Weird Idle - No coast, car speeds up

[awehlage]

So normal idle on my car is about 700RPM.

Today I was driving and let off the gas to coast to a stop sign and the RPMs didn't drop and actually the car sped up. I was driving 25MPH and it sped up to 40MPH before I hit the brakes.

At the stop sign the RPMs were 1000RPM in drive. A little high. Threw it in neutral, tranny clunked and RPMs went to 1250.

Back into drive = 1000RPM. Tried it in Reverse and it was 750 RPM. Back into drive = 1000RPM. When I got home put it in Park and it was 1250RPM.

Thoughts? Tranny clunked only between drive and neutral and neutral to drive. No codes present.

[tigger]

Will your scan tool read TPS%?

Sticking IAC can cause high idle as well.

[awehlage]

Yes, I can get live throttle position %. Certain value I should be looking for? I can check FSM as well.

I cleaned the IAC tonight when I got home. It was definitely full of carbon buildup. Also checked the throttle body and cleaned it.

I have a spare TPS sensor and IAC from a JY throttle body I could swap out. I will see how the drive to/from work goes tomorrow.

[Paulaurora]

Had this issue on 3.5 2001 was bad TPS .

[awehlage]

Thanks Paul. Here is an update:

Started the car this morning to get to work; codes present upon startup were P0102, P0412, P0418, P0443.

I let the car idle in Park for 5 minutes before putting in drive. RPMs were between 800-1000. Put the car in drive an the RPMs stayed the same. Normal operating conditions the car would idle around 1200RPM upon a cold startup and then drop after a minute to 700RPM. This is some sort of warm-up phase the car always did!?! Not this morning.

Drove to work with no apparent issues besides CEL illuminated. Got to work, put the car in Park, engine idled at ~1200RPM. Cleared the codes before turning off the ignition.

Live data on my Dashcommand App was not working either. I couldn't get any information from the PCM concerning fuel system or emissions. The app said I was getting 524 MPG. No TPS, IAC, Torque, Horsepower, or Load %.

Dug in the FSM and it looks like IGN 1 circuit (both fused and relay) are the culprit with a short to ground. Swapped out the perfectly good 10A fuse on the IGN 1 spot with a new 10A fuse (fuse was not blown). Started the car, no CEL. Drove around for 15 minutes with one symptom: When I coast below 35MPH the RPMs flutter between 700 and 1000. About every 15 seconds the RPMs go from 700RPM to 1000RPM and then quickly back down to 700RPM.

Will try the JY TPS sensor.

[Paulaurora]

hmm I wonder y u got Purge Control Valve Circuit Malfunction code don't think its related but I had this code my self had to replace the sensor and few month later the plug. but 2nd air system code etc doesn't make any sense y they so random maybe issue with the power like short or something .

[awehlage]

All of those systems are on the IGN 1 circuit according to the FSM. I switched out the fuse for IGN 1, maybe it was a bad contact or something. I will go from there after I drive home 30 minutes tonight.

[Paulaurora]

oh I see nice to know.

[awehlage]

Well everything is back to normal for now. No codes, have driven hundreds of miles since yesterday morning at various MPH.

Just in case I cleaned up a JY TPS and IAC and have them stashed in my toolbox in the trunk.

[Paulaurora]

cool

[awehlage]

Yeah....just waiting for the next thing to happen. It's inevitable!