Marc Gelefsky

The idle on my 3.6 seems a little rough, The tach is rock steady but it just seems a tad rougher, Like the old passenger seat is moving a little more
Would a cleaning of the MAF be in order?
Otherwise car feels great!

BruceP

Mine had a lumpy idle when I first bought it, and now it doesn't. I can't pinpoint what fixed it, but here's what I did over the first couple of service visits:

- New fuel filter.
- Throttle body service.
- Motorvac the fuel system.
- New plugs.

Runs like a champ.

ls911

How many miles when you did this?

I got that going on as well. Runs like dream but seems to bounce just a little bit at idle

I got 13K so I was not even thinking plugs, filter, etc...

Maybe I am being just to critical, I am somewhat of a perfectionist

BruceP

It had about 76,000 km on it... 47,000 miles or so. It had seen about 7,000 miles a year of daily-driver-type usage.

Loren

Most of the time what you describe is a dirty throttle body.
The MAF does nothing at idle (unless it is shorted).

ls911

Ok

I am not going to sweat it, for now...

Thanks BruceP

AndyK

Try cleaning the throttle body - smoothed out my idle nicely. Although these cars normally are a little rough - as you know!

DFC

Throttle body clean is quick and cheap, I'd start there.

http://www.renntech.org/forums/index...howtopic=15413
http://euroautoforums.com/forums/ind...showtopic=1351
http://www.popularmechanics.com/how_...e/1272341.html

Macster

and there was no dirt on the thing. (Cleaning was an attempt to rectify a hunting idle and other symptoms that ultimately proved to be due to a failing AOS and not a dirty/bad MAF.)

I've got nearly 80,000 miles on the current MAF in my car and haven't had it out to clean it once. Running stock air intake and filter too.

For some model year vehicles, a variable cam timing selenoid could fail and the symptom was a lumpy idle. Don't know what your car's year is, if it has the electric variable cam timing selenoid, but if it does, and if MAF cleaning or other potential solutions don't help...

Sincerely,

Macster.

Pugnacious P

macster, what years had the electric variable cam thing? I have had a idle issue in past. I cleaned the MAF, ICV and throttle body with some small success, but still feel vibration intermittently. My next thing was to replace fuel filter at next oil change, but perhaps that cam thing is issue. What kind of cash is the repair?

manny_g

the variable cam timing solenoid failure is normaly the contributing factor on later cars..

Benjamin Choi

isn't this vibration thing considered normal?

what's tough to gauge here is we're trying to prescribe something to something where we don't have any quantitative figures, just subjective observations about a seat moving more than usual.

then people read this and they're like oh man my seats vibrating, i need to go do x and y as i read on rennlist... what i notice is, the seat sometimes vibrates more, sometimes it doesn't vibrate at all. depends on temp, cold start or strip mall visit, etc.

i'm not so sure we're going to come to any sort of logical, salient conclusion here. if the vibration makes your voice sound like you're talking into a whirring fan... then consider a real looksy.

Tippy

What monitors engine idle and regulates idle airflow?

I remember that when I placed a screwdriver on the butterfly in the throttle body (2000) I could feel the butterfly constantly moving back and forth. What tells the butterfly how much to open for idle?

On the 99's, the idle control valve or idle air bypass valve directed air around the butterfly, what tells the ICV or IABV to open or close at idle?

Loren

From the Tech Book (for egas cars):

"The throttle position is determined via a potentiometer fitted at the throttle valve. The DME control unit supplies the potentiometer with a regulated voltage (5 V). Depending on the potentiometer position (throttle opening angle), a higher or lower drop in voltage occurs at the potentiometer. The DME control unit uses the voltage drop and the corresponding current flow to determine the smallest opening angle for the throttle. This angle is defined as the idle speed position."

Doug Donsbach

The DME is monitoring engine RPMs and adjusting air intake (either with the stepper motor throttle or the ICV in the case of the mechanical throttle) in order to maintain the idle RPM setting.