how do you adjust idle speed?

[hungt1999]

I used to have a 1987 Camry, there was a small port covered with a rubber cap that you open to turn a little screw inside to adjust the idle speed.

Is-there such a thing on the Corolla? I don't want to play with the throttle body and cable to adjust the idle speed if I can avoid it.

My current idle speed is around 650 RPM (manual transmission, 1.6L) and the car vibrates quite a bit at that speed which is quite annoying at a stop light. If I increase the engine speed to around 700-750 with my gas pedal, all vibrations miraculously go away ! therefore, I am considering increasing the idle permanently to 700 RPM for comfort

[kevmac]

Usually there is a throttle adjustment screw near the throttle body (where the intake hose ends at the engine). It will adjust the throttle cable tension. I have not adjusted the corolla so I don't know exactly on this car. I would not look to fix your issue this way though. Sounds like you may have bad mounts to replace that will only get worse and could cause drive train problems if not dealt with soon. Think of engine vibes as similar to body pain telling you to see a doctor before it's too late.

Start with the passenger mount and go from there.

[hungt1999]

Originally Posted by kevmac

Usually there is a throttle adjustment screw near the throttle body (where the intake hose ends at the engine). It will adjust the throttle cable tension. I have not adjusted the corolla so I don't know exactly on this car. I would not look to fix your issue this way though. Sounds like you may have bad mounts to replace that will only get worse and could cause drive train problems if not dealt with soon. Think of engine vibes as similar to body pain telling you to see a doctor before it's too late.

Start with the passenger mount and go from there.

ya you are problably right, I need new engine mounts as indicated also by my problem of engine jerking if I release the gas pedal during acceleration with the car in gear

I heard the rear mount is really painful to replace. As for the other front, right and left mounts, they should be easy right? is-it just a matter of lifting the engine from underneath by placing a jack and wood block under the oil pan to relieve the weight and all those mounts should be easy to replace?

[cipher93]

On these cars I'm almost positive the idle is non adjustable. The idle is regulated by an idle air control valve/motor because at idle the throttle plate SHOULD be closed. this motor bypasses that to allow for it to idle correctly. If it is not functioning correctly however, your idle will not work well. There is a way to test it that I don't recall at the moment but I'm sure someone else knows because this is a fairly common issue.

That is my guess if the idle is too low. the other are worn/wet plug wires, distributor cap/rotor and plugs.

EDIT: Btw, what makes you think your issue is motor mount related still? Motor mounts would be a constant vibration.

[hungt1999]

Originally Posted by CJRocker

EDIT: Btw, what makes you think your issue is motor mount related still? Motor mounts would be a constant vibration.

You got me thinking there. By increasing the engine speed to 750-800RPM using the gas pedal, all vibration went away... if it were the motor mounts, will the vibration occur at all speed?

I was thinking motor mounts because I have also a problem with the car jerking if the gas pedal is suddenly release during acceleration and still in gear. Some people had suggested it could be cause by worned out mounts.

[cipher93]

Originally Posted by hungt1999

You got me thinking there. By increasing the engine speed to 750-800RPM using the gas pedal, all vibration went away... if it were the motor mounts, will the vibration occur at all speed?

I was thinking motor mounts because I have also a problem with the car jerking if the gas pedal is suddenly release during acceleration and still in gear. Some people had suggested it could be cause by worned out mounts.

Yeah, that sounds like IAC issue.

Motor mounts would actually get worse at higher RPMs. As mentioned in your other thread, the jerk could be the transmission getting worn. That said, my 3 speed auto corolla does it, and the motor mounts are fine.

[hungt1999]

Originally Posted by CJRocker

Yeah, that sounds like IAC issue.

Motor mounts would actually get worse at higher RPMs. As mentioned in your other thread, the jerk could be the transmission getting worn. That said, my 3 speed auto corolla does it, and the motor mounts are fine.

what is IAC? how do I check that?

[ganda1f]

IAC is the Idle Air Control valve. Two things can be done to check it.
With the engine warmed up, bridge the E1 and TE1 terminals in the diagnostic connector in the engine bay. Idle RPM should increase to 1000-1200 RPM for like five seconds and then go back to normal. If it does, the IAC is fine. Otherwise measure the resistance of the IAC valve. Measure across the middle terminal and each of the two outer terminals. It should be 19-23 Ohms.

The IAC valve is a dark green plastic piece under the lever where throttle cable is attached. It is roughly two by two inches.

[kevmac]

The vibrations are probably resonance. Raise your engine pan on the passenger's side a bit with a board under the jack in order to take support away from the mount. Repeat your vibe test. I don't need any other proof. And yes they can cause vibes at idle and do. You can change one mount at a time. The rear mount can be done last (even next year if you want).

check the idle thing too. People are always asking about this issue especially in the winter with cold starts.