Help, ruff idle
Thread Starter
Pro
Joined: Oct 2010
Posts: 520
Likes: 30
From: Mooresville NC
Help, ruff idle
HELP! 2002 Corvette 48,000 miles ruff idle climbs to about 1100 rpms then goes down to almost stall, back up, back down. And not just when it's cold, when its warm too.
No codes no check engine.
What do you think?
Thanks in advance. Frank
No codes no check engine.
What do you think?
Thanks in advance. Frank
Drifting
Joined: Jul 2013
Posts: 1,603
Likes: 798
From: Windsor CA
2024 C7 of the Year Finalist - Unmodified
I know a long shot but is the MAP sensor clean?
Drifting
Joined: Jul 2013
Posts: 1,603
Likes: 798
From: Windsor CA
2024 C7 of the Year Finalist - Unmodified
It is just behind the air cleaner assembly, about 2" piece of aluminum. If you clean it make sure and use a can of mass air flow sensor cleaner and not brake cleaner. should only take about 10 minutes, made my ruff idle at times go away.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Its called a MAF Sensor... Mass Air Flow Sensor. You have to remove the air filter assembly and SPRAY it clean. YES, also clean the throttle body/throttle blade.
Also look at the PCV rubber fittings and see is there are any that are rotted.
LS1
LS6/2004
The rubber boot around the PCV where it connects to the manifold can and will rot and leak.
Also look at the PCV rubber fittings and see is there are any that are rotted.
LS1
LS6/2004
The rubber boot around the PCV where it connects to the manifold can and will rot and leak.
Thread Starter
Pro
Joined: Oct 2010
Posts: 520
Likes: 30
From: Mooresville NC
Yeah, MAF that's what I thought he meant. I did check the PCV hoses and they are fine I even changed the PCV just to rule that out.
Will Pull the MAF sensor this week and clean that as suggested.
What are the chances that the MAF is just bad and why am I not getting any codes?
Also could it be a bad fuel pump?
Will Pull the MAF sensor this week and clean that as suggested.
What are the chances that the MAF is just bad and why am I not getting any codes?
Also could it be a bad fuel pump?
Last edited by goodguys282; Sep 30, 2013 at 02:58 PM.
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
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The MAF can be bad and still have an output. When it doesnt have an output or its so far off that its out of range (according to the PCM) you will get a DTC.
Are you reading the DTCs with in the ignition ON cycle when the problem occurs. In other words, with the engine RUNNING.
Bill
Are you reading the DTCs with in the ignition ON cycle when the problem occurs. In other words, with the engine RUNNING.
Bill
Thread Starter
Pro
Joined: Oct 2010
Posts: 520
Likes: 30
From: Mooresville NC
UPDATE, I took the throttle body off completely and cleaned it with throttle body cleaner and a tooth brush (not mine
) and also the MAF with MAF cleaner. NO CHANGE.
Stopped to see Kelly at PCM Performance here in Mooresville, they specialize in GM Tuning. She suggested that the TPS may be bad. Not sure how to test it but isn't that part of the throttle body? I dont think I can buy that separately.
) and also the MAF with MAF cleaner. NO CHANGE. Stopped to see Kelly at PCM Performance here in Mooresville, they specialize in GM Tuning. She suggested that the TPS may be bad. Not sure how to test it but isn't that part of the throttle body? I dont think I can buy that separately.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The TPS is a multi sensor variable resistor. It has two phases and the output from each phase is equal but oposite in voltage. I PHASE A is .5 VDC, PHASE B willl be 4.50 VDC.
Normally when the TPS is bad, it throwa a code and can and will go into reduced engine power.
I guess its possible that it could be bad but, I would make sure that I not getting unmetered air from the ducting between the TB abd MAF.
Normally when the TPS is bad, it throwa a code and can and will go into reduced engine power.
I guess its possible that it could be bad but, I would make sure that I not getting unmetered air from the ducting between the TB abd MAF.
Melting Slicks
Joined: Nov 2009
Posts: 2,922
Likes: 219
From: West Branch, MI
I had this problem when I did engine mods. Turned out it was a vacuum leak. I had two new injectors that didn't seal properly. The extra air entering the intake would be read by the engine and it would add fuel to compensate, then it would almost die, then back up, and so on. Look for a vacuum leak around the intake and see if that doesn't resolve your issue.
Drifting
Joined: Feb 2008
Posts: 1,596
Likes: 67
From: Bahama North Carolina
The TPS is a multi sensor variable resistor. It has two phases and the output from each phase is equal but oposite in voltage. I PHASE A is .5 VDC, PHASE B willl be 4.50 VDC.
Normally when the TPS is bad, it throwa a code and can and will go into reduced engine power.
I guess its possible that it could be bad but, I would make sure that I not getting unmetered air from the ducting between the TB abd MAF.
Normally when the TPS is bad, it throwa a code and can and will go into reduced engine power.
I guess its possible that it could be bad but, I would make sure that I not getting unmetered air from the ducting between the TB abd MAF.
Last edited by BigGun; Oct 2, 2013 at 06:37 PM. Reason: tying to be nice
Thread Starter
Pro
Joined: Oct 2010
Posts: 520
Likes: 30
From: Mooresville NC
The TPS is a multi sensor variable resistor. It has two phases and the output from each phase is equal but oposite in voltage. I PHASE A is .5 VDC, PHASE B willl be 4.50 VDC.
Normally when the TPS is bad, it throwa a code and can and will go into reduced engine power.
I guess its possible that it could be bad but, I would make sure that I not getting unmetered air from the ducting between the TB abd MAF.
Normally when the TPS is bad, it throwa a code and can and will go into reduced engine power.
I guess its possible that it could be bad but, I would make sure that I not getting unmetered air from the ducting between the TB abd MAF.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The ducting between the TB and the MAF, all the vacuum lines and fittings , injector seals, TB seal, manifold tightness, all need to be correct to keep out any air. All the air INTO the engine needs to go through the MAF so that it is properly accounted for and the proper fuel is added to maintain the proper AFR.
If you have a vacuum leak,, it will cause idle issues and effect your efficiency.
A simple way of determining if there is a leak at a joint and or sealing surface is to spray brake parts cleaner on the area. If the idle changes when the joint is sprayed, the combustible fluid is getting past the seal.
You can also use the gas from an UN-LIT Propane torch.
BC
If you have a vacuum leak,, it will cause idle issues and effect your efficiency.
A simple way of determining if there is a leak at a joint and or sealing surface is to spray brake parts cleaner on the area. If the idle changes when the joint is sprayed, the combustible fluid is getting past the seal.
You can also use the gas from an UN-LIT Propane torch.
BC
Thread Starter
Pro
Joined: Oct 2010
Posts: 520
Likes: 30
From: Mooresville NC
Well the car finally spit out some codes today.
Along with a reduced power on the DIC
P1120
P1220
P1516
C1278
I ordered a TP Sensor tonight should have it in a couple of days.
Thanks for all the helpful tips guys
Along with a reduced power on the DIC
P1120
P1220
P1516
C1278
I ordered a TP Sensor tonight should have it in a couple of days.
Thanks for all the helpful tips guys