Hello

My Camaro has a very high idle speed... it's between 1400 and 1700 rpms. At the moment there's a lot of other more important things to do on the car but I have to get through the vehicle inspection. They do a full braking there and with such a high idle the car pushes against the brake. This might be a reason to not be able to pass the inspection.

I think it's some kind of a leak on the intake manifold because I checked the vacuum system already and also the iac.

Is there a way to temporarily and artificially reduce this idle speed even without fixing the problem so that I'll pass the inspection?

Thanks,
Thomas

 

What year, and engine? You might be able to lower idle speed with the minimum air screw. But you're probably on to something with a vacuum leak, and it might be a simple fix, I'd look into that before rigging something together.

 

Hi

It's an '88 Camaro, TBI, Vin E.

I've already checked the vacuum lines. My intake manifold is leaking, I think this could be the reason. When I start the car, idle is about 2500 rpms. Only when I put the car in a gear it's around 1500 rpms. When I put it in neutral it's again around 2000 rpms, so it's quite bad.

I'm not sure if you're suggestion works because of the manifold intake leakage. I thought maybe there's another option that might keep the rpms low.

 

No - because the system meters air based on manifold pressure. Leaks = lower pressure = more fuel. Only way to bring down the idle is to fix the leaks.

GD

 

Throttle body gasket leaking. Very common on TBI engines (cars and trucks). Spray around TBI with air cleaner on. If idle changes (not getting any spray in idle passage or EGR area) most likely TBI gasket, while TBI is off clean passages underneath unit. (around PCV hose area)
Joe

 

for the $$ involved not worth f#####g around - just fix it

 

When looking at vacuum leaks, don't forget the brake booster. It can make a big leak. Pinch the hose off with pliers and see if the idle drops. How did you check the IAC? They can be tough to verify. One method you can use is to perform the minimum idle air adjust procedure, where you jump terminals A&B of the ALDL. Then disconnect the IAC, turn the key off, and remove the IAC and see if the pintle is extended. I think on the TBI you can even look down into the passage from the top of the TB and see the pintle.

While I see IAC failures now and then, I have also seen the IAC coil drivers in the ECM fail. You really need a labscope to test the drivers. There is also an IAC tester made by Thexton Tools, though it's probably discontinued long ago. We have one here that is nice for testing the IAC itself to be sure it operates normally and that the engine can achieve and maintain normal idle.

 

Just block air feed to IAC with a rag, way back there was plastic plug to put in the feed. Most common is TBI gasket. Basically unmetered air flow. Check PCV valve also, most after market rattle at idle or leak to much vacuum. PCV valve is a factory calculated vacuum leak. To much leak ='s high idle on injected motors.
Joe