High idle problem

[ICPREY]

I have a 95vr4 with an AEM EMS/wideband and MAP sensor. The car has started idling at around 1900-2000rpm. No Vacum leaks that I know of (boost controller indicates -21).I've changed the IAC with a brand new one. Also tried just disconnecting it...didn't help. I've swaped the the EMS and throttle body with another car that idled fine (same set up). If I put my hand over the holes on the bottom of the throttle body while its running the idle will go back to normal. As soon as I remove my hand it jumps up again. Any ideas?

[RL7]

The throttle body is leaking. It should be air tight.

[ICPREY]

I believe the slots on the bottom of the throttle body should allow some air out to regulate idle, just not as much as I'm getting...I checked it with the y pipe off since I don't need it on because I have a MAP sensor (Car will run/idle fine with no intercooler piping attached). Gonna troubleshoot it some more tomorrow.

[Fakepower]

I am not 100% certain but I dont think you should have any loss of air post MAS .... try those holes with starter fluid to see if you get a rev, otherwise im inclined to go with RL7

[ICPREY]

It doesn't have a MAS... It has a MAP. If I block the holes completely the car dies.

[ICPREY]

The coolant lines to the throttle body were switched between the rear turbo and inlet/outlet portion of the throttle body. It wasn't allowing the coolant to reach the IAC motor housing.

[KeithMac]

You sould not have any air leaking in/out of the throttlebody, the bypass for the IAC and FIAV are internal. Can`t think what "slots" you are talking about?.

[ICPREY]

If you look at the throttle body with the "y" pipe or intercooler pipe off it has 2 slots infront of the rotating blade. Guys who run a MAF sensor will not be able to gauge the amount of air coming out of the slots because the ECU will sence a vacume leak. MAP sensor guys it doesn't matter. I did fix the problem by switching the coolant hoses.

[J. Fast]

So it was the FIAV/coolant temp sensor not seeing warmup? I bet it was sucking down fuel since it never reached temp :). Nice work!

[ICPREY]

Yea instead of having a feed/return line for the coolant I had 2 feed lines. My wideband stayed at 12.5-13.5, but it just wouldn't idle below 1900.

[RL7]

Oh, you were doing those diagnostics with the y-pipe off. That makes a lot more sense now. Both of those slots bypass the throttle plate. One is for the iac and the other the fiav. Without coolant, the wax ball would never melt to close the fiav side so you basically always had the throttle partially open. You can block off the fiav side with a plate or something like that if you don't want to deal with the tbe hoses. You do lose automatic high idle at startup though.

[MaxClass]

Oh, you were doing those diagnostics with the y-pipe off. That makes a lot more sense now. Both of those slots bypass the throttle plate. One is for the iac and the other the fiav. Without coolant, the wax ball would never melt to close the fiav side so you basically always had the throttle partially open. You can block off the fiav side with a plate or something like that if you don't want to deal with the tbe hoses. You do lose automatic high idle at startup though.

OK, you lost me here.

What is "fiav"?

This is first I've ever heard about a "wax ball"? Is that something only women in the Army can attend?

Seriously though, a little explanation may be helpful to everyone else here. I have heard many time that disconnection the coolant flow from the TB would cause you problems but never knew the underlying cause or reason.

[RL7]

OK, you lost me here.

What is "fiav"?

This is first I've ever heard about a "wax ball"? Is that something only women in the Army can attend?

Seriously though, a little explanation may be helpful to everyone else here. I have heard many time that disconnection the coolant flow from the TB would cause you problems but never knew the underlying cause or reason.

The FIAV is the fast idle air valve. It is there to make your car idle higher when the car is first started. This is the part of the tb that the coolant flows to. It is in the same housing as the IAC. There is a ball of wax that expands as it is heated by the coolant. This causes the valve to close much like the stepper motor closes the valve in the IAC. The wax is mostly enclosed, but cleaning the throttle body with harsh solvents can screw up this wax and cause problems.

[Roybatty]

The wax is mostly enclosed, but cleaning the throttle body with harsh solvents can screw up this wax and cause problems.

Could this cause a low idle problem during open loop (i.e. engine cold)? Solution would be a new TB?

[RL7]

Could this cause a low idle problem during open loop (i.e. engine cold)? Solution would be a new TB?

It's possible. The ISC, FIAV, and idle setting all "work together" to get idle right. If one is screwed up, the ISC will try to compensate and all sorts of idle problems may result. If I suspected the FIAV was bad, I would remove the lower portion of the tb, fill the fiav ports with jb weld, and delete it. The FIAV is nice to have but it's not critical at all and it makes the engine bay more complex. I've deleted mine and I just use the gas pedal to run the car at 1 - 1.5 k for a minute when it's cold. You probably don't have to do that, but I warm up all my vehicles a bit before heading off.