Rep Power: 0

Just put the front end of the LX together. The cruise module was smashed, put a new one in, it works. When idling, car "surges" about .5K RPM, from 1K-1.5K, like somebody regularly pumping gas. Doesn't happen at speed or with A/C on. I've checked the Vac system, all looks good. Could there be a little one hidden somewhere I'm missing??? Car sat up for about a yr or so with smashed front. Thanks.

 
Rep Power: 266

What do you mean by "put together?" An automatic IAC valve on a 5-speed throttle body will cause it to behave like that.

 
Rep Power: 0

Ah, sorry, It was in a front-ender. Replaced the left front fender, both headlight assemblies, hood, and radiator support. Oddly, the airbags didn't deploy, but then agian bulk of impact was above the bumper-even re-used the grille. Didn't mess up radiator or anything else except the cruise module. It's an automatic 4cyl.

 
Rep Power: 266

It's hard to say. It could be an air leak, a dirty IAC valve, or even a leak in the radiator/hoses. I had the same problem because the previous owner somehow put a hole in the intake manifold metal coolant barb. I had it welded up. But I also cleaned my IAC valve and throttle body which also was a factor.

I would start by making sure you don't have coolant leaks. Run the car with the radiator cap off, heat and fans to max to get out any air trapped in the system. Then, put the cap on and see if it idles properly. If it didn't fix it, clean the IAC/throttle body. Don't touch the idle screw.

 
Rep Power: 0

Thanks, I'll give that a try. Don't think there is any coolant leaks as I've never noticed any spots under it in the driveway, even after idling for a while, and the system hasn't been fooled with.

 
Rep Power: 0

Changed the IAC (NOT cheap) but that did the trick. Had to adjust the idle a little, but no more surging...Thanks Clef!!