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Surging in '94

9

'94Tripleblack

Guest
Anyone have the problem of high idleing/surging? It idles up over 1000RPMS while stopped. Optispark? it's been to 4 places and not one scope can detect a spike.
 

Rob

Site Administrator
Staff member
Administrator
Joined
Sep 16, 2000
Messages
13,589
Location
New Hampshire
Corvette
1990 Corvette ZR-1
Michelle,

I would have them check out the IAC valve (Idle Air Control Valve). Carbon deposits can build up on the inside of the valve and effect normal operation. Sometimes the valve can just be cleaned, and other times, it may need to be totally replaced. A service mechanic should be able to determine if the valve is functioning properly and move from there. This is just one suggestion, but lets see what others suggest.
 

JT ZR-Won

Well-known member
Joined
Dec 6, 2000
Messages
1,273
Location
Bradenton, FL
Corvette
'90 ZR-1 #365 (SOLD...but Dad's got it now)
I agree with Rob. If the IAC sensor is not functioning properly, the car will still run great under throttle, but it just won't idle properly. If you do need a new Idle Air Control sensor, they're pretty inexpensive. Good Luck.....

Jay
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
HI there,
YOur theory on the Optispark may be correct.
Find a shop, with either a Tech 2 scan tool, or a digital storage oscilloscope.
Have them monitor the low resolution signal.
If this signal drops out, it defaults, thereby increasing the idle.
IAC can also be controlled, and monitored, however, you may find that the IAC is being commanded higher by the PCM, as a result of the missing signal.
Bestoyou, c4c5
 
9

'94Tripleblack

Guest
It WAS the Opti!!!! $1,000 later.
 

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