1991 Teg LS, automatic, 100K miles.
I just changed the Timing belt and water pump and now it idles at 500 RPM. I tried unplugging the IAC and resetting the idle screw, but even with it COMPLETELY OUT of the car it still wont idle over 750. I then took off the IAC motor and carb-cleaned the hell out of it. I checked it with battery voltage and it moves full scale and clicks. Reinstalled IAC and cleaned the throttle body and Air bypass valve.
IAC is working. when i unplug it and re-plug it in the idle stays at 500 when I unplug it and then jumps to 800 breifly then returns to 500 rpm. all vacuum hoses are tight. WTF???

 

you sure the cams are in proper timing?

 

sounds like the cam timing is off and the engine isnt pulling enough vacuum

 

perhaps the cams are off. Actually it might be the exhaust cam because the intake cam drives the distributor and the timing is right where it was before i woked on it. How would I know if the exhaust cam is off a tooth? BTW it runs great above 3000 RPM. Pulls hard with lost of power and still gets 31 mpg on freeway. But it "bogs" below 3000. Should all 4 marks line up across on the cam sprockets at TDC??


[Modified by jetdriven, 8:50 PM 6/2/2002]

 

With the crank at TDC (the mark out by itself), the "UP" on the cam gears should be up and the marks on the teeth should point at each other and align with the mark on the back cover.

 

thats the problem, the back cover was warped from heat pretty badly. But it started up so well I thought I had them timed right. whats the stock vACUUM AT IDLE??

 

not enough fuel pressure

 

low vacuum at idle due to the exhaust cam retarded one tooth. lined up the cams per HELMS manual and it now runs perfect.

 

retarded, lol

 

hehe, I won that round.

Done it a few times on a SOHC motor.

 

only go helms on the cam belt change!! hgaynes did not mention driving 5.0MM pin punches into the cam caps or how to set cam belt tension!!