Code 35 Questions (Page 1/3)
MERATIME JUL 13, 09:23 PM
Hello folks

I have an 87 Pontiac Fiero SE with an Iron Duke engine. A couple weeks ago I had a code 45 and I was reading Ogres postings and he mentioned that I should change the map sensor. Sure enough after doing the testing, my map was bad it was the original one from 1987. Besides changing the map, I also installed a brand-new IAC & PVC valve. I cleared the codes and with the new parts installed I took the car out for a test drive for while for the computer to reset. The CEL came on twice after a half an hour drive. when I got back there was a code 35 this time I’m going to check the vacuum lines. But if anybody has any other ideas of what could cause this Code 35 after a Code 45 no longer there, that would begreat, thanks.
Patrick JUL 13, 09:31 PM

From Here...


quote

Code 35 - Idle Speed Error

The ECM will set code 35 when the engine speed is 75 RPM above or below the correct idle with closed throttle. This condition must be met for at least 45 seconds before the code is set. If idle speed is too high, check for vacuum leaks. If idle speed varies up and down, your engine might be running too lean (high air/fuel ratio). Check for low fuel pressure or water in fuel. If idle speed is too low, your engine might be running too rich (low air/fuel ration). Check for high fuel pressure or leaking/sticking injectors. Also, check all connections to the IAC and replace the IAC if necessary.
MERATIME JUL 14, 01:34 AM
Thank you, Patrick for this information. Just an added note: When I started the Fiero today from a cold start, it started up without revving high. Even though the vacuum hoses were changed earlier this year without this problem, I plan this week on changing the vacuum hoses again.

[This message has been edited by MERATIME (edited 07-14-2025).]

MERATIME JUL 27, 05:20 AM
Hello all,

After receiving this code 35 error, there’s now a new IAC valve , I replaced the vacuum lines, I installed a new injector and had the battery tested which resulted in a bad battery and I have had that replaced today with a new one. However, after all these additions installed the car cranks but won’t start. Any suggestions or help would be greatly appreciated. Thanks.
Mike in Sydney JUL 27, 07:41 AM
Do you have spark? If not, suggest you check the ICM.
Patrick JUL 27, 11:27 AM
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Fuel pressure?

[This message has been edited by Patrick (edited 07-27-2025).]

MERATIME JUL 27, 02:28 PM
Thank you guys for responding. I am the only one working on this car and when I hear the crank without the running, I then walk back and I smell a slight exhaust smell. Could that mean there is a spark?

I will go and buy a fuel pressure meter and test it.

Thanks Mike & Patrick.
Jorgens JUL 27, 05:22 PM
since you changed the IAC, I would start there? Since code 35 states the IAC, which you said you changed. It could be a bad part? damaged wires or connector from install somehow? I know the IAC on the 2.8 was only $7 from rock auto, maybe just try another?
MERATIME JUL 27, 07:48 PM
Hello Jorgens,

I have tried two new ones and still had code 35. At each time after removing both IAC’s, they both seemed to have the inner spring area not moved (spring not extended) or do its job while installed and plugged in. Is there a procedure that I should know about installing a new IAC besides measuring to make sure the IAC spring components are under 1 inch?
Mike in Sydney JUL 27, 08:52 PM

quote
Originally posted by MERATIME:

Thank you guys for responding. I am the only one working on this car and when I hear the crank without the running, I then walk back and I smell a slight exhaust smell. Could that mean there is a spark?

I will go and buy a fuel pressure meter and test it.

Thanks Mike & Patrick.



Try using starting fluid. If you have spark, the engine will fire but not run continuously. This would be an indication that the fuel system may be problematic as Patrick is indicating. A faulty or failed fuel pump will cause the car not to start. That’s what happened to me and I had to replace the fuel pump.

BTW, can you hear the fuel pump prime when you turn on the ignition but not start the car? You should hear a quiet whine or whir for a few seconds as the fuel pump primes the system.