92 Idle problems

Hi I have a 92 L series with 155K+ miles and have an idle problem. When it is cold it sometimes revs really high 2k+. When it finally slows down ~ 5 to 10 seconds, the idle stumbles (i.e. almost stalls, revs up, slows down, repeat...) When I get going (> 2k RPMs) it runs alot better... I have replaced the plugs, wires, and engine mounts, and it helped but did not fix the issue. I am going to change the PCV again, but don't expect that to fix it. Any ideas?

Any codes on the engine computer? Get to Josh's page for the procedure:

http://www.surrealmirage.com/subaru/subaru.html

Click on 'notes and tips' then on 'engine related'. Not all codes trip the check engine light.

Not sure the order of importance, but look into:

IAC, Idle Air Controller. This gizmo needs to be checked out for operation and additionally needs a good cleaning. You'll need a manual for this. The Haynes will do, or get a subscription to www.alldatadiy.com .

intake ductwork; any breaks or opening between the air flow meter and the intake manifold will make it idle funny. The rubber boots may have cracked and will need to be repaired (cloth & rubber cement).

vacuum gauge. any vacuum leaks in the intake manifold?

Let us know what you find.

Nick

Ok, did some more work on the car...
Cleared all the codes and none came back. Ran a can of seafoam through the pcv and found exhaust leaks in the driver side y pipe, and the seals in the junction. Ran a compression check and 1 was a little lower than the rest, but within norm. It idled better cold this morning (stable at 1k RPM), but now stalls and dies when braking :banghead:
Any ideas?

Oh yeah, after clearing the codes, the seat belt light is flashing.

Dude, WTF?

You did some work on the car, but did you really do anything that addressed the problem with the idle? No codes on the ECU is working in the right direction. Seafoaming, then replacing the PCV and replacing the motor mounts is busy work.

Have you put some Seafoam through the IAC or checked out how it is operating?

Nick

Gee does your 92 have the original motor and transmission mounts? Never mind don't really care, and by the way I also changed the shocks and struts too, just more busy work. However unlikely, I thought I would include it in recent work on the vehicle.

Anyways, no I haven't put seefoam through the IAC, but am looking into borrowing the tools to be a vacuum system check. I'll let you know how that goes.

An update for anyone who may have a similar issue. Check your timing it appears that the whole issue was the timing had jumped by one tooth.