high idle prob

SICKANDTWYSTED · #1 (**permalink**) 01-08-09, 11:20 PM

my 02 dts has started idling too high, when i start it up it idles at 1200 then after about 30 secs jumps up to 1800 and stays there until it warms ups after driving then it drops to 1200 again. once and a while it will idle at 800 like normal but seems to always go back to 1200. so any ideas.. i dont have any codes and i cleaned the tb it snaps shut nicely is there an idle control module that could be bad?

**Ranger** · #2 (**permalink**) 01-08-09, 11:28 PM

One word. PLENUM. Do a search. I've explained it so many times it should pop up on the first page.

93DevilleUSMC · #3 (**permalink**) 01-08-09, 11:32 PM

There's an Idle Speed Control motor that could be out. Another culprit could be a dirty throttle body and/or fuel filter.

**Ranger** · #4 (**permalink**) 01-08-09, 11:48 PM

There is no ISC motor on an '02. The '02 uses an IAC valve to control the idle. I think they used the ISC motor to about '95 or '96.

93DevilleUSMC · #5 (**permalink**) 01-08-09, 11:50 PM

Sorry, I got him confused with another guy.

**Ranger** · #6 (**permalink**) 01-09-09, 12:02 AM

Been there done that.

93DevilleUSMC · #7 (**permalink**) 01-09-09, 05:50 AM

Got the t-shirt?

**Ranger** · #8 (**permalink**) 01-09-09, 05:29 PM

Nope.

SICKANDTWYSTED · #9 (**permalink**) 01-12-09, 07:48 PM

ok cleaned the tb checked for leaks on the plenum and made sure the throttle is closing all the way but so far i haven't found anything. the car starts at 1200 rpm then about 20 secs later revs up on it own to 1800-1900 rpm and stays there. in drive with your foot on the brake its still at 900 and is pulling hard. from a stop it accelerates on its own and once and awhile after a restart when its warm it will idle normally until u drive around a again. could the idle control valve be at fault or is it working fine and i have something else telling the engine rev up? any help is appreciated.

**Ranger** · #10 (**permalink**) 01-12-09, 08:00 PM

I suppose the IAC valve could be at fault. It IS what controls the idle, but then again, it gets it's commands from the PCM which gives those commands on other sensor information. Try pulling the IAC valve and cleaning it. I'm sure there is a procedure for testing it in the FSM.

SICKANDTWYSTED · #11 (**permalink**) 01-16-09, 12:10 AM

i took that idle control thing out tried to clean it but it wasnt dirty. however i couldnt get the plunger on it to move with my hand, is that normal? here is a pic of what it looks like.

now the car is idling at like 400rpm sometimes also. its idling so slow that the lights dim and its gets close to stalling and the engine surges up and down. then the next time u start the car its back to the too high idle again sometimes 1400 sometimes 1800. any help on testing this would be appreciated i dont have a fsm

**Ranger** · #12 (**permalink**) 01-16-09, 12:32 AM

I'm not sure how you test the IAC valve, but I'm guessing that it is bad.

msturdiv · #13 (**permalink**) 02-26-09, 10:26 AM

My 01 Deville is doing the same thing. I cleaned the Idle Control Valve and that has helped so far. I looked at replacing it, but at $250.00 a pop, I am now looking for a suitable substitute part. Any ideas? Anyone.

SICKANDTWYSTED · #14 (**permalink**) 02-27-09, 12:15 AM

i ended up getting that part from rock auto and it fixed my problem.

99Classillac · #15 (**permalink**) 02-28-09, 10:14 PM

Hey Sick, is your car still running good? I have a high idle and it gets high, 3k rpm. I took it out and cleaned it today. It was dirty as hell and I cleaned it up real nice and I cleaned the TB and the cavity the IAC valve sits in. Worked for a day. I am wondering if it permanently fixed your problem. I don't wanna buy that valve if it won't fix my problem. But me and you had the same exact symptoms and if its working out for you I guess I'll try it too.