I cannot seem to determine what the high idle problem is with my ea82? The idle wants to shoot up to 2500-4000 and the only way I have been able to bring it down to at least 1500 is by pulling the idle air control valve hose out of the air intake boot. I've replaced the mass air flow sensor and oxygen sensor and also backed off both the idle speed and mixture screw on the throttle body. The timing is dead on at 20 BTDC.

Plug the idle control valve inlet and see what happens. Sounds to me like it's stuck.

I had that problem on my SPFI converted Brat for a bit. It would come and go. Turned out to be the wiring to the IAC.

The CTS can also cause weird varying idle including high rpm when it shouldn't. And no code. Also verify that the wiring is solid.

Plug the idle control valve inlet and see what happens. Sounds to me like it's stuck.

o.k. I'll try that today. I know there's plenty of vacuum there.

The CTS can also cause weird varying idle including high rpm when it shouldn't. And no code. Also verify that the wiring is solid.

A new CTS and a junkyard manifold harness is on my Christmas list for   Santa.

Plug the idle control valve inlet and see what happens. Sounds to me like it's stuck.

I did the plug trick after I got her warmed up. Much better runner now. No miss or hesitation when driving around town. Think I'll let it cool off and see if it's still going to have the cold start problem? I've had to feather the pedal to keep it running during a cold start until it warms up.

Edited December 19, 20169 yr by darsdoug

Plug the idle control valve inlet and see what happens. Sounds to me like it's stuck.

O.K. started it cold and it will actually idle when it's cold now.  Thank you!   

A couple weeks ago I'd removed the solenoid from the IACV and hooked 12 volts to it but never detected any movement. Did I fry it? When the IACV's are stuck open is it a major vacuum leak causing the oxygen sensor to over compensate resulting in a high idle?

12V won't fry it.  If it didn't react - click and move - it was already dead, or very stuck.

I'm educated guessing here - but if the IAC valve is open, I'd think it would raise idle.  Not a leak.  Its more like gas pedal part way down.  MAF senses more air flow, so ECU sends more fuel.  RPM goes up.

 

  A vacuum leak would lean out the mixture - I've only seen vacuum leaks make an engine run crummy, not increase RPM.

 

O2 sensor has no effect until the engine is up to normal operating temp.

I'm educated guessing here - but if the IAC valve is open, I'd think it would raise idle.  Not a leak.  Its more like gas pedal part way down.  MAF senses more air flow, so ECU sends more fuel.  RPM goes up.

 

  A vacuum leak would lean out the mixture - I've only seen vacuum leaks make an engine run crummy, not increase RPM.

 

O2 sensor has no effect until the engine is up to normal operating temp.

I'm starting to understand these pre-OBD II systems somewhat now. "Thank you again". So..... when the ECU gets a message that the engine is under load it opens the IACV accordingly and mine happens to be stuck open. And that would be the non-current position of the solenoid plunger correct? No volts/commands coming from ECU to the solenoid?

Edited December 21, 20169 yr by darsdoug

I found a thread that states you need to have an air gap of at least .028"  (at the idle stop screw)  or the ECU won't allow the engine to go into idle mode? So I tried it. Hey it worked! Cold start is 1200-1300 RPM and drops down to 600-800 RPM fairly quickly now. I told a friend about it and it fixed his high idle also. It was a post by Ivans Imports and states, "The throttle body hard stop must be set right or won't make idle contact in TPS and will not let ECU go into idle mode". I might still have to tweak it a bit because I can feel the throttle plate hanging up in the bore a little, but it sure has helped

Edited January 22, 20179 yr by darsdoug

You should not be playing w/the idle stop screw.

The idle contacts are adjusted by moving the TPS,not the idle stop screw.

 

Reset the idle stop by adjusting it so that the throttle plate has the minimium possible opening w/closed  without binding.

THEN adjust the TPS so that the idle contacts are closed w/a .012" gap and open w/a .031" gap.

 

An unmetered air leak is a common cause of a high idle too.

An unmetered air leak is a leak between the MAF and the throttle plate.

Edited January 22, 20179 yr by naru

o.k. got it.  Yes I had removed the TPS last month and had never marked it's original position. Playing with the idle screw wasn't very bright either.

I should get it corrected now though. Your input was vital to my understanding. (I'm still a novice at this) I've been dazed and confused with the adjustment sequence on this puppy for months.  Thanks Naru.

Yes. Worked like a charm.