3.8 high idle 3K

Topic: 3.8 high idle 3K (Read 1046 times) previous topic - next topic

3.8 high idle 3K

September 29, 2009, 09:45:59 PM

yep new to here...

yep searched then got lazy after half an hour

Ok so it mostly wants to sit at 3 grand in n or p about 1.5 grand when in gear, suspect tps or that ice thing ontop of the throtlebody. I dont have much exp with the injected stuff, im used to 70's pickups.

also sometimes it will "stumble" back to normal-ish, no its not downshifting, it will do it in first gear (selected) , so the problem intermittantly goes away, verry briefly mostly at light throtle. When i let her eat she takes off normal, it just wont idle where its supposed to.

it is now giving me the "light" so i will get a calibrated paperclip to get the code which i need to find copys of.... gona try google but if any one has the list a copy would of course be welcomed. and which pins on the connector do i jump.

Thanks

3.8 high idle 3K

Reply #1 – September 30, 2009, 12:18:51 AM

possible vacuum leak?

3.8 high idle 3K

Reply #2 – September 30, 2009, 05:28:01 PM

We had thought of that bit didnt figure it would do that much... of course Im more used to carbs... we sprayed carb cleaner everywhere (to find a leak) but no results there, gonna try more this weekend when I get home.

3.8 high idle 3K

Reply #3 – September 30, 2009, 09:33:19 PM

How does it act when you first start it up cold? That would tell you whether or not a vacuum leak is to blame (for the most part). The oxygen sensors, that would compensate for a vacuum leak, aren't on immediately. I would think that with that high of rpm's though, the car wouldn't run at all when cold if it were a vacuum leak only. The car will only run that high it if has the airflow to let it run that high (not as much needed outside of drive though). A bad sensor would not cause this behavior. Perhaps messed up idle air bypass valve? Cap off any vacuum lines you can and listen around for whistling sounds. You can also try spraying carb cleaner (bogs down) or starting fluid (a rough idle would smooth out and/or rev up a little) around gaskets and hoses to see if you can find a place that makes the engine react, other than the intake tube.

We could shoot in the dark all day without some diagnostic codes or seeing it in person though.

3.8 high idle 3K

Reply #4 – September 30, 2009, 09:41:05 PM

I believe TCCOA.com would be a little more helpful for you.

3.8 high idle 3K

Reply #5 – September 30, 2009, 10:07:07 PM

3 questions

how long have you had this car(assuming the one in your sig)?
have you cleaned the throttle body, and have you ever messed with the throttle screw and cable?
does it shut right down when you turn the key off?

3.8 high idle 3K

Reply #6 – September 30, 2009, 11:48:09 PM

Just got car, from friend, started doing this after taken off the road for paint. I can take it to his shop and he will pull codes we just haven't had time ( I'm on the road). I was hopeing this may be a common enough sympome. It does this instantly ( 3 grand idle speed) and constantly,(occationally it acts as if it sputters but is just dropping to a more normal idle maby 1 to 1.5 grand if drifting or light throtle. Heavy throtle seams normal. Uppon Shut off it runs for a few ( like 2 or 3) seconds and that is followed by a low pich wine. not like and engin "Deseiling" though, it runs smooth for those few seconds.

3.8 high idle 3K

Reply #7 – September 30, 2009, 11:50:54 PM

And throttle cable can move freely through its intended range, I have not cleaned it, dunno if he did.

3.8 high idle 3K

Reply #8 – October 15, 2009, 12:48:16 AM

ok it was the iac (idle air control) i still have a bit of a stumble occationaly but it now idles where it should, ill get her there!!!

3.8 high idle 3K

Reply #9 – October 15, 2009, 01:45:35 AM

Was it stuck open, causing a vacuum leak?

3.8 high idle 3K

Reply #10 – October 15, 2009, 10:12:21 PM

Quote from: Seek;294877

Was it stuck open, causing a vacuum leak?

Unlike those with MFI (multiport fuel injection) the IAC on our 3.8's or the 5.0 with TBI (Throttle Body Injection) does nothing more than push the throttle open. It's strictly a linear actuator that pushes on the throttle linkage to control the idle. It can't cause any vacuum leak. Easy to see when it's causing the fast idle. It should normallly pull back after the engine's hot at idle, leaving a small gap between the rod and the throttle linkage.

If it ain't pulling back something's hinky with the signals seen by the ECM to let it know that the engine is warm and idling below 700 RPM. One of my two 86's is doing the same thing. I just haven't had time to work on it, and would probably need scuba gear to do so lately.