How can I raise the idle on my 90 Corolla the screw is all the way adjusted

I have a little vibration from the motor mounts which disappears with an extra soft touch on the gas pedal at idle. If I would keep the car I would change the mounts, but there are a lot of new parts already ($2,200 worth, with labor)…I cleaned inside the plenum…(I think it’s called) thanks…Mike

Throttle body and plate too (throttle plate?)

Idle speed is closely related to ignition timing. Is ignition timing on this car set manually, or is it computer controlled? Advanced timing raises idling speed, and retarding timing decreases idle speed. If you are at the max adjustment, I wonder if your timing is correct?

I’m pretty sure that by 1990 these went to fuel injection (yes?) which means that you don’t adjust the idle - the computer does it. There is often a stop screw somewhere on the throttle body but it is best not to mess with those at all. Instead you do all the normal stuff to make the car run right - like plugs & wires & filters and stuff. Of course, no one would know what to suggest because we only know there has been $2200 worth of mystery work, and nothing else.

Those screws are not supposed to be touched except in very limited circumstances and only by someone who really knows what’s going on with the car.

Vibration at idle could be due to any one of a number of things, from minor to major. The major would be if compression is down on a cylinder or two so a compression test is always Step One.

yes, of course…the work was by the previous owner (2 gas station bills $1500- rotors,calipers, tires, etc and $500 timing belt) so no ignition work that i know of. I’ve had it 1 1/2 yrs to practice driving with my 2 girls. it has only 100k and runs clean and strong. That 1600 cc engine is plenty for the small car. Now I remember, I bought the $130 Toyota cap and wire set (one piece) which seemed awful dear…and I did change plugs and all filters (except fuel)…My new but unused timing light… I never got to use( one of my wife’s cleaning binges …and yes it it fuel injected… thanks, Mike

There SHOULD be a screw under a rubber plug on the fuel injection intake…most toyota’s have this…the Camry did…it was right on top of the intake plenum under a rubber plug…OUT creates more vacuum leakage and thus higher idle…in stops the vacuum leakage and lowers idle…you don’t have this flat head screw under a rubber plug anywhere? Its a pretty big plug/screw Usually very near the throttle body but on top of the intake plenum somewhere…its fairly obvious

That screw is to keep the throttle plate from damaging the throttle body when closed suddenly. It is not an idle adjustment. The computer is supposed to control the idle, but if the screw is adjusted out too far, the TPS wont know your foot is off the gas.

You might want to check the valve lash.