91 4 Runner 3.0 manual trans 4x4. It is idling at 500 rpms and seems to be missing. If i bring it up to 800 it smoothes out and runs great. Do I just turn in the idle screw or is there something else that could cause this?

 

If the idle screw was set where it was from the factory and you have a low idle, then adjusting it to raise the idle again won't fix the actual problem. It won't hurt anything by doing it, but it won't fix it. The idle may not even remain higher after adjusting it in some cases.

There are a number of things that can cause a low idle. It just depends on knowing what the exact symptoms are before you can begin troubleshooting.

This is the '93 factory service manual for 4cyl and 6cyl engines. Favorite place it...
http://personal.utulsa.edu/~nathan-b...fsm/index.html

You'll see under "Engine-Mechanical" a number of sections. Click on the troubleshooting guide and read under "low idle" for your symptoms and possible causes.

 

Ok the service manual doesnt make sense as far as the chart for trouble shooting. I am just going to start testing everything I guess. I will start at the AFM and end at the o2 sensor. I dont know what else to do I know it isnt exactly a scientific way of doing things but at least it will all be checked.

 

it should run at 800 rpms, check your sparks.

 

i m also having problems, i just replaced my knock sensor and then adjusted my timing, it just isnt adding up. i cant get the unit to adjust more than +/-10 and its still running rough. and i did recently replace my plugs/wires. any help?

 

I have tested everything and everything seems good the idle is up a little (not sure how or why) to about 700 and it seems a bit smoother. One odd thing i found was that there was no idle air control valve that I could see. I believe it is mounted next to the throttle position sensor. There is what looks like a factory block off plate.? If anybody knows if this is something that is normal or something that is a patch please help.

 

ok been really busy lately but still need some help with this. It seems to be runnig good but i can not figure out why there is no Idle Air Control Valve. PLEASE HELP!!!!