I have an 88 Fiero coupe 2.5 automatic. Sometimes when I come to a full stop the engine stalls, but I can restart immediately. If the car is in motion it will cut out for a fraction of a second and continues to run. Engine runs good otherwise. I also get the rich exhaust code when I first start the car, but never comes back until the next day. I checked the evap canister and changed the o2 sensor with no luck. I also disabled the egr for the stall issue but no difference.

Any suggestions?

Thanks!

cmd88

[This message has been edited by cmd88 (edited 03-15-2021).]

Can be anything w/ loose contacts etc.
Try a few things first....
Remove battery cables, neg then +, then: (reinstall + then neg cables.)
Cleaning/fixing all grounds bolted to engine etc in back of car.
Carefully "remove" lock bolt on C500 and remove/reinstall the plugs several times. Should stir up contacts to make a better connection. Do Not remove the Grease in it.
Do that for other plugs too but maybe not all at same time.
Clean/fix + "Box" under C500. Fuse links etc here can have loose nuts, rotten ends, and more.

And Wires w/ ring ends Bolt on whatever need cleaning and silicone or brake grease to prevent "rust."
See my Cave, Wire Service

Then See my Cave, DIS Ignition and 700 TBI

Could be ECM dying.
Pull console and tap ECM w/ fingers. If affect when car in running... "Dead" ECM. ECM can have crap solder joints etc and tapping may help finding them.
Fiero slowly fries ECM because how installed. See my Cave, ECM Heat
If ECM "bad," save PROM in it and move that to new ECM.

Note:
Stalling when Stopping can also be another problem if have Auto Trans. AT have problems w/ TCC and can stall the car. Unplug the Trans and leave it off while looking. Small Plug is on front of trans case and a bit hard to see. many sure wire won't hit exhaust when off. Plug has a latch and very hard to impossible to see. You should feel it. I believe push in to connector shell to release.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

I was going to suggest the TCC lockup, too.
What that acts like, is the same as driving a manual trans, but forgetting to push in the clutch when coming to a stop. The car kind of shudders to a stop, and then dies. You can put the shifter in N, restart the engine, and as soon as you put it in gear, it may die again, with a loud thump. After a while, it will start and run normally again. Probably until the next time you stop.

As Ogre said, you can unplug the connector, to test. It's a square connector, usually blue in color, on the front/side of the tranny, that points right at the driver's posterior.
Most people just leave it unplugged indefinitely. It will cause a little bit higher revs at cruising speed, and a bit poorer fuel consumption, but not much else. The trans may run a bit warmer due to the inherent slippage of the torque converter, but many have run that way for years, with no ill effects.

Thanks for the info guys! Lots of things to check out. I think I'll start with the TCC since it's the easiest.

cmd88

Stall while Stopping is often AT w/ TCC problems... Not just Fiero but most GM AT cars in 80's because of crappy solenoid sticks keeping TCC applied.

But this "If the car is in motion it will cut out for a fraction of a second and continues to run." is often another problem and often a giant pain to find. You clean/fix above often helps this and other issues/problems.

Example: You replace "1 wire" O2 sensor but "1 wire" is fake because this sensor has "hidden" 2nd tan wire bolted to trans bell or block.
That Tan wire is Not a ground but wired like one. If this wire has crap connection then New O2 will have problems.

DIS brick 2 wire power plug is ground to engine same way.

Leaving Trans w/ TCC unplug...
Driving around town then likely won't notice a problem because TCC often doesn't lock much or any. TCC locks only after meets rules... Over 35mph, even engine load, in 3rd gear, foot of the brake pedal.
Driving on highway.... You will see 200-300 more RPM in 3rd gear and suck gas faster like City Driving. If you're on a trip, expect to loose ~ 4 - 7 MPG and stop more often to buy gas.

Trans will get hotter w/ TCC disabled because can't meet the rules or unplugged. The Coolant System will notice because of Trans heat exchanger in left tank of the rad. If Coolant system has problems, unplugging TCC can make more problems there.

quote Originally posted by Raydar: ... Most people just leave it unplugged indefinitely. It will cause a little bit higher revs at cruising speed, and a bit poorer fuel consumption, but not much else. The trans may run a bit warmer due to the inherent slippage of the torque converter, but many have run that way for years, with no ill effects.

quote Originally posted by theogre: Leaving Trans w/ TCC unplug... Driving around town then likely won't notice a problem because TCC often doesn't lock much or any. TCC locks only after meets rules... Over 35mph, even engine load, in 3rd gear, foot of the brake pedal. Driving on highway.... You will see 200-300 more RPM in 3rd gear and suck gas faster like City Driving. If you're on a trip, expect to loose ~ 4 - 7 MPG and stop more often to buy gas. Trans will get hotter w/ TCC disabled because can't meet the rules or unplugged. The Coolant System will notice because of Trans heat exchanger in left tank of the rad. If Coolant system has problems, unplugging TCC can make more problems there.

*sigh*

A couple more questions about stalling:

Can the stalling foul the MAT sensor? I've pulled it out twice and it was wet. First time I cleaned the sensor and didn't get a 45 code for 2 days driving about 60 miles. Code came back the third day, and the sensor was wet again.. Should I try to fix the stalling before replacing the MAT sensor? I don't want to risk ruining a new sensor.

Can a defective injector cause stalling and rich exhaust?

Does anyone know correct ohmage of injector? 2.5 TBI btw.

Thanks!

cmd88

I had a similar problem with my 88 GT. It turned out to be one of the fuel pump wires inside the tank worked loose. Would cut out intermittently driving me crazy. Once I dropped the tank it was obvious because the wire had worked loose and was now not connected to its terminal. Re bent the connector to make it tight and the issue is now gone.

Rolland

Another one of these rare 88 SE's. I think this is the second one in a week I've seen people posting about. Would love to see one of these mythical beasts.

quote Originally posted by theogre: If you're on a trip, expect to loose ~ 4 - 7 MPG and stop more often to buy gas.

Seems a bit excessive. I've had a bunch of V6 autos and get maybe 21 MPG highway. That estimate would mean I'd get 15.5 MPG highway. I'd estimate maybe 10% loss of MPG Hwy or 1-2MPG.

My bigger concern would be the heat inside the tranny without the lockup.

I should clarify:

The car doesn't stall as soon as I come to a stop. Never has. It's sometimes when I'm sitting at a red light for a minute or so. While driving it might cut out just a short distance from home, sometimes it might be 60 miles before it does it. Totally random. Starting to suspect that 88 debacle of an ignition system.

88 SE: Yeah I posted a couple topics with that error. Forum won't let me edit the titles. :\

cmd88

[This message has been edited by cmd88 (edited 03-31-2021).]

Unplugged and plugged in the ECM connectors a couple times and now the random stalling and code 45 are gone!

Party time!

cmd88

Good catch