last week i changed rotor and cap,plug wires,fuel filter,water pump, and plugs. i now have developed a surging problem. when the car warms up the idle surges from 600 upto 12-1300 rpms and then drops back to 600. i have sprayed carb cleaner around the vacuum lines i could see and the idle didnt change. i also unplugged the maf and no change. the only thing that changed it was when i unplugged the iac valve when i did the idle helg around 1200rpm. the car runs super except for the idling problem. also the check engine light is off. i cant get it back to the mechanic untill thursday and would like to avoid going if I can. any help would be great
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remind me what yr and motor. what were the plugs gap'd at?

 

sorry 97 z 28 5.7 dont know the gap i didnt do the my mechanic did

 

why did he change only the cap and rotor and not the opti? its not a good idea. if your goin though all the crab to get to the opti your better off changing the whole thing. the price difference is not that much. unless its some cheap china crab, in that case it could be the cap and or rotor. if the water pump leaked on the opti or its old (60-100k) the chances are thats what it is. you can check the flash count on the iac with a noid light to see if its changing and if it is then the computer(ecm/ecu) is getting bad info from somewhere. 02 sensors, opti, map, mas or the ecm.

 

well he did say the iac was moving in and out with the idle changes. he put it on his computer real quick the day i brought it back.

 

one other question. what should the rpm's be if you unplug the aic

 

I first was thinking that the opti may have been crabbed up inside (the optical reader). But he said the engine starts to surge after it warms up.
A bad opti would make the engine run crabby cold or hot. Now I'm thinking a closed loop/sensor problem instead.

 

oh crab,,, i thought the ecu ran off the crank sensor on limp and cam sensor on closed. the idle would depend on where the iac valve is when its unplugged.

 

i wish this thing would just through a code and be done with it lol

 

The crank sensor on 96 & 97 LT1s is only used to detect misfires (OBDII requirement). Clocking signals to the PCM are still generated by the Opti.