this thing is driving me nuts.2000 SI, bone stock just CAI, idles at about 1500. steady then dips down really quick and back up about every minute. sorta wants to stall and jerks hard on take off,
things ive tried & checked: checked for vacum leak. check TPS voltage, adjusted valvles,cleaned IACV,
when the car is warm and i unplug the IACV the idle drops to normal.

any suggestions?

 

check for leaks again. have you replace a manifold gasket recently? the parts shop up here gave me the wrong one once and it didnt seal. so i did everything you have mentioned and finally found that it was the gasket. you can also look to see if its a bad iacv by jumping connectors down by the ecu with a paper clip if the valve clicks then its good. good luck.

 

jump which connector ? the same one used to set timing. so if its bad it wont click?

 

just checked for vac. leaks again, and there isnt any, i noticed that the idle screw had been tamper with. so i unpluged the iacv and tired to adjust the idle, and i wont go lower than 1200 rpm,?????? i turned the screw in as much as i could and i wont go any further. i think this TB is toast!!

 

Warm the engine up. Pull off the air intake to expose the throttle body. Put your finger over the lower port inside the throttle body. If the idle speed does not drop, then you probably have a vacuum leak. If the idle speed does drop, then you may need to replace the IACV.

You also might want to test for a malfunctioning ECT sensor under the distributor.

 

nothing happens when i cover that hole in the TB,no rpm change. i doesnt make sence, what your say , when covering that hole something has to be wrong either way, its either the rpm drops or it doesnt either way theres a problem, so what does it do when theres nothing wrong?
how can i test the ECT

 

The "when there is nothing wrong" scenario does not apply in your case. The ECU is throwing P0505, and your idle speed is high and fluctuating. Therefore there is a problem, and those tests help to pinpoint it. The test result suggests that you should carefully reexamine the possibility of an intake air (throttle body or IM gasket leak) or a vacuum hose/connection leak.

ECT circuit tests:

 

AHHHH i fixed it. but im a little embaressed to say it was the little hose thats in back of the IM for the crusie control, i sprayed and sprayed carb cleaner on the intake gasket, TB ,till today i found that little port,

 

ok NOT fixed completely, this car still keeps throwing this code, now what it does, when the like CEL comes on.

the car idles at 1500 rpm, when i put my foot on the gas, the RPM will bounce up and down really fast til it gets past 2000 rpm.

i have a little code reader that i use to clear the code but once it clears and read it again and it picks up the code within a mintue(CEL light doesnt come on right away through)
SOMEBODY HELP this thing is driving me nuts, just when i think i fix it, it comes on again

 

I just replaced my PCV valve on my ls swap. Seems to have fixed it.

 

what was your car doing same symtoms?

 

Another thing i noticed, it starts throwing the code only when it reaches normal operating temp....then the CEL will come after a few minutes of idleing

 

If you cover the IACV port in the throttle body with your finger and the idle speed does not change, then you still have a vacuum or intake air leak.

 

could that also mean the IACV is bad, i noticed that someone installed a thick plastic intake mainfold gasket but ive sprayed it with carb cleaner and idle doesnt change.

 

For what its worth, I was parked the other day and the engine light came on, along with the TCS light. The a/c slowly became warmer and idle failed to increase to compensate; it remained steady at about 500 rpm. After turning the car off and on again the TCS light went out but the engine light remained on. OBDII check showed the P0505 code. Simply unplugging and reconnecting the electrical harness on the ICV fixed the problem and I cleared the code using a handheld OBDII comp. I'll post again if it comes back or anything related pops up.

 

my idle does that too and its pissing me off. im always reseting ecu and only at idle will the CEL come on and then when driving its very jerky

 

well i havent had that car for a good while now, but it was a vaccum leak. the TB wouldnt snap shut all the way, making it raise the idle and the IACV would try to correct it,