Interesting idle problem

[elwesso]

This is strange... When I start my car in the morning, and it gets up to normal temp, everything is all good (idles PERFECT).. But if I start the car when it is warm, it idles at about 550..

Scenerio (and applicible): I drive home from school, it gets up to operating temperature... Then i go inside to get my stuff, and put my golf clubs in the trunk, and then head out.. When I start the car, it idles at 550 or so, but then when I get to the course (about 2 miles away) it idles perfect again...

Its kind of like the idle is in a loop, meaning it starts at 1250, then down to 550, then back up to 700 (or whatever perfect is)

EDIT: It has done this as long as I can remember, but I figured i would post when everything has been done.....

[Q45tech]

Idle speed is a function of coolant temperature and time since starting. When ever it reaches 176F [actually at 160F] the speed is dropped to the preprogrammed level........IF the ecu can maintain speed by the normal amount of IAC duty cycle and ignition advance. Dirty TB and IAC or misadjusted IAC may allow lower than normal speed when warm AS A SIGNAL TO YOU to get things cleaned up or set properly!

[elwesso]

My IAC, TB and plenum are all sparkling???

So could this mean that hte car is running a touch too hot???

[Q45tech]

Sparkling? What is the IAC duty cycle in neutral warmed up [10-15% [max] and in drive - no ac on [18-20%]......then AC on [28-35%].

Correct idle speed is 650 +- 50 rpm as read on a Consult not tach.I like 675 +- 5 rpm in neutral warm no load.

[elwesso]

Obviously without going to a dealer I dont have any way of knowing these things....

My car needs to go in soon for the 10 year airbag inspection sometime and Ill go ahead and have them look at this too...

[Q45tech]

Ha! Air bag inspection.........they rot after 10-15 years and need replacing........luckily they fail softly in a puff of confetti that can't hurt or help you.........actually they do help some, even very old ones.

Isn't it nice they are only covered for 7 years

[maxnix]

Damn, another myth busted!

[Q45tech]

Just pull out your trusty analog oscilloscope and look at the IAC duty cycle.

Measure the on time vs the off time = duty cycle.

I don't expect DIY to have a Consult but they must have a decent Digital VOM with min-max hold < $50 on ebay HD-160] and some kind of oscilloscope [it can be 40 years old if it works], plus fuel pressure gauge ----even a homemade one [$20-40] and a vacuum gauge from Sears [$15].

Otherwise you are at the mercy of a dealer with a Consult.

[psychic_mechanic]

At least know can tell my wife I have a reason to buy the next Gov't surplus oscilloscope I see. She doesn't dig the "I always wanted one" line.

-Vinny

[Q45tech]

http://www.picotech.com/auto/automotive ... 2_100.html

or a big old clunky analog unit from EBAY: Tek 2225 oscilliscope $150.

http://cgi.ebay.com/ws/eBayISA...25412h ... SA...25412