It was overheating due to a leaking head gasket. I replaced that and it now idles at 3K. I've tried testing all of the EGR components and everything checks out OK. I don't have a timing light and couldn't check that, but would off timing make it idle fast??

Any help/advice would be greatly appreciated!!

 

Is the throttle arm resting on the throttle stop, meaning is the throttle closed?

Check for leaking vacuum hoses including the large vacuum hose to power brake booster.

The IAC valve on the throttle body controls idle speed. Is the valve connected to the wiring harness along with the coolant hoses?

 

Thanks for responding!

The circular throttle actuator is closed all the way to the stop when it's running.

I've been looking for cracked hoses everywhere, and can't find any. I will check again...

I actually took the IAC off and energized it. It opens and closes when I apply a 9 volt battery to the appropriate pins. The 2 coolant hoses are connected as well as the one that goes to the head. All connectors are in place. I cleaned it since I had it out and it moves easier now when I energize it.

Funny thing, after I cleaned the IAC, I put it all back together and now it's idling at 4K!

I tried putting it in N and starting it - same thing. The engine light does NOT come on. That means there is no error code, right?

 

The computer checks if idle speed is varying too much from target speed. Typically these checks are a predetermined test where the item being tested must fail over at least 2 driving trips. Perhaps the computer has not finished testing.

Check the IAC valve motor resistance. Disconnect the electrical plug and check the ohm reading between the top and bottom pins. Should be 17.0-24.5K ohm cold, 21.5-28.5K ohm hot.

Disconnect the battery cable for a few minutes in an attempt to reset the computer.

Note: If the car has a radio with security code theft prevention and a code set it would need to entered before the radio would work again. The face of the radio would have on this feature like theft protected, etc.

Since the engine idled OK before the work suggest for now limiting investigation to issues that could have been caused by taking the engine apart.

The engine may not have distributor and if so there is no method to adjust timing.

The computer sets the idle speed thus don't adjust the throttle stop in an attempt to lower the idle as this setting is factory set!

The throttle body near the throttle stop has a vacuum powered dash pot-throttle opener (looks like a small flat can) having a vacuum line attached. This device keeps the throttle slightly open when the engine is off (no vacuum). The throttle opener has a button that pushes against the throttle pulley when engine off to slightly open the throttle. This button should be fully retracted (pulled in by vacuum) when the engine is running. The tang on the throttle pulley now resting on the throttle stop.

Don't know if the engine would even run with a miss adjusted timing belt but you might double check this.

Air in the coolant lines of the IAC valve can cause idling issues. The valve also uses coolant temp to adjust idle.

A few other things to check. The idle will increase when the AC compressor is on (radiator fans will also turn on). Determine if the idle is increasing even more when AC compressor is working as an indication the valve is responding to computer inputs.

Check PCV valve system and any large vacuum hose. For power brake booster try removing hose at engine and plugging the engine port. Make sure the vacuum hoses at the throttle body are connected in the right order.

 

IAC resistance checks OK. The pot-throttle opener is behaving as you described. I didn't adjust the throttle stop, figuring this was probably not the problem since, as you mentioned, it was idling OK before the work.

I figured that the closed system would hold a vacuum, so I took put plastic wrap around the air intake and zip tied it into place to seal that. Then I took off the hose going to the power brake system and replaced it with a test hose at the manifold. I then thought I should be able to blow into the hose and sequentially blocked off or plugged ports on the manifold until I got resistance, meaning the system was air (and therefore, vacuum) tight. It wouldn't seal up. I got a long peice of tubing I could fit into my ear and listened around the mating surfaces of everything I worked on. I found a pretty large air leak around one of the fuel injectors. I am reseating that today to see if it clears the problem.

I've never heard of a fuel injector air leak causing high idle, but what the heck!

Have you ever heard of high idle due to fuel a injector sucking air?

Norm

 

Hey Joey,

The leak was at the fuel injector. I found a bent insulator and changed it out. She's running great now.

Norm

 

Great job in diagnosing the problem!

Thanks for posting back with the fix.

Enjoy your now fixed car.