"surging" when the rpm drops.
Thread Starter
Team Owner
Joined: Feb 2000
Posts: 51,504
Likes: 6
From: Sacramento CA
"surging" when the rpm drops.
If I rev it up in neutral, as it goes down it sounds like this:
2.5k Vrrrrr...
2k Vrrrr..
1.75k BRURRR
1.7k Rrr..Vrrr..
1.5k vrrrrr
1.25k vrrrr
1k BRURURUR
740 Rrrvrrr
600 vrrrrrrrrrrrrrrrrrrrrrrrrr....
It stopped after i put new plugs in, but started again the same day. Performance seems alright, and gas mileage seems to be on target.
Any ideas? Dirty injector?
2.5k Vrrrrr...
2k Vrrrr..
1.75k BRURRR
1.7k Rrr..Vrrr..
1.5k vrrrrr
1.25k vrrrr
1k BRURURUR
740 Rrrvrrr
600 vrrrrrrrrrrrrrrrrrrrrrrrrr....
It stopped after i put new plugs in, but started again the same day. Performance seems alright, and gas mileage seems to be on target.
Any ideas? Dirty injector?
Safety Car
Joined: Feb 2000
Posts: 4,564
Likes: 110
From: Austin Texas
Re: "surging" when the rpm drops. (Smash)
Most likely it is the IAC (Idle Air Control) servo that is either dirty or about ready to go out.
This is fairly common on the L98's. The IAC is the solenoid on the throttle body front, bottom right (from seat) and either the spring is going out, the motor is going out, or the seat that the plunger seals against has a carbon build-up on it.
This is fairly common on the L98's. The IAC is the solenoid on the throttle body front, bottom right (from seat) and either the spring is going out, the motor is going out, or the seat that the plunger seals against has a carbon build-up on it.
Team Owner
Joined: Apr 2000
Posts: 27,818
Likes: 8
From: CT
Re: "surging" when the rpm drops. (Joe90)
Smash.....
My car would start/stall start/stall. Then, it'd learn the procedure back and run fine. two days later, start/stall start/stall. replaced the IAC... ZERO troubles.
My car would start/stall start/stall. Then, it'd learn the procedure back and run fine. two days later, start/stall start/stall. replaced the IAC... ZERO troubles.
Thread Starter
Team Owner
Joined: Feb 2000
Posts: 51,504
Likes: 6
From: Sacramento CA
Re: "surging" when the rpm drops. (JD 90 383)
Hmn.. you know, twice its started, and stalled if i let off the gas. in other words, i had to keep the idle up.. HMN.. The part cant be too expensive, or hard to replace. Right?
Are there any adjustments, or is it just in and out?
Are there any adjustments, or is it just in and out?
Safety Car
Joined: Feb 2000
Posts: 4,564
Likes: 110
From: Austin Texas
Re: "surging" when the rpm drops. (Smash)
Just replace it. The IAC cycles on start-up from open to closed and back open again. This tells the computer where it is. No adjustments necessary.
While you have the throttle body off, it's a good time to clean out the plenum, install the coolant bypass and I'd even replace the TPS (Throttle Position Sensor) while I was in there. Check your shaft bushings to see if they are worn out. If it wiggles a little, replace the throttle body. Air leaking past the shaft can wreak havok with the computer trying to optimize the idle circuit.
All together, figure an afternoon (2-3 hours tops) to finish it.
While you have the throttle body off, it's a good time to clean out the plenum, install the coolant bypass and I'd even replace the TPS (Throttle Position Sensor) while I was in there. Check your shaft bushings to see if they are worn out. If it wiggles a little, replace the throttle body. Air leaking past the shaft can wreak havok with the computer trying to optimize the idle circuit.
All together, figure an afternoon (2-3 hours tops) to finish it.
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
