1988 Mighty Max Won't Smog (High Idle)

[Mightymax]

Hey guys I recently bought a 1988 Mitsubishi Mighty Max for pretty cheap, I just needed to smog it. Sadly, it was labeled as a gross polluter so now I have to go through the referee (California). During my first appointment he told me that the truck had an engine swap (he was guessing a 1991 was put in) and that I needed to time the truck and lower the idle speed before I brought it back. The idle speed just won't come down.

The idle screw is backed completely out, not even touching at this point.
The accelerator cable has slack in it, and won't turn any farther back. When you apply pressure to the accelerator plate/pulley thing backwards the idle does drop, however it hits a plunger that won't allow it to turn back farther?

Does anyone know what this plunger thing is, or how to adjust it or the idle speed? Sorry I don't know all of the proper terms to describe the problem.

[pennyman1]

It sounds like you have a throttle solenoid for the A/c that is holding the throttle above idle - you can unbolt that out of the way to see if that lets the idle drop. If it doesn't, post some pics so we can see what is going on. BTW if its a carb motor, the newest it can be is 1989 - that is the last year for carbed motors. There is a member on here also who is a carb referee, he may be able to help you get the truck to pass, since he knows our trucks - do a search for referee.

[geezer101]

Another option is that somebody has messed with the Mikuni's base settings and adjusted the fast idle screw on the throttle linkage. Some guys when they run into issues with the Mikuni, they just keep turning screws until it does 'something'. Trying to undo someone else's brilliant work then turns into a major PITA. The fast idle adjust screw is located on the inside of throttle cable linkage under the shaft (it's the screw that has a spring sandwiched inside of it) - try winding it out and see if the idle backs off.

[Mightymax]

Thanks for the input! It turns out that the Idle Speed Control System needed to be readjusted. The plunger on the idle speed control servo wasn't retracting far enough to bring the idle speed down to where it needed to be.