i Have an s4 t2, emmisions and bac deleted. car runs perfectly, but the idle randomly changes. it'll idle nicely around 800, then during a short drive, go up to 1000, sometimes 1500. but it will go down and stay where its suppose to be if i slip the clutch a little bit, like say i roll forward a little. the idle screw is secure, tps is adjusted, no vacuum leaks. not sure what to check. my stock vert did the same once in a while as well.

 

I'd check the throttle plates,the linkage on the throttle body and also the cable.

 

Why do people delete the BAC and then complain about idle issues.

Sorry OP, not trying to harp on ya, but damn it's a thread a week.

 

To be fair, a missing BAC won't cause a high idle. It will just cause an unstable and unregulated idle.

As suggested, it sounds like something in the throttle body is sticking. Check cold start cam, check secondary throttle blades. Hose the whole throttle body down with brake cleaner and give it a good air blowing. Then spray penetrating oil, work all the shafts, then clean off all the oil.

 

And you may have a sticky clutch switch also. The Yellow/Blue wire at the switch and pin 1L at the ECU should read 12 volts w/the clutch depressed and less than 1.5 volts w/the clutch released.

 

didn't consider that, will check

Like i said, my stock vert randomly did it, so i know its not related to the bac. besides everything was removed years ago, problem just recently started.

going to clean it like you said, most likely needs a clean anyway.

I had voltage issues with the switch before, so i will look into that aswell