I have a problem with my idle. Some background: I was having surging and hesitation, so I had my mechanic put a new throttle actuator in. It ran great for a few days, cruise control worked again, then it started to have problems again. The problem is different this time. The idle is too high. In Park or Neutral, the car will rev between 1300-1800 RPMs. In Gear, the car will rev between 900-1200 RPMs. The high idle causes the car to practically drive itself; in stop and go traffic, I constantly must ride the brake or the car will accelerate up to 30mph or so on its own. Also when this occured, the cruise control would not work at all. It started as an intermittant problem, but now it seems to be occuring all the time.

All signs pointed to a faulty throttle actuator. I had my mechanic replace the throttle acutator with a new one. Same thing happened. His handheld scanner idicated that the throttle valve (or something like that) was open when idling, when it should be closed. Any ideas would be greatly appreciated. We're having problems figuring out what is going on. I'm thinking something is faulty with wiring or even the computer unit itself.

On a side note, I failed my emissions, and nothing obvious is wrong with the engine. Mechanic is leaning towards replacing the cat. I had the cat replaced a year and a half ago just before I bought the car, but it is a non original part. My mechanic says it is a piece of junk (the cat). Could the throttle problem be linked with emissions? I hate to put a new cat on if it won't solve the problem.

Thanks,

Matt
94 E320 158k