89 Corolla idle issues - Toyota Nation Forum : Toyota Car and Truck Forums

***79Corona*** · 03-06-2009, 10:33 AM

It has the carbed engine, 4AF? There is a bad dieseling problem, due to fast idling. Is there any reason I shouldn't assume that adjusting the idle screw will solve the problem?

90 GP · 03-06-2009, 06:24 PM

Check to make sure that the choke is opening all the way when warmed up, If it is binding clean linkage /butterfly valve with carb cleaner. Another problem is the throttle positioner on the carb which is a dual vac unit . If you get a hole in either attaching vac line you can get the advanced idle speed. The throttle positioner is on left side of carb when facing front of the engine.Check the other vac lines for possible leaks as well.

***79Corona*** · 03-09-2009, 11:21 AM

Is that the left side facing the front of the carb (float bowl glass)? Remember it's a transverse engine.

90 GP · 03-09-2009, 02:57 PM

The throttle positioner is on the same side as the float bowl sight glass.

90 GP · 03-09-2009, 03:01 PM

Here is a link on how to check out throttle positioner.

http://www.autozone.com/addVehicleId...00c1528006f1cc

***79Corona*** · 03-09-2009, 08:11 PM

Thanks, I probably have to take the air cleaner off so I can see everything. My daughter had to get back to school so I didn't have time to really look at it. I know the idle adjustment screw was not really working properly.

Donald · 03-10-2009, 08:11 PM

I would check the timing also, just to be sure.