97 tacoma vibration

[Karen]

I have a 97 tacoma 4 cylinder, automatic. When you are setting at a light after the engine is warm the motor vibrating shakes the steering wheel and hood. If you give it a little gas it quits vibrating. It has been tuned up and throttle body cleaned and still the same. Mechanic says the computer controls idle speed and cant be adjusted. This doesnt seem to be a miss but vibration at very low r.p.m. How do you fix this?
Thank you.

[way2old]

First of all, welcome to our little forum. If it is a vibration and not an engine miss, have the motor mounts checked. If they are weak this can cause the shaking.
It could still be an engine miss due to low fuel pressures also. Just guessing here and trying to give you some places to look. Let us know what you find. Maybe Dand or Venturi will drop by. They have more experience than I do on Asian vehicles.

[DanD]

Your mechanic is right that the computer controls RPM and that there is no specific idle adjustment for it, but there are a lot of other things that will affect idle quality.
Ignition timing may be off and it is adjustable, dirty fuel injectors, excessive carbon build up in the combustion chamber.
You said that it was tune up, so by rights the timing should have been checked and adjusted (if needed), but it may be worth asking him if it was. It’s not very often that the timing will change and maybe it was overlooked.
As for the dirty injectors have them professionally cleaned, don’t waste your money on the bottle of stuff you can buy at the corner gas station. I’m sorry but I think most of them are crap and don’t do anything other then make people feel as though they have done some good by adding it to their tank.
There are actual machines that can be hooked to the fuel system that have concentrated cleaners in them that’ll do a good job of cleaning. Plus they will decarbonize the engine at the same time.
Even if the cleaning doesn’t solve the problem it sure wouldn’t hurt anything by having them cleaned.
Dan.