Throttle body cleaning

[TechGizmo]

After cleaning the throttle body on my 93 J30 I notice an increase in idle RPMs from 700-800 now 1000RPM even after the engine has reached operating temp. It drives good otherwise but I am wondering will the RPM go back down after a while?ThanksTerry

[elwesso]

This is somewhat common........ You could always adjust the IAC to lower the RPMs......

The RPMs may or may not go down..... My idle is kinda goofy..... it starts out at about 1250 rpm, and then goes down to 750 when warmed, and then up to like 850 when it is fully warmed........

[sultan]

my idle also went up after cleaning the TB. it was about 800 in drive, drove like that for awhile, then got the IACV adjusted to bring it down to 650-675 in drive, free of course, with a consult-like device telling me exact numbers. a consult (or consult like device, hehe) is really good because you don't have to guess what the rpm is off your tach.

[TechGizmo]

Thanks for the reply guys, but what is IAC(Idle air control) and where is it located on a 93 J30?

[Q451990]

IAC (or AAC as it's called in the service manual) is a valve that's controled by the ECU and puts more air into the intake on the engine side of the throttle body. The ECU uses this to maintain idle when you turn the A/C on, use the power steering, etc.

I'm not sure of the exact location, but it'll be mounted to the plenum or intake manifold, and should have a two-pin electrical connector and a set screw. In many cases, people will set the base idle up to compensate for a dirty throttle body - after it's cleaned, the idle will be higer than spec. until the AAC valve is set back to normal.

Heath

[TechGizmo]

That is making sence to me because the throttle body was very dirty. I used an old tooth brush to reach inside and scrub the backside of the butterfly and the amount of carbon that came out was incredible.

I was hoping that the RPMs would settledown after all the bad stuff burned off, but after two days of driving it still stays at 1000RPM, so I think I will have to adjust the IAC screw to bring the idle down to 750-780RPM.

[TechGizmo]

Well I adjusted the idle screw today on the IACV unit to lower the idle RPM from 1000 to 800RPMs, it took two complete CW rotation of the screw to get there, however I want to lower it even further to say 700-750RPM.

What do you guys think, what is an optimum idle speed for a 93 J30?Thanks

[elwesso]

800 is probably about right...... Because you dont want it to vibrate when you put it in drive with the brake on.......

[mateo]

Thanks for posting the threads. I plan on doing this soon myself. Never have done anything like this before.