​​​It's been doing this from the start as far as I'm concerned. Fixing many other things along the way doesnt seemed to have affected it's high idle.

 

I see you have measured the gap at the butterfly valve in the throttle body, and did not adjust. That is good. Could you remove the duct from the air filter housing off of the throttle body, start the engine and hold your hand over the top of the throttle body - but not the smaller intake of the IAC. Does the idle change? If it does not, then slowly/progressively block off the IAC intake and see if you can manually produce a lower idle. Another wild thought, you could disconnect the connector off of the A/C low pressure switch, which is on the dryer/accumulator to see if for some reason the ECU is bumping up idle for an A/C demand signal.

 

Yeah, I hear it's a big no-no to touch that screw, as it's purpose is not idle adjustment. I took the throttle body boot off, and put my hand over the the top of the throttle body. WOW it's got a lot of suction, I shouldn't be surprised. The engine will just about stall. If I cover the IAC cavity with my finger, and leave the throttle body bore unblocked, there's no change in the idle. I also tried disconnecting the A/C pressure switch and no change. With the throttle body boot off and the engine running, I also heard a hissing coming from the hole that goes to the idle bleed screw.

 

Yeah, I should have just said block off the throttle body, but it is hard to get a good seal. You got me with the air coming from the idle bleed, I had to go do what I was asking you to do myself. In your opinion is the suction down the throttle body through the butterfly valve or the idle bleed, it is almost impossible to separate the two, although you can plug the idle bleed fairly easily by itself. What I just experienced with mine. Very little suction across the top of the throttle body. Some suction down the idle bleed, but it is rather silent. Idle starts being affected with about half the IAC port blocked and the engine will begin to stall when 3/4 of the port is blocked. I think we are right where we were: There is air getting into your intake via a route that it shouldn't. There is also the possibility that the IAC is not functioning properly.

 

Alright, we may be getting somewhere, or at least confirming that air is coming in somewhere it shouldn't. The strong suction definitely was coming from the butterfly valve, again; it being VERY strong. Like a shop vac. Blocking the idle bleed hole lowered the idle a teensy bit, maybe 50RPM? Blocking the IAC passage made no difference and did not stall the vehicle. Have any routes in mind that the air may be taking? I'm also open to the idea of a wacky IAC, I'm pretty sure it's original.

Also, if you're asking about the hissing noise I heard, It was definitely coming from the idle bleed. As when I covered it, the hissing minimalized.

 

I didn't ask but did you block the idle bleed and the IAC port at the same time? It seems to me, based on the near no suction past my butterfly valve, that it is either hanging up on something, like a ridge of sediment, the linkage is somehow holding it slightly open, or it is out of adjustment. Have you tried pushing the linkage in the closed direction to see if there is any change in idle speed?

 

I did not try to plug the IAC and idle bleed ports at the same time, but I can try that tomorrow morning and will report back. I'm not sure what to think regarding it being hung up or having misadjusted linkage. The car starts up around 700RPM and climbs from there. I'd think that if the linkage was hung up, it would idle high at all times. I also have not tried pushing the linkage in the closed direction and will try that tomorrow as well. I'll keep the thread updated.

 

I missed that it idles right on a cold start (I see it now though). The fact that it is capable of idling correctly and then changes is unusual.

 

Ok. So I plugged both the IAC passage and Air Bleed hole at the same time when the engine was up to temp. Practically no difference in Idle speed. There is a small difference when plugging the Air Bleed hole, but it's probably only like 50RPM. Another thing I noticed, is that there's suction from the IAC passage when the engine is cold & around 700RPM, but once it is up to temp, there's no more suction. I presume that means the IAC is closed all the way?

 

So air starts to bypass the throttle body/IAC when the engine comes up to operating temperature... What is the vacuum hose off the EGR connected too?

 

The Vacuum hose off the EGR goes through the transducer and to the vacuum assembly (which is brand new), and through the assembly, it goes to the Vacuum output of the EGR solenoid.

 

What I was really asking was the source, but it doesn't matter, if the EGR was opening, it would be allowing exhaust gas into the intake, not combustable air.

 

Oh, sorry about that. The vacuum source of the solenoid goes to the vacuum harness, and from there, it goes into the intake. And yes, EGR is opening.

 

What the heck, what happens when you pull the vacuum hose off of the EGR solenoid on the inner fender by the ballast resistor?

 

If I pull the vacuum source off the solenoid when the engine is up to temp and running, the idle increases a small amount. Maybe 25-50RPM? not a big change. Can hear hissing from the line as well.