Okay all, I have a problem. I have a 90 Vert that I bought at the beginning of the summer as a daily driver. The original 13B blew, so I bought a parts car (a 91 vert, identical to mine but ragged out) that had a factory re-man Mazda motor installed in it that was supposed to have about 10k miles on it. The motor was installed in it by Mazda techs, and worked perfectly in that car (until the car was stolen and wrecked). We pulled it out and put in my vert, hooked everything up correctly and it runs like a champ. That was my summer project, and I've driven it daily since then, working out a few kinks along the way (coolant leak, battery issues, blah blah) but a persisting problem is the idle. When I start it cold, it goes to the quick-warm up cycle, and that's all well and good. It idles at about 2,000 RPM cold (too high, I know) but as soon as it begins to warm up (the needle gets off of C and begins to climb) the idle will become erratic. It will drop to 1,500 and surge constantly to about 1,700 an then fall. Rise. Fall. Rise. Fall. Until it gets fully warmed up, then it will drop to 850-900ish like it's supposed to, and have no issues. The surging only stops when the AC compressor kicks on, and then the idle stays firmly at 1,500. As soon as the compressor kicks off, though, the surging starts up again. Anybody have any ideas? Maybe bad grounds? TPS? Vacuum leak? It runs and starts and drives perfectly normal, minus the idle issue. I'm on winter break for about a month and I need to sort this out before I go back to school. Any info or tips would be immensely appreciated. Thanks, everyone.

 

Green/Red TPS wire set at 1 volt w/key to on and engine "completely warmed up."

 

Hmm...I'll do that first. Thanks.

 

Any luck? Did you find a solution? I'm having the same weird idle issue where it'll surge when warmed up, then when the A/C is turned on the idle climbs and stays steady.

 

Hey man, sorry for the delayed response, I've been bogged for a while. Yes, I got it fixed. My fan clutch was bad. $50 and it's good as new. Surged once since then, just had to readjust the TPS to 1k and it was good to go. Runs better than ever. Good luck man!