My car will seemingly randomly begin to rev upwards of 3000 rpm while at idle (manual transmission) after a brief period of driving. Shutting down the vehicle and quickly restarting corrects it at least for awhile. This has been an ongoing problem for over a year and I believe it is now happening more often and to a higher rpm. There is no check or service engine light coming on. My car has roughly 84,000 miles. Has anyone experienced this before? Any info. would be greatly appreciated. Thanks.
It won’t set a check engine light until it has idles for 2 min at 950 or higher. Then it will set a P0507. The culprit is the intake manifold gasket. It gets sucked in around the No 1 cylinder. You can verify this by squirting some type of carb cleaner, fuel injector cleaner or spray oil around the gasket at the no 1 cylinder. If the idle changes, then what ever you are squirting is getting sucked in.
This is a common problem with the SL. Use a felpro gasket instead of the oem, they seem to be stiffer. I’ve got over 200k miles on my SL, went through two oem gaskets, I’m now using the felpro and it seems to be working.
The problem might be with the Idle Air Control valve. This is what controls the engine idle speed and can malfunction where it goes to the wrong position for the idle condition. The IAC valve is located on the throttle body and looks like this http://www.autozone.com/autozone/catalog/parts/partsShelf.jsp?displayName=Idle+Air+Control+Valve¤tPage=1&categoryDisplayName=Engine+Management&navValue=15900207&itemId=207-0&parentId=59-0
Start the engine and while it’s idling take the handle of a screwdriver and tap on the IAC valve. If the idle speed changes when doing this, replace the IAC valve.
Thanks a lot for the info. I will definitely try this out.
Tester could be right IF the oem iac has been removed and replaced with an aftermarket one AND you are experiencing a sticky throttle. The egr comes into the manifold right behind the throttle plate so a sticky throttle is common in these. The oem iac has a shield to keep the gunk off the shaft of the iac, aftermarket ones do not.
The intake manifold gasket is still the bigger problem with these. There is no support around the no 1 cylinder on the head side and only three bolts in this area. The power steering pump blocked GM from putting a bolt on the upper outboard corner. (stud and nut but who’s counting)