Sudden High Surging Idle ?
 

Hello,
I was out for a ride recently and all of a sudden my idle went from steady 900-1000 to varying 1000 to 1500-1800. I checked for vacuum leaks, checked the base timing and made sure the tps was at .98. I am running a 75 mm/ma and a 70 mm/tb, gt40 heads 24 lb inj. a ford "F" cam and a Diablo chip.
Any idea's ??

Re: Sudden High Surging Idle ?
 

Suggest to check the system for codes, running a KOEO/KOER self-test. Also check the TPS @op temp, for flat spots/spikes on the output voltage, Ign On, while slowly moving the accelerator blade from closed throttle to WOT, back and forth, this condition could also cause erratic high/low idle problems. The other possibility could be a sticking IAC valve. My 2¢.

Re: Sudden High Surging Idle ?
 

Thank You for the reply, I will try your suggestions.

Re: Sudden High Surging Idle ?
 

Pull codes first to make sure it isn't EGR related. If the TPS isn't new I'd change that first. Then clean the IAC, and check all vacuum lines. If you hear no squeels from losing vacuum then you may need a brand new IAC. Good Luck!