ok guys, its been a while since i posted so here it goes. My 89 tpi firebird has a tendency to have high rpms about 1000 to 1500 and wont drop. lately it has stalling out at start up. I have to press the gas for it to stay on. I have no idea whats wrong with it. Sometimes it struggles to stay on and then dies. Any ideas???

 

maybe the idle soleniod needs cleaning or is faulty...
Try cleaning it or checking all conections relating to the idle soleniod...

 

Probably a Vac leak. Check the IAC as per the instructions on this site.

 

I did clean the IAC and even changed out one time but returned the New IAC because it made the problem worse. What other sensor could it be that can cause the problem. What I notice is that in warm tempatures the idle goes up to 1000 to 2000 rpms and in cool weather it ranges from 600 to 1000 and sometimes it stalls out.

 

could be coolant temp sensor.

 

I have changed the temp sensor already, but the funny thing is that the other day my check engine light turned off while I put 87 octane gas could it be the sparkplugs that could be setting off the idle to go crazy?

 

Still fighting that idle problem?

Your Check Engine light turned OFF? Since I'm presuming it was ON, you should have a stored error code. What is it?

 

My 89 IROC had a similar problem with the idle while cold. It turned out to be a vac leak from the HVAC line. It's a hard plastic tube that gets brittle over time and cracks. There is one line from the intake to the heater control and one coming back to the heater control valve.

 

yes, im still fighting my problem, I will check the codes and post them as soon i can. As for the Check engine light, for some weird reason its off then while i drive it, it turns back on.

 

Ok, checked the codes and it gave me a 21, 32, 34, 36, and 45 does anyone know what is causing the problem????

 

21: TPS high
32: EGR
34: MAP low
45: O2 rich

I dunno what code 36 is, but I hope this helps you out some!

Seems to me like the ERG system is the culprit!

 

36 - MAF sensor burn-off circuit

 

does anyone know what is causing the problem

 

Have you set the TPS voltage to something between 0.47 and 0.58 VDC? That's a good start.

 

yes

 

Seems I already have a few indentations in the drywall at about head-level from this one. There must be something I'm missing...

Just to verify:

• Have you checked the connections at the distributor to make sure the ECM is getting the correct reference pulses?
• Do you have any data scanning software or devices?
• If so, can you check the ECM's reported idle RPM versus the tachometer indication?
• Are you using a separate diagnostic tachometer or the dash gauge to indicate RPM?
• Have you checked all engine and ECM grounds?
• Have you tested the alternator output voltage for any AC voltage contingent? You can test the output directly at the stud, with your meter set for a 2V AC range. Anything more than 2.0V RMS is above the factory allowable limit, which to me is already way too high. Anything above 1.0VAC on a true RMS digital meter would be a problem for the ECM from my viewpoint. That would allow over a 3.5V P-P swing above ECM input signals that are already well below that level.
• Have you disconnected the ECM power for a few minutes to clear the memory, then tried running it again?

 

???

 

What does the alt output have to do with the Idle? I have a idle problem and my alt gauge reads kind of high most of the time? Sorry to jump on this thread but good info thanks