Hi everyone,

I have a 1985 245 DL that I just purchased and I can't get it to pass CA smog. I am and auto upholsterer and know little about the mechanicals of an engine. I'm having idling issues, it seems to be running high, as i'm am told. My car does not have a tachometer, is there any other way to check my engine's RPMs? I have checked for vacuum leaks thoroughly and I have also cleaned the PCV, throttle body, checked for TPS alignment clicks, have the black idle speed screw in as much as I can turn by hand, closed off one of the idle air control valve and the engine wants to stall. Also I ran power to the idle air control valve and it does open and shut.

I've read some were that the engine should should rev up then rev back down shifting from drive to park, mine does not do this. When my car is in park the engine stays in the higher rev range and does not rev back down. I have also disconnected the idle air control plug started the car up and it sounds the same with it plugged in. Is this a problem?

Could there be a problem with my TB TPS? I have already checked for alignment issues and listened for the clicks. Does the TPS have anything to do with the IAC? Does the A/C effect idle? If so how do I check that it's not running? When I turn off the car I can hear pressure releasing behind the dash.

What else should I be looking for?

Thanks in advance,

David