Vehicle: 88, 2.5L, 5-speed

Some background info:
My fiero stalled one day and would turn over but die right away.

I replaced the computer from Autozone (this could be the issue), but was still having the same problem.
Unfortunately, I neglected the fiero for some time after getting another car and the return period is more than likely over and I already gave them my computer.

I later found out I had a vacuum leak to the MAP sensor and once repaired the engine fired right up.

This is where I'm a bit hazy. I don't recall if the SES/CES light was on when I first cranked the engine over with the new computer of if it came on a day or two later. At this point I noticed a few things:

1) The light stays on from the moment I crank the engine over thus I can't pull the codes

2) The radiator fan also turns on upon start up and stays on.

3) I pulled the IAC valve and replaced it with a spare I had. I seated the IAC and upon start up the motor reved to redline. I then tried yet another spare and found the same thing. With the IAC valve out and key turned to the on position prior to turning over, both spare IAC's did not self adjust. I thought it was supposed to per an old post I read about regarding achieve the perfect idle. It's as if the motor never goes into closed loop.

4) If I floor it, the engine horribly stumbles with a resulting backfire. I can only get up to speed using partial throttle.

5) I thought I saw the check engine light go off when I ran over some railroad tracks, but mayhave just imagined it

Any tips or suggestions would be greatly appreciated. Thank you!

The fan will run when the ECM is in limp home mode, that is normal for all cars with a computer controlled fan, I think 88 was the only year for the Fiero, but I really dunno, just know thats normal.

The SES light is probably staying on because there is a constant fault. You need to jumper pins A and B of the diagnostic connector. Its located in the center console, just behind the cigarette lighter plate. Jumper those 2 pins, turn the key on, but leave the engine off. It will then flash 12 three times, followed by any error code three times, when it is done, it will flash 12 again.

Take those error codes and start your diagnosis. If you are getting a constant SES light, there is probably a hard fault somewhere, so it shouldnt be too hard.

I dont know what to tell you about the IAC motor. Usually if you turn the key off for a few seconds (say 30 to be safe) then back on, the IAC will home, that is extend as far as it can, then retract a set number of counts. This will cause the pintle to pop out of the IAC and go flying across the shop if you dont restrain it. You should also hear the fuel pump kick on for 2 seconds. If you are not getting IAC movement when homing, or with the engine on, remove the ECM and test for continuity from the IAC plug to the ECM on all 4 wires. Check GMtuners.com for pinouts for the ECM.

You can try starting the motor with a dummy IAC in the motor, then hook up any known good one outside the motor, keep a little pressure on the pintle so it doesnt fully extend and pop out, then take off a vacum line. The engine should rev up a little, the ECM will see this and try to compensate by reducing air, the IAC pintle should extend.

1) You shouldn't be pulling codes with the engine running, instead with the key on in "run" position and the engine off.

If you get constant fan and the AC isn't on, it sounds like you didn't pull the chip from your old computer, and if you did, its either inserted improperly or only partially.

On the SES... Yes turn the car off. Then insert the code key or jumper the terminals as said above. Then turn key to accessory on front position and the SES will flash once then two times pause then again... 3 times the code 12. Then it will flash the codes the same way. 3 times till it moves to the next code and the next... Its done giving codes when it gets back to the code 12...

Worse case call Autozone and find out what the warrenty period is on the computer. Even if you don't have your reciept they should have you in the computer. I thought is was a year on a computer, but I'm not sure.

I have had 3 computer failures in my two 80s cars.
On the bird...
the curcuit on the fuel pump failed. We used the manual to trace the code and it lead to the computer in the end. New junkyard one and the car was fine. Then that one failed with a no start and lack of SES light. The diagnoses jumper would not communicate with the computer and would not flash 12 or any codes. I threw my old one in to check to be sure the SES was not faulty and the old computer went thru the test fine, so I knew it was the new junk yard computer. So I got an Autozone one. All was well.

On the fiero...
I was driving and had a code trip and kill the car. Car was bucking and farting something aweful and it would stall. It would not run longer than 30 seconds. Took 20 minutes & about 20 starts to get it .25 miles to the nearest gas station. I had my jumper tool and tested it on the spot. It would not run the test. NO code 12, no flash at all. I let it sit about 30 till help arrived. The computer cooled down enough to limp me home before the bucking started again. Autozone computer swap and all was well.

So 2 Autozone units that are still going strong... The bird's computer has been in for about 5 years & the fiero's 1.5 years.

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"I'm just a girl..."
1984 Indy Fiero Pace Car
1987 Red & Black Firebird: "RAIF" WEBSITE: www.redraif.com
OTHER CARS’ WEBSITES:
1982 Trans AM / 1990 Chevy Dually / 1976 Scout II / 1987 Nissan Pulsar

Hello 86GT3.4DOHC, KurtAKX, & Redraif;

Please accept my apologize as I feel like a jerk for not replying. I wanted to reply, but have a health condition that presents itself occasional making it extremely difficult to do such simple task such as shifting or even putting on a shirt. As of this Friday, I've seem to have healed quicker than usual and got to play around with the fiero some more.

I believe I incorrectly conveyed my actions as I am not attempting to get the fault codes with the engine turned over. I only turn the key to the position just prior to starting. I've done this may times over the years on several fieros so it's not new to me. The problem is because the SES light is constantly on I can't pull the codes. The check engine light will not flash, it just stays on and this is with the Pins A & B jumpered.

I removed the chip and replaced it as KurtAKX suggested, but it didn't seem to make a difference. And yes, I was very static conscious while putting it in old chip and even grounded myself prior to putting it in.

I started her it up and removed the TPS and rotated it and it did not seem to make a bit of difference The only sensor that seemed to respond to me unplugging it was the MAP. I decided to stop though as the I later noticed my exhaust manifold glowing cherry red. I'm totally stumped as to what is going on.

Redraif; The only reason why I thought it might be the new computer is that they may have given me one from an automatic or one from an 84-86 with dist (if it's even possible.) The latter It's probably an incorrect assumption on my part as it does drive.

Off Subject Section:

86GT3.4DOHC & KurtAKX, it's good to see you 2 are still on board. It's been some time since I visited the forum. I got pulled into the Turbo Nissan scene, but missed my Fiero.

Anyway, something of interest I got to drive my first 3800SC auto today It's in an 88GT. It's got some issues, but drives and rides very nice. The fellow was offering to sell it for $4900. He offered to let me take it out by myself (gotta love fiero guys but I just didn't feel right about doing so and asked if he would go with me. I didn't really get on it except for once and once it down shifted it pulled pretty good, but the RPM tack jumped to 6200 and I let off as I wasn't sure what the redline was, not to mention it wasn't my car.

The Bad: The car's got a few issues such as un-uniformed wiring that with no protective loom, Cracked front window, rear light assembly, missing ligts (he did a Z28 light conversion placed in the front turn signal indicators,) bad paint, missing front left side indicator, and somewhat crude exhaust. He also mentioned the AC works, but is missing one hose, but says he can fix it prior to selling the car. The speedometer is also off and bounces around like mad (tach fiter perhaps) but he said it was just wired up incorrectly and would also fix it prior to selling in.

The Good: Owner says the motor/trans/supercharger/brakes/absorbers were all recently rebuilt with about 2000 miles. Polyurethanes on all the suspension components. Car drives pretty smooth and seems to have decent power, not to mention the cool sound of the supercharger.

Given my somewhat chronic health condition I have been considering getting an automatic for some time and as I told one of my best friends that if I'm ever getting rid of my fiero, it's because I'm getting another one

P.S. The owner seems to be an forum member. I forgot his name, but said he got the mounts from Purple Reign and got the computer reprogrammed from another forum member. He also mentioned he was able to make it to the last Daytona show so some of you may know who he is.

I have the funds but would have to get rid of my current fiero and doubt I would get too much for it Anyway, if anyone is interested the 88GT, black, 3800SC, autois on Craigslist in the Tampa Bay area. If I don't end up getting it, I would at least rather another forum member pick it up.

Try grounding pin A then, maybe the ALDL ground is bad. Actually, it might be pin B, I dont remember off hand, ground them both, it wont hurt.

If that doesnt work, figure out which is which and check for continuity to ground on the ground wire, and check continuity to the ECM pin on the one that goes there.

Hello 86GT3.4DOHC;

I tried grounding both pins and still the SES light remained on

I'm not exact ally sure how to ”check for continuity.” Is the idea to make sure there is not break in the line:? Do I use an OHM meter? Thank you!

If you have a multimeter, set it to check for resistance, so when you touch the two probes it beeps (or if yours wont beep, it reads 0 ohms). Then remove the ECM, this is very important, you should never measure resistance through an ECM. Remove the ecm. find out which pin goes to the ALDL (www.gmtuners.com for wiring diagrams) and put one test lead on the ECM connector and the other on the ALDL pin. If it reads 0 or close to it, your ok. If it reads OL or whatever it reads with the leads not touching eachother, then the wiring is bad.

If the wiring tests good, its probably a bad ECM

I was looking at the Diagnostic Chart A-2 in the Factory manual, for problem "No ALDL Data or won't flash code 12 Service Engine Soon light on steady".
You should be able to check the SES light as 86GT3.4DOHC suggests without the use of meter.
Revised steps from chart - Ignition "OFF", disconnect Negative battery cable, disconnect ECM connectors, reconnect Neg. battery cable, Ignition "ON" - Note SES light.

If light stay "ON", then there is a short in control wire circuit to the SES light.
If light goes "OFF", then the chart lists testing for problems with ALDL terminal B circuit, or the PROM.
**** NOTE: The Diagnostic Chart leaves out the step of removing the negative battery cable first, before removing the ECM connectors. ****
In another section of the manual, under ECM service, the first step is to disconnect the Negative battery cable.

A meter or a continuity test lamp will be invaluable for tracking down an electrical problem; both can be had for a minimal investment.