Fiero troubles, discussion

[GTRS Fiero]

Posted for a fellow Fiero owner, from the club email:

The summer has been tough, for me and my car.  I had to miss the 35 Anniversary in Peoria due to my troubles.

Cliff notes version: when I punch the car to get out of the way, the car blows enough fuel injector fuses to disable its thrust, throws the check engine light shortly thereafter and my Chevrolet dealer has had the car trying to get it back in working order since July.  4 specific events to recount in greater detail.

Started with a check engine light.  On the way to the dealer, had to round a trash truck during rush hour.  Got by him, but after the push, the car’s exhaust system took a lower pitch, the RPM gauge went jumpy, and I limped to the dealer repair lot.  They said I blew metal out of the catalytic converter, and they replaced it. $$$.

Out from repair, I drove the car briefly, and the check engine light came on again.  Again low power, limped back to the lot… They said I needed to replace the EGR valve (engine gas recycling).  OK, but not so easy – its hard to find.  They found one but it cost me Peoria…  Drove it some more and the service engine soon light again came on. This time they said I needed the EGR solenoid, often repaired in matched set with the EGR valve, and equally hard to find.  But they did, and replaced it.  Again they said the process caused the car to blow fuel injector fuses.

Driving the car then (after my emergency appendectomy, yes me) they announced ready to pick it up.  Crossing a dangerous intersection, I again punched it… immediately felt something went wrong, and again the car lost power and barely made it safely to the other side of the impasse.  This time, they said, yes it blew the fuses some of the fuel injectors and now recommended replacing the ECM (engine control module – the computer).  This would also be hard to find, and a bit costly…  Well go ahead… the car is worthless not running safely…  Took 3 replacement parts till they found one that brought the engine back to working order, and fuses replaced – good to go.
 
Well, a week driving it like a nervous driver – gently motoring – all went well.  Till yesterday, leaving a parking lot with some friends watching, thought lets punch it…  You guessed it… immediately felt that sorrowful limp, hesitation, pitch change in the exhaust, and a jumpy RPM meter…  and a scary ride carefully watching my idle to get back to the dealer lot for yet another attempt which is where it sits till Monday when ‘the guy familiar with the car’ returns to work.

I’m frustrated.  Does anyone have a clue to help me help them.  I like to drive not get under the hood… The car was running beautifully and is a terrific car I’ve shown, driven in parades, folks love seeing it!

[GTRS Fiero]

My thought would be to take the Fiero somewhere else.  Nothing about the EGR valve should blow injector fuses.  Nothing about the EGR valve would cause the cat to blow out metal.  The shop obviously did not road test their work, nor did the shop apparently do a proper diagnostic, nor did they understand the problem, nor did they apparently ask discovery questions.

EGR valves are available from TFS and local retailers.

There is obviously an electrical short, I would guess in the wiring harness.

Whatever is happening, it's good after the ECU is reset, until the engine is put under a load.  Perhaps the harness is getting pinched, or there is a ground mode.  The ECU goes into I guess limp mode.

I wonder if just 1 injector fuse blows.

No word on the actual code(s).

Anyone else have ideas?

[Raydar]

The power to the EGR solenoid is supplied by one of the injector fuses. There is one fuse for each bank. The replacement solenoid could be bad, or there could be (as you said) a problem elsewhere in the wiring, or even a shorted injector. If you can remove the fuses and unplug the EGR solenoid, and get an ohm meter across the injector circuit, you should measure 4-6 ohms. (Three 12-16 ohm injectors in parallel.)
If the writer is not in an "emissions" state, the easiest thing to do would be eliminate the EGR system completely. INCLUDING HAVING IT REMOVED FROM THE PROGRAMMING.
Of course <ahem> that only applies for off-road use only. I certainly wouldn't want to suggest doing anything illegal. 

[GTRS Fiero]

The first time, the EGR valve was replaced.  Sure, even new EGR valves can be bad, I just don't understand why the EGR valve itself could blow the injector fuse.  I understand about the solenoid.

[Raydar]

The first time, the EGR valve was replaced.  Sure, even new EGR valves can be bad, I just don't understand why the EGR valve itself could blow the injdctor fuse.  I understand about the solenoid.

The EGR valve didn't blow the fuse. They're throwing parts at it.
Whatever is blowing the injector fuse (the solenoid was maybe a good "guess" - although apparently wrong) is the root cause.
The blown fuse is the cause of the "reduced power" complaint, as well as the check engine light, since it also kills the EGR solenoid.

I can't say that I've ever seen a shorted injector, but that would be my next approach.
Individually, they measure about 10-16 ohms (ballpark). I would be inclined to remove the upper intake, and unplug all the injector connectors. Measure each one individually, with an ohm-meter. If one or more of them reads a markedly different resistance, it's probably the culprit. 
It's only blowing the fuse when the throttle is "exercised" because more fuel requires a longer duty cycle ("on" time) to the injector. Thus a higher average current drain.

Three injectors and the EGR  solenoid are ALL that are on that fuse.

Edit - There should be a flat connector (on some 88s, it might be sort of square) that connects the injector harness to the rest of the engine harness. It will usually lay somewhere near the thermostat housing.
It might be worthwhile to unplug that harness, and make sure there is no corrosion bridging any of the pins together. Not likely, however.

[GTRS Fiero]

Fierofool, I think we have something.  Maybe one of the officers would reply to that man's email?

[Fierofool]

I'll link Jenn to this thread.

[GTRS Fiero]

Thanks.  Yes, a link would be best.