97 bonneville, high idle!

[freelancewriter]

I have a 97 Bonneville SE with 117k, and am having a problem that I don't see elsewhere in the forum.

When I start my car, it idles up to, and stays at, 3,000 rpm.

When I put it in drive, it idles around 1500 rpm with my foot on the break. (It's necessary to hold the break to keep the car from moving.)

Take my foot off the break, and off it goes. It will reach around 60 mph and 2,000 rpm without my foot on the gas.

I live in a cold climate (Wisconsin) and it is winter. The problem persists unless the car warms up AND I turn it off and restart it. Then it runs fine. (Not sure if this is 100% true, as I haven't repeatedly tested this.) The three times that I've parked it in a heated garage, it has run fine, as well, though it was only parked in a heated garage for a few hours after being thoroughly warmed up from driving.

The code reader showed a TPS problem. (I don't remember the exact code - it may have been 201???)

I changed the TPS, and even voltage tested it. The voltage range is .475 to 4.5. That seems acceptable - not sure.

I also changed the O2 sensor. (At 117k, I figured it was due for a change, anyhow.)

I don't see any obvious vacuum leak problems.

(I can't imagine any connection, but a few months prior to these problems I changed the PCV, fuel filter and air filter after having the car die on the interstate. It ran fine for at least a month after that.)

Any suggestions? I don't want to randomly replace sensors when I really have no idea what the problem is, and the computer is giving me no code other than a TPS problem.

[sam g.]

check your idle air control sensar it controls the engine vacum.

[Flatrater]

Actually an idle control motor controls the amount of air entering the intake at closed throttle. A dirty IAC can cause idle problem but most of the time it would cause an unstable idle. It sounds like you have a vaccum leak when the engine is cold and the temp increase causes the engine to expand sealing the leak. If you take some carb cleaner spray the engine area in small areas and see if the idle changes. When the idle changes that would indicate where your vaccum leak is.

[freelancewriter]

Thanks, Flatrater. That seems logical, and will be a fairly simple test.