Originally Posted by ch@0s
Can an IAC valve act as a vacuum leak if it is not working correctly?
I have had my TPI apart 5 times now looking for a vacuum leak.
I have replaced every hose and connector. I have tried the carb cleaner method. I even smoked a whole pack of cigarettes and blew them in the plenum looking for it. When I run Datamaster my IAC counts are in the 100s. I have done the adjustment procedure but they did not go down much. The car runs and idles ok but it hesitates on acceleration. According to Datamaster its running very rich BLMs in the 108 range and at idle it hits 80 KPA .
Regardless of working correctly or not, because it allows air in through a port aside from the throttle blade, it is, and can be regarded as a vac leak.
At operating temp. 100+ cts means the t.blade is too closed and won't allow the IAC to compensate properly (160 is max. cts. and in cold start only). Depending on idle rpm would depend on cts. that you should be seeing. If
at approx. 850rpm on a modded motor, counts need to around 40 (a stock motor and idle rpm would be around 10-20 cts.). You will need to reset min air by turning screw clockwise which opens the blade and lowers counts. (unlike the book, w/data master running, turn min air screw *start w/a 1/2 turn, turn car off and restart the car, which will reset iac then see were you're at w/datamaster and proceed from there) this will also improve your off idle hesitation. The above needs to be done in closed loop at normal operating temp.
108 blm means pig rich, the ecm cannot, and will not comp. 108 period.....it needs tuning. Too big of an inj w/out tuning, cam changes, huge fuel pressure etc. etc. would be the usual causes when modding.
There is no way you should be seeing 80 kpa at idle even with a huge cam. 80kpa means low vac. at idle and with smaller aftermarket cams it should be around 40-50kpa. IF
you're still at 80 after IAC reset etc. you will need to look at intake sealing etc. for your vac leak. With the car running take a propane (UNLIT !!) and point it around the intake sealing areas (runners, base, plenum, etc.), when you hear the idle raise that is your leak. You can also try a differnet map sensor....