Engine surges at idle
Pro
Joined: Oct 2002
Posts: 604
Likes: 0
From: CROSSING INTO CHARLOTTE NC FROM SC! SC
Re: Engine surges at idle (rebuild)
I have a '93 w/auto at idle theengine revs onits own. Anyone know what could cause this?
look into the distributor Opti Spark .
Seems like you are a bit new to the forum ... Whatever you do ...Do not hose your engine down!!
Good luck ...
Mark A.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Engine surges at idle (rebuild)
Are you getting any code(s);There are a number of things that could cause it. Here's a partial list:
Defective/malfunctioning
Sensor(s),
Injector(s),
Ignition timing
Fuel pressure/regulator
Vacuum leak,
Can you give any more details on what's happening?
Jake
Defective/malfunctioning
Sensor(s),
Injector(s),
Ignition timing
Fuel pressure/regulator
Vacuum leak,
Can you give any more details on what's happening?
Jake
Thread Starter
Advanced
Joined: Jan 2003
Posts: 82
Likes: 0
From: Yonkers NY
Re: Engine surges at idle (1990CORVETTE)
No codes while idling engine revs up maybe 300 rpms and drops back down, usually after its warm it probably does it cruising too but isn't as noticable. Sometimes if i gun it the car will hesitate a bit don't know if thats related.
Burning Brakes
Joined: Jul 2003
Posts: 933
Likes: 0
From: Rock Hill SC
Re: Engine surges at idle (rebuild)
I had the same symptoms and it ended up being my opti. Idle would surge while I was stopped and occasionaly stuuter as I took off. With mine it ran fine in the upper RPM's.
Racer
Joined: Jan 2002
Posts: 473
Likes: 8
From: Shreveport LA
Re: Engine surges at idle (rebuild)
Clean or replace the idle air control valve (IAC) on your throttle body. Also, with your engine turned off, make sure your throttle blades are completely closed when the throttle is not depressed. Otherwise your IAC will continue adjusting itself back & forth trying to solve the problem.
A bad IAC valve was causing my car to surge up & down about 500 rpm (more or less). Took me a while to figure out the problem.
A bad IAC valve was causing my car to surge up & down about 500 rpm (more or less). Took me a while to figure out the problem.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Re: Engine surges at idle (rebuild)
it's the opti. A sure sign that the cap/rotor assembly are badly carbon traced.
what happens is that at idle, a miss occurs. the engine computer manipulates timing, mixture and idle to make a fix, but then the engine runs ok, the computer resets to expected norms... and this game goes on.
annoying as hell....
it is not cost effective to replace just the cap and rotor. it requires the same amount of labour, so all you are saving is 200.00, and, costing, the need to do it again in a few short months.
replace the entire assembly.
also, there are options available now to replace the opti... or, at least get rid of the high voltage side - LTCC & Del-Teq have come up with coil systems that replace the high voltage. I have installed the LTCC and LOVE IT!
Dyna-Tech Engineering has redesigned the optispark unit.
take your pick.
keep us posted.
what happens is that at idle, a miss occurs. the engine computer manipulates timing, mixture and idle to make a fix, but then the engine runs ok, the computer resets to expected norms... and this game goes on.
annoying as hell....
it is not cost effective to replace just the cap and rotor. it requires the same amount of labour, so all you are saving is 200.00, and, costing, the need to do it again in a few short months.
replace the entire assembly.
also, there are options available now to replace the opti... or, at least get rid of the high voltage side - LTCC & Del-Teq have come up with coil systems that replace the high voltage. I have installed the LTCC and LOVE IT!
Dyna-Tech Engineering has redesigned the optispark unit.
take your pick.
keep us posted.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Pro
Joined: Oct 2002
Posts: 604
Likes: 0
From: CROSSING INTO CHARLOTTE NC FROM SC! SC
Re: Engine surges at idle (Dilligas)
I had the same symptoms and it ended up being my opti. Idle would surge while I was stopped and occasionaly stuuter as I took off. With mine it ran fine in the upper RPM's.
Is it me or do I see a trend of the Opti going out in all kinds of different fashion??
Everytime I talk to someone or hear about the opti I get a different symptom on how it went out... making it pretty frustrating to pinpoint.
Just an observation ....
PS Dilligas Love your Aqua Colored C4 ... I have an Aqua roadster and sometimes I wish it was either a coupe or it had a Hardtop!!
I'll leave my sig so ya can peep it!!
Mark A.
Burning Brakes
Joined: Jul 2003
Posts: 933
Likes: 0
From: Rock Hill SC
Re: Engine surges at idle (madquake)
PS Dilligas Love your Aqua Colored C4 ... I have an Aqua roadster and sometimes I wish it was either a coupe or it had a Hardtop!!
I'll leave my sig so ya can peep it!!
Mark A.
I'll leave my sig so ya can peep it!!
Mark A.
