: Weird RPM increase?



gtm245
05-28-04, 01:10 PM
I know this probably has nothing to do with oil lubrication at all but I thought I'd throw this out there as I'm stumped on what it is. Ever since I bought my car a few months ago the car has idled at exactly 850 RPM when in P or N and idled at exactly 750 RPM when in gear. About a week ago I got up in the morning and went outside to start my car. Ever since that morning it has idled at 1400 RPM in P or N and idled at about 1000 - 1050 in gear. Is there any good explaination for this? Do I need a good tune-up like plugs, wires, ect... or is it something else? I just have no idea why my idle all of a sudden went up like 600 RPM. :hmm:

The car is a good ole 96 Chrysler LHS with the 3.5L 24V V6. Hope this helps in some way. Oh and it has 153,000 miles on it. :rolleyes:

S10xGN
05-28-04, 04:51 PM
Sounds like a vacuum leak. You probably lost a vacuum hose (rotted or blown off).

gtm245
05-28-04, 07:56 PM
Wouldn't a vacuum leak cause a surge when you put it in gear? Like the car wants to race off without you touching the gas?

Dead Sled
05-28-04, 11:45 PM
clean the throttle body that will help

although a drity throttle body will cause low idle and stalling


err too many years ago since i was a chrysler tech

Stoneage_Caddy
05-29-04, 12:12 PM
saw similar issues in SR20 cars , there was a idle air conrtoll valve that would get plugged up or go bad . perhaps the 3.5 has a idle air valve somewhere ?

S10xGN
05-29-04, 12:48 PM
Wouldn't a vacuum leak cause a surge when you put it in gear? Like the car wants to race off without you touching the gas?

Why would it? I'd never seen that happen before...

If the problem occured suddenly like he stated, I'm still banking on a vacuum hose. I've had throttle bodies and IAC motors get dirty before and have never seen a "sudden" problematic change.

gtm245
05-29-04, 05:56 PM
Well it turned out to be the upper intake manifold gasket was leaking and letting in air. I put on a new Fel-Pro gasket today and all is well again. :thumbsup:

Dead Sled
05-29-04, 06:03 PM
glad to see you fixed it, I should have known better