Sudden High Surging Idle ?

LXinProgress · 04-08-2006, 07:32 AM

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 ??

Joel5.0 · 04-08-2006, 09:38 PM

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¢.

LXinProgress · 04-08-2006, 10:12 PM

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

HoodStrype · 04-11-2006, 04:03 PM

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!

04-08-2006, 07:32 AM	#1
LXinProgress Registered Member Join Date: Jul 2005 Posts: 10	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 ??

04-08-2006, 09:38 PM	#2
Joel5.0 Registered Member Join Date: Oct 2005 Location: Sabana Grande, Puerto Rico Posts: 33	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¢. __________________ ACRONYMS: LUK=Let Us Know, GL=Good Luck, LMK=Let Me Know, JIC=Just In Case, BTSTDTRT=Been There Seen That Done That Repaired That and the classic... DILLIGAS=Do I Look Like I Give A S*** 1986 Mustang GT w/T-Tops NOW: 5.0L Stock SB, X303 Cam, 700 cfm DP Holley, 289 '66 Heads, 1.7 RR, Richmond Gear 4+1 Tranny, Centerforce DF, 2.73 Gears WIP: 3.90 Gears, LS Overhaul, Adj. LCA's & UCA's (Granatelli), T-Top weather striping and rear braces bodywork

04-08-2006, 10:12 PM	#3
LXinProgress Registered Member Join Date: Jul 2005 Posts: 10	Re: Sudden High Surging Idle ? Thank You for the reply, I will try your suggestions.

04-11-2006, 04:03 PM	#4
HoodStrype Rearview Mirror Haze Join Date: May 1999 Location: Huntsville, Alabama...a.k.a. "HuntsVegas" Posts: 387	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! __________________ 93 lx Notch 01 GT ...the epitome of Murphy's Law

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