Ok, I thought I could fix this but I guess I am going to have to ask for help! I have an '87 elke with a 4.3 and automatic trans. It runs great most of the time, but will frequently start running rough, and die at idle. It re-starts, but is embarassing and a nusiance. It only does it after it warms up to operating temp. A little background, I replaced the thermostat with a 180 because the 195 made it read hot. I replaced the TBI with a new one, but it is listed for a '91 4.3. Everything hooked up except I had to replace the ISC connector to accomodate the later style motor. Today I replaced the distributor and coil with brand new "performance" ones from Summit. Runs smooth except when it goes into it's dying mode. I am at a loss what else it can be. Fuel filter??? I am now looking at "WAG" ideas. Any help would be appreciated!!! :dontknow:

Was it doing that before you installed your new dist. If it was we can rule out distributor problems

Yes, it was.That's one of the reasons I installed it. I have also cleaned, but not replaced the EGR valve. I ordered a new one just in case.

Could be low on tranny fluid, if it idles low and dies while in gear with foot on brake after warm up.

I was going to suggest to check your EGR valve. EGR will sure cause the problem you describe. The reason it waits till its warmed up is because is the EGR vacuum is delayed if hooked up properly to thermo vacuum switch not allowing vacuum until operating temperature. Cleaning it did not make a difference? Do you have a Vacuum Pump??? If so, start it up, give the pump a couple of shots and the motor should severely stumble or die.

It can also be dirty to the point the pintle is slow to allow the valve to shut back off at times. That could explain why the problem is intermittent. It might not be a bad idea to replace the EGR valve if it’s old and consider it maintenance if it doesn't fix the problem.

If I pull and plug the vacuum hose off of the EGR valve, it will barely run. Can I somehow eliminate the EGR??

Sounds like you might have the wrong vacuum port going to the EGR valve. You shouldn't have vacuum to the EGR at Idle. If you do the EGR valve is opening at idle causing a major internal vacuum leak. Just keep the EGR unplugged from vacuum source right now. If it can barely run now, then go from there. Check your firing order, raise the idle screw up a bit, set your timing, adjust the carb or whatever you have to do to get the idle to smooth out and come up, and then adjust the idle.
Obviously this motor has sat for a long time. It’s probably not a bad idea to take the EGR valve off and clean it to make sure its closing off completely at idle.

Sounds like it might be your carburator. The float could be getting stuck and flooding the carb.

Isn't the 4.3 a TBI engine?

Good Catch. Yep, he mentioned its TBI .

Yeah, it's TBI. It has a 200 transmission in it also. I have some scattered info that says this tranny sometimes doesn't come out of lock-up, and will kill the motor. Anyone know about that? How would I test that, and what is the fix?

There's an electrical connector on the side of the trans, toward the front. Disconnect it and you will be disabling the lockup function. You can plug it in again once your diagnosis is complete or just leave it disconnected with no harm other than a slight fuel mileage decrease.

Bill

Is it dying with the tranny in neutral or park?
If so the problem may be the IAC(idle air control valve).Another possibility is the EGR is stuck open or the idle solenoid is not working.I'm sure that I'm missing some other possibilities so keep an open mind.

It only seems to die in drive, at stop lights, after it warms up and has been driven for a while.

That does sound like it could be the lock up. Not downshifting when you come to a stop. I was having the same problem after highway driving when slowing down in traffic too. Unplug the lockup as mentioned above and check in Transmission and driveline forum for the fix. There is a current thread on the very subject started by Trannymike.

Good luck with it! :beer:

Thanks evreyone for all the help! :You_Rock: I unplugged the connector at the trans, and it no longer dies! Still idles really low, perhaps this is normal?

Hook up a good timing light to get accurate RPM's and (with help) check idle speeds normal, in gear, and with A/C on...Adjust accordingly. Gees I forgot it is an early injection system...I just left the MAP sensor unplugged at the nose of the air cleaner when I had an S10 pickup like that. Then it thinks it is cold all the time and idles faster. I'll shut up now and you can get help from those with more real knowledge on it.

:beer:

Now it sounds like maybe you have timing and idle not adjusted properly,I would make sure it is set according to the emissions sticker and then plug the tranny back in to see if you have the same problem.

Well, there doesn't seem to be any way to adjust the idle...suggestions?

I believe there is a plug covering the idle adjustment screw. Needs to be knocked out to access it.

I will look for it, thanks! I wonder if the computer won't override any changes I may make?