High Idle when put in park

[jinx8402]

My car has been acting weird recently. Starting about 2/3 months ago, every once in a while when I put my car in park after driving 15-30 minutes, the RPMs will shoot up from 650/700 RPMs to usually 1500 RPMs. It does not happen all the time, though. I was not having any misfires, and the car ran smooth for the most part.

About a month ago I replaced my spark plugs, fuel filter and air filter. I also had ordered COPs but did not get them for another week or so. There was no oil leak, so I did not do the VCGs. The high idle was happening much less frequently than before. Then about 2 weeks ago I installed the new COPs. Again, everything while driving is smooth. No stutters and no misfires. But when I put the car into park it still shoots up to 1500 RPM what seems like once every 3 or 4 trips with my car.

Any ideas?

 

[glanga]

idle air control valve maybe needs cleaning or replacement. remove it and try using some non-chlorinated brake cleaner, worked for me with erratic idling

 

[jinx8402]

Thanks for the quick reply!

Is this easy to get to? Where is it located and/or do you have any pictures to show where it is.

Again, thanks for the quick reply and I will definitely look into cleaning it.

 

[glanga]

Might need a throttle body cleaning, could be as simple as that. The throttle body should be simple to find. I forget where exactly they are on the cars. Never had to do it to an LS.

 

[97stscaddy]

The throttle body is always at the engine end of the air intake hose.
The IAC motor is under the engine cover. Its a large can like object with an electrical connector on the end and a few vacuum hoses coming off of it. Its normally mounted to the side of the throttle body.

 

[jinx8402]

Cool thanks. I know what/where the TB is located. Still not positive on the IAC though. Looking at this picture:

is it the part just in front of the TB with the gold valve opening facing the front of the car?

Also, what should I use to clean both? What are the steps to clean them? and finally, what exactly am I cleaning (like what should I be cleaning)?

 

[JWerner2]

Check the air filter and MAF first. Those are the more simple things than work on to others. Also be careful with the TB its coated or something like that ( someone fill in ) and it can be damaged. Try some sea foam, maybe even a oil change.

Sea foam goes into the vacuum line and can also be added to the crank case before a oil change.

I find with funny idling that in most cases a simple oil+filter change stops it.

 

[2000LSMichael]

Yes, you are correct about your location about the IAC (has the gold piece where the tube connects to).

I believe that they require an 8mm socket if I remember. There is a small gasket behind there, so be careful taking it off if you don't have an extra.

When you take it off, you will see a small disc in the IAC that probably will have some black dust on it. Clean it with throttle body cleaner, but be sure the cleaner does not go toward the sensor end.

 

[jinx8402]

Thanks.

However, I feel extremely stupid...and kinda irked right now. I was going through my receipts last for my last oil change, and the place put in 7 qts of oil in my v8! I can't believe I didn't notice that at all. I have taken my car there since I bought it in July '06. I looked at every other receipt and they all only show 6 qts. So I called the shop, and the guy told me he was sorry it happened, and is giving me a free oil change next time I go. The reason I take my car to a shop for the oil is because I purchased an extended warranty when I bought the car for internal engine and transmission. This requires that I take the car to an ASE certified shop to perform oil changes.

So now that I know there is an extra quart of oil, I plan on draining a quart out. Does anyone know if there is a quick/easy way of doing this? Or would it be best to just replace all of the oil now? BTW..this coincides with the racing RPMs when I park, as I got the oil changed towards the end of March.

 

[JWerner2]

I cant explain an easy way to drain it but I would suggest asking them to do it or asking them for a change now and awarding the freebie later/next time you need a change.

 

[97stscaddy]

Don't just go draining oil out without checking the oil level first. The amount of oil that gets put in your engine is up to the person who does the change. If the tech who changed your oil did not feel that 6 quarts was sufficient, then it is conceivable that he added another half quart or so just to top it off. In which case the shop would charge you for a full quart. Besides that, one extra quart is not going to hurt your engine. If this were a transmission fluid change then there would be plenty of reason to worry, but in the engine there is no need to panic over one quart.

All throttle bodies are coated with a protective finish to prevent the bore from corroding. There are several companies that make cleaners specifically for the throttle body that will not harm the protective coating.

What you need to clean away is the buildup of carbon. It will look like soot. An old toothbrush will help to gently scrub away the buildup.

 

[JRiffe108]

Check oil level, if too much oil is present, request oil change place adjust oil level.

Overfilled oil pan will not cause high idle, reduced power if anything.

IAC (Idle Air Control) and TPS ( Throttle Position sensor) will cause ECM (Engine Control Module) to fluctuate idle.

If sensor is bad, it will send wrong signal to ECM which rasies idle. Remove intake hose from Throttle body and using CRC brand TB cleaner, spray short burst while engine is idling. Do not allow car to stall. Very short controlled bursts are all that is required. No scrubbing is necessary.

DO NOT USE Brake cleaner or any other claimed TB cleaner. CRC has the correct formula for the coated Butterfly and Chamber.

If cleaning does not correct the problem, then find technician who can hook-up diagnostics to verify signal from TPS / IAC.

 

[jinx8402]

Thanks everyone for the help.

I cleaned both the IAC valve and the Throttle body yesterday. I must say it runs soo much smoother now. The car feels much more responsive accelerating from a stop. Also, It has not idled high at stops/when the few times I have driven so far.

Thanks again!