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. Hvae you checked your coolant to ecm sensor, also vac hoses?
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01:57 AM
Jax184 Member
Posts: 3524 From: Vancouver, Canada Registered: Jun 2005
Disconnecting the IAC while the engine is idling shouldnt cause much of a change. The IAC will remain in the position it was in, and therefor the engine will continue to run fine so long as it's air requirements don't change. At least, that's what I think.
The Idle Air Control is one I would not unplug while engine is running cuz it uses a driver in the computer like the injectors and it could cause a spike and short out something in the ECM.
Thanks for that info... I will tell Joe "no more random disconnecting of sensors!" LOL!
Oh and I think I found the Idle Air Inlet hole... verification would be helpful... but I think its on the trunk side of the TB where the IAC screws in. Down towrds the bottom right next to the gasket? Yes /no??? If that is it... I blocked the hole with my finger and found no change!
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01:43 PM
Rodrv6 Member
Posts: 1910 From: Ball Ground, Ga. Registered: Nov 1999
The idle air inlet hole is above where the idle air controller screws in. It's not a round hole, but is somewhat "L" shaped and is inside the air cleaner area next to the throttle bore. With a warmed up engine, plugging this hole should cause the engine to idle around 6-700 rpm, not die. If the engine does die, the minimum idle screw has been messed with or the throttle bore is very dirty around the throttle plate. If the idle stays high with the hole plugged, then you have a vacuum leak. One spot I had trouble with on my 84 was the EGR valve bolts working loose. That would cause a 2,000 rpm idle or higher.
------------------ Rod Schneider, Woodstock, Ga. "You can't have too many toys!" 1988 Fiero GT 1966 Porsche 911 Van's RV-6 airplane-under construction
Cool... thanks! Just the info I needed! It would be nice to know if I can rule out a vacuum leak... Will report back once I get home w/ the car warmed up and can check the situation.
Then I can clear the fixed computer codes and start fresh and see what that yields!
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03:24 PM
triker Member
Posts: 454 From: Yreka, Ca. USA Registered: Apr 2000
I'm not familiar with 2.5's so maybe it won't die with the idle air hole plugged but should drop off significantly with it blocked unless you have a large vacuum leak. since you seem to have checked everything in the engine compartment without finding any leaks, I have one more thought, how are your brakes? Try pinching off the large vacuum line going to your brake booster.
So with the code for 15 & 33 pulled I undid the battery. I took a suggestion from another thread about the coolant sensors... the car coded for 15, but I thought it was just when it overheated when the fan quit, so I did not worry about it. Figured I fixed the code. Then I got to thinking and decided to go ahead and replace the ECM coolant sensor on the thermostat housing... Someone had said that could cause an idle up situation.
Then reconnected & started fresh with the ECM... Well the car was still racing @ 3100 after, so I messed with the brake booster and replaced the line with some known good line. Still racing... I tried blocking the IAC hole as suggested... This dropped the engine down to 1800rpm... So it effected it, but did that still mena I had a vacuum leak??? I went over the whole vacuum system with alcohol, even got under adn did the underside of the intake manifold. NADA...
I gave up and went to bed. Figured start over tomorrow. Thought maybe the ECM needed to relearn to accept the new sensor to quit acting up.
So this morning I got up and the car was now idling at 2400.... better... So I drove it about 10 min on the surface streets. Got to I-75 and as I depressed the clutch to downshift the idle dropped down to 800rpm. It stayed there till I moved again. Then it had some stumbles at speed, but did ok. smoothed out the longer I went.
Once I got to the office it was holding idle @ 800, so I assume the sensor was bad and it needed the relearn.
Still never found a vacuum leak... Now...At morning start up the car is idling at about 1800 now. then about 15 mins into the trip it is idling @ 8-900... Going to recheck the IAC again with the car acting more normal...
Only thing I'm still noticing is that when it gets fully warmed up it tends to chug when I get on it.
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12:15 PM
triker Member
Posts: 454 From: Yreka, Ca. USA Registered: Apr 2000
I had actually cleaned it once a while ago before the car was up and running, when we changed the gasket. But to be sure I sprayed it down again just the other night.
I'm going to seafoam the car tonight and see what that does. Also figured a bit of fuel injector cleaner would not be a bad thing either...Then go over it all one last time with TB cleaner to check for vacuum leaks.
Just noticed it developped an exhaust leak. nice ticking on the passenger side manifold. This should be fun!
