (I read somewhere that most makers are between 10 and 18 ohms)...but if 5 all read roughly the same and you have one with a much higher or much lower reading, that's your bad injector.

The thing with all of this...at least with the 3.1 in my Corsica (and I would assume this would apply to MANY GM's out there)...is that if one injector on a multiport goes bad, apparently it shuts down the whole freakin' system. It wouldn't be so bad if the injectors were easier to get at (like with a TBI) so you can check them but having them under the plenum makes them really difficult to get at.

Also for the benefit of others, should you happen to be working on a 3.1 liter like mine; good luck getting that fuel injector rail off with the injectors on it if you're going by the instructions in a Haynes manual! While the manual says to remove that as an assembly, I found I had to unclip all the injectors from the fuel rail while it was still on the engine, remove the rail separately, then pull the injectors out individually (and installation was pretty much the reverse...I couldn't get it to go back on as an assembly either).

So hopefully that will help some seeker of knowledge, somewhere at some point. Special thanks to "Tim" of Barry Buick in Lakewood, Ohio for his assistance in troubleshooting this one!

To ADD to this post, I have an 89 Corsica with a 2.8 v-6, and have same problem. It can also be a bad fuel pressure regulator that causes it to start then stall. Or a leaking one through the vacuum port...takes about two min for it to show up with fuel pump relay harness jumped to keep fuel pump running. I too spent plenty of money on crank sensors, modules, coils, and wires before finding this solution. You would think 'THINK' chevy would install a sensor there as well, for they have one everywhere else. Hmmm