1988 2.5 Fiero Low Idle (Page 1/2)
Firezappy NOV 13, 03:36 PM
Hello! I wanted to ask about my Fiero, a 2.5 1988. I was having issue with the car having a poor idle and dying when putting the car in gear. It has a new fuel pump along with filter. Also is new wires, plugs, and what I think is called the icm, the name is failing me right now. I also installed a throttle bottle kit and replaced all the gaskets and seals. I sprayed around and I cannot find any intake leaks. I also put in a new map sensor and a new IAC. Now the car wants to idle at like 500 rpm. The second you put it in gear it dies unless I rev it, and it won't start unless I give it gas. Before this happened the car seemed to be backfiring but it was coming out of the top of the engine, out of the air filter cover. Now it no longer does that, but I can't get the idle right. I know it is possible to adjust the idle but from what I read it is a bad idea. Anything I am missing?

Thank you!
Dukesterpro NOV 13, 04:23 PM
Big one,


did you check your base timing. Poor timing can result a low and often unstable idle
Firezappy NOV 13, 04:44 PM
I don't think that I can do much with the timing on an 88 duke. I don't think I even have a distributer. I have DIS Ignition, so basically my ecm handles all that. At least I think. Or am I thinking of something else?
richard in nc NOV 13, 05:51 PM
500 idles not normal?if its an automatic it could be staying in lock up.
Firezappy NOV 13, 05:55 PM
I don't think it's the lock up, it will die after around 5 seconds if I don't keep giving it gas regardless. It goes down to 500, then starts to sputter after a few seconds and dies. The car drives fine as long as I keep holding the throttle some. There is some hesitation to rev though if it is at around 500 and I stomp the gas though. Before I did all this work it always idled around 1000 now that I think about it, even when it warmed up. I may have fixed an intake leak and now it is idling where it is "suppose" to be.

[This message has been edited by Firezappy (edited 11-13-2024).]

Patrick NOV 13, 08:04 PM

quote
Originally posted by Firezappy:

It has a new fuel pump along with filter. Also is new wires, plugs, and what I think is called the icm, the name is failing me right now. I also put in a new map sensor and a new IAC.



There's no guarantee that a new anything is actually working properly.

If all the above have been checked and are functioning as they should, I'd test the Throttle Position Sensor (TPS) next.
Firezappy NOV 13, 09:30 PM
I do need to check, I also need to make sure all the plugs are actually firing. I did put in a TPS, but while troubleshooting stuff I ended up putting the old one back in, which made no difference.
Firezappy NOV 15, 12:43 PM
I just rememberd an important piece of information that may change things. So my throttle body is not the one my engine came with. I bought a junkyard engine because my original engine had warped, before I did all of this the car had a tendency to idle on the higher side. Now that I have replaced all this stuff it wants to idle to low. Once I verify the fuel and plugs are all fine, could I actually be one of the rare cases that I need to adjust my idle ofset screw thing? It is not tuned for my motor, it was tuned from the factory for my old engine.
Dennis LaGrua NOV 15, 01:41 PM
The cam position sensor under the coil pack sets the timing on the 87-88 Duke engines. If it burns out it will set a code but erratic operation may not always be detected by the ECM. My guess is that you might have a fueling problem like a dirty/clogged injector.
Getting back to what I advise people to buy is a scanner that can help detect problems.
If you don't have one it becomes a guessing game.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 11-15-2024).]

Patrick NOV 15, 03:31 PM

quote
Originally posted by Firezappy:

...could I actually be one of the rare cases that I need to adjust my idle ofset screw thing?



Highly doubtful. As long as the butterfly valve is closed all the way without binding, it's probably fine. I suspect you've got something else going on with that engine that's preventing it from idling properly.