[iNeedHelp3000gt]

1992 3000GT SL (Stock)

So I've had an idle problem for awhile now, but it has gotten much worse. I have a video of how the car acts if anyone cares to see. It acts different each time, but most recently it starts around 2000, rises to 2500, then dips back to 2000 and repeats itself. Sometimes it just starts idling at 2500 and slowly hovers around the 2000-3000 range. It is also a very rich idle and does not have any vacuum leaks to my knowledge, which makes sense that it runs rich.

Things I've Adjusted:
TPS
SAS
BISS (I didn't know not to touch it atm, plus it was already touched by previous owner, and on top of that it couldn't make a 3000 rpm idle any worse)
ECU Coolant Sender (Tested by shorting male harness)
Throttle Cable (Cleaned TB as well)

Things I've Replaced: (Listed fuel related items too just incase)
Crankshaft Position Sensor
MFI Relay
MAF Sensor
Oxygen Sensor (Used Bosch 13812, is there any issue with this? I for sure thought replacing the o2 sensor would do it)
ECU
TPS
IAC

I've also tried leaving the battery disconnected for a day. Another thing I did was try to run it without the ABS module plugged in as I read if your anti-lock light is on it could cause a high idle, and unplugging it would normalize the idle if it is the problem.

I've done just about everything other than check the FIAV.

Is there anyway to diagnose a bad FIAV?
And is there anyway to manually close it without taking apart the throttle body? Or will I need to take it apart and create a bypass plate or buy a new TB/have it rebuilt.
Is the Bosch o2 sensor okay to use?
What else could cause extremely high idle?

I was attempting to datalog it but there seems to be little help on the internet for 1g ecus.

Any and all advice/questions are appreciated.
Thank you in advance, and Happy New Year!

 

[yevgenievich]

I made a bypass gasket. There is a plug on a side that can be knocked out. Behind the plug is where the FIAV assembly screws in. But it is set very tight and on two assemblies that I have, I could not get it to turn in. Theoretically tightening the assembly will close the passage around the wax ball. Have you tried manually setting the IAC valve to fully extended position and run the car with it unplugged? That will let you know if you have other sources of air leaking in causing high idle.

 

[iNeedHelp3000gt]

I made a bypass gasket. There is a plug on a side that can be knocked out. Behind the plug is where the FIAV assembly screws in. But it is set very tight and on two assemblies that I have, I could not get it to turn in. Theoretically tightening the assembly will close the passage around the wax ball. Have you tried manually setting the IAC valve to fully extended position and run the car with it unplugged? That will let you know if you have other sources of air leaking in causing high idle.

How would I go about setting the IAC to fully extend? I was going to try and figure that out but I tested the coils and they were good so I didn't bother but I'd still give it a try.
And about the FIAV I saw a video of a guy popping that plug off and closing it on one of the other DSMs. I myself could not find the plug without taking the TB off, but I may be blind. Which side is the plug on?
Thanks for the reply btw.

 

[yevgenievich]

The fiav plug is on the back of the fiav block.(essentially under the intake if throttle body is installed). On IAC, if you take off the solenoid part(the three screws) then can manually rotate the shaft of the pintle to either screw it in(closed) or out(open air passage).

 

[iNeedHelp3000gt]

The fiav plug is on the back of the fiav block.(essentially under the intake if throttle body is installed). On IAC, if you take off the solenoid part(the three screws) then can manually rotate the shaft of the pintle to either screw it in(closed) or out(open air passage).

Okay thanks, I'll try it out. I'll probably have to just bite the bullet and take the TB off later too, even though I've had much more difficult tasks with this car, I just don't have the energy right now lol.

 

[iNeedHelp3000gt]

The fiav plug is on the back of the fiav block.(essentially under the intake if throttle body is installed). On IAC, if you take off the solenoid part(the three screws) then can manually rotate the shaft of the pintle to either screw it in(closed) or out(open air passage).

Got it!!!! It was FIAV. It really wasn't all that bad. Just made my own bypass real quick to test it out before I do anything professional looking. I ran into other problems along the way. My power wire gave out right when I went to test it out so I had to take care of that first. This car is one thing after another haha.