Idle problem
 

I've been having some problems with my car's idle. Whenever I come to a stop, I put the car in nuetral and coast up to the light with the brake on. The engine will rev up to about 2K RPM then back down to 1k, then back up to 2k. It does this 3 or 4 times before it stops and idles right. It also seems to hesitate a little bit at about 4k RPM when I am accelerating. I thought it might have been the plugs or wires, but I changed them and it still does it. I'm kinda leaning towards a faulty TPS, but not for sure.

Kinda sounds like a TPS problem to me.

Or your idle motor.

I would get a autometer and test the voltage on both and see if its with spec defineed by HMA.

If the car is rolling, this is normal. The ECU sees that the vehicle is still rolling, and keeps the idle up high to prepare the engine/tranny for you putting it back into gear 'at a roll'. Once you come to a complete stop, it should idle back down to normal.

if the idle is jumping around after the car is stopped, then yeah, something's going wrong there.

My car will hover at 2k rpms while coasting as well.

I had a problem where it would surge from 2k sometimes up to 2600 while coasting. And it would idle at 1500rpm. Drove me f****** nuts, until one day I was swapping out a bad fuel and found the oil had caused the PVC breather hose to expand and cause a vacuum leak. I guess the fuel hose I used was not impervious to oil? I wouldn't be surprised since these same "high pressure" fuel hoses had dry rotted to the threads in only 2 years or so.

Well, it starts doing that right before I come to a stop, then does it a couple more times after I've come to a stop. It doesn't happen all the time, but enough to make me worry. Sometimes the idle even drops down to about 400 or 500 when I'm stopped, almost dying then back up to normal. How would I go about testing the TPS and the idle motor? I've got a multimeter at the house, would that work?

random, that's good to know why the tranny does that. i thought there was a problem with mine because when i'm coasting to a stop after i take it out of gear and the rpms drop, they drop only to about +-1300, then settle once i'm at a stop. i was eventually going to post about it.

Robert-

The procedure for testing the TPS (with a multimeter) is up on HMAservice (webtech). If you can't find it, drop me an email and I'll email it to ya.

Random, I found the testing procedure on HMA. I just got done testing it, but I don't know if I did it exactly right. The TPS measured according to specs, except for the voltage on it, didn't really know if I was supposed to test it with the connector disconnected or not. The resistance was reading right around 2 ohms. The connector part gave me some way off readings. I tested the power supply voltage from the connector to the TPS and it was only showing 78mV. Could that be the problem, or was I just not doing something right?

The voltage at the connector should be 5V. The voltage coming OUT of the TPS should vary between .5V and 4.7V depending on throttle position. You have to probe the signal wire and ground wire to get the signal voltage.

I'm wondering if you tested the signal connector and ground rather than the 5V line and ground.

Random, I'm really not for sure which ones I tested. I tried to follow the diagrams on HMA but the connector didn't have the numbers printed on it like the harness on the TPS did. I haven't been back home yet to test it again, but I will this weekend. It's still been idling erratically when coming to a stop, sometimes back and forth between 1K and 2K RPMS, and sometimes it'll idle down to 300 or 400. Is there anyting else I should check while I'm under the hood? I've recently changed the plugs and wires and PCV valve, so those should be alright. I also had to replace my front O2 sensor, which stopped it from running so rich, and fixed the hesitation problems I was having.