Over revving Saturn- is 4500 RPMs at an idle normal?

saturn
ls

#1

1989 Saturn 5 speed, 4 cyl, 185,000 miles. Just started overrevving, when I try to go into 1st or 2nd or idle RPMS jump to 4500. So not a good thing. Any help or predictions or advice? Do not tell me to buy a new car, not in the budget, or maybe it is. She has been with us since birth and has not had any problems - just routine maintence done as schedule suggests.


#2

It’s not normal to have an idle speed of 4,500 RPM’s. The problem might be with an Idle Air Control valve that’s gone whacky.

The IAC valve controls the engine idle speed anytime the accelerator is released by allowing air past the closed throttle plate. If the IAC valve allows too much air into the engine the O2 sensor detects this extra air and then commands the computer to add more fuel to compensate for the extra air. This then causes the idle speed to go too high.

Locate the IAC valve, and the next time the idle speed goes too high, take the handle of a screwdriver and rap on the IAC valve. If doing this has an effect on the idle speed replace the IAC valve.

Tester


#3

Has anyone at least looked to make sure that the throttle isn’t binding? You’d not necessarily be worried about the pedal, but the plate itself at the throttle body. This is probably a very simple issue such as that or the IAC as Tester mentioned. Its certainly not a car killing issue.


#4

Double check the model year on this car. I believe the first year for any Saturn was 1991 or 1992. Tester and cigroller offered two likely suspects. I would check those two items in that order. To add to cigroller’s suggestion, a frayed throttle cable could very well cause this issue. I have an older car that recently had high idle issues caused by a frayed throttle cable. My only other suggestion is to check for a possible vacuum leak. I have seen several Saturns with blown intake manifold gaskets, and that will cause a high idle on these cars. These gasket issues have been seen on either of the 1.9L four cylinders in the SL/SC car lines in my experience.


#5

Is your car a '99, not '89?

Are you saying that if you’re sitting at a stoplight and not doing anything the engine is running at 4500 rpm? If so you have a stuck or binding throttle cable or plate, or a massive vacuum leak. Or when you try to accelerate in 1st or 2nd gear the rpms go to 4500 before the car starts to move appreciably? That would indicate a clutch problem.

The Idle Air Control Valve is almost certainly NOT the problem. It can only raise engine speed to 1800-2000 rpm on that car, and that’s wide open.


#6

I apologize…it is a 99.

Thank you all for your help…


#7

The SL1 model has a history with intake manifold gaskets around the #1 intake port. As far as I know, the SL2 (twin cam) engine does not share this issue.