Thanks for the info.
96 LT4...stumble under load until 2k...no codes.
Thread Starter
Heel & Toe
Joined: Apr 2006
Posts: 21
Likes: 0
From: Texas
96 LT4...stumble under load until 2k...no codes.
I have a stumble under load (1/4 throttle or more) under 2000rpm. It cleans up, almost disappearing around 2k. For example, 3rd gear 1500 1/2 throttle it stumbles until 2000. 3rd gear 2200 1/2 - 3/4 throttle and no stumble. Of course it's more noticeable at lower rpm and lower gear. When it stumbles, it's like it's missing and knocks pretty bad until I back off the throttle. Here's the skinny:
No mods except cat back.
Opti is 3 yrs old but only about 1000 miles on it.
Plugs are 2 yrs old but only about 500 miles on them.
Wires are 1 yr old and only about 100 miles on them.
Checked for loose wires but all were tight. Changed out injectors with known good ones but no joy. Couldn't find any vacuum leaks. This rules out any major causes (fuel, spark). Could it be an O2 sensor? If so, 1st or 2nd? Possible cause is too much advance before the engine can use it, hence the knocking. But what would cause that? I don't get any codes. Bad O2? Does anything happen around 2k rpm like switching fuel maps/spark control? I don't want to spend too much more time/parts chasing it until I can narrow it down a little more. Would plugging a computer into it tell me something I can't see already? Does anyone know a good shop around here who does this?
Thanks for the help.
No mods except cat back.
Opti is 3 yrs old but only about 1000 miles on it.
Plugs are 2 yrs old but only about 500 miles on them.
Wires are 1 yr old and only about 100 miles on them.
Checked for loose wires but all were tight. Changed out injectors with known good ones but no joy. Couldn't find any vacuum leaks. This rules out any major causes (fuel, spark). Could it be an O2 sensor? If so, 1st or 2nd? Possible cause is too much advance before the engine can use it, hence the knocking. But what would cause that? I don't get any codes. Bad O2? Does anything happen around 2k rpm like switching fuel maps/spark control? I don't want to spend too much more time/parts chasing it until I can narrow it down a little more. Would plugging a computer into it tell me something I can't see already? Does anyone know a good shop around here who does this?
Thanks for the help.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
I have a stumble under load (1/4 throttle or more) under 2000rpm. It cleans up, almost disappearing around 2k. For example, 3rd gear 1500 1/2 throttle it stumbles until 2000. 3rd gear 2200 1/2 - 3/4 throttle and no stumble. Of course it's more noticeable at lower rpm and lower gear. When it stumbles, it's like it's missing and knocks pretty bad until I back off the throttle. Here's the skinny:
No mods except cat back.
Opti is 3 yrs old but only about 1000 miles on it.
Plugs are 2 yrs old but only about 500 miles on them.
Wires are 1 yr old and only about 100 miles on them.
Checked for loose wires but all were tight. Changed out injectors with known good ones but no joy. Couldn't find any vacuum leaks. This rules out any major causes (fuel, spark). Could it be an O2 sensor? If so, 1st or 2nd? Possible cause is too much advance before the engine can use it, hence the knocking. But what would cause that? I don't get any codes. Bad O2? Does anything happen around 2k rpm like switching fuel maps/spark control? I don't want to spend too much more time/parts chasing it until I can narrow it down a little more. Would plugging a computer into it tell me something I can't see already? Does anyone know a good shop around here who does this?
Thanks for the help.
No mods except cat back.
Opti is 3 yrs old but only about 1000 miles on it.
Plugs are 2 yrs old but only about 500 miles on them.
Wires are 1 yr old and only about 100 miles on them.
Checked for loose wires but all were tight. Changed out injectors with known good ones but no joy. Couldn't find any vacuum leaks. This rules out any major causes (fuel, spark). Could it be an O2 sensor? If so, 1st or 2nd? Possible cause is too much advance before the engine can use it, hence the knocking. But what would cause that? I don't get any codes. Bad O2? Does anything happen around 2k rpm like switching fuel maps/spark control? I don't want to spend too much more time/parts chasing it until I can narrow it down a little more. Would plugging a computer into it tell me something I can't see already? Does anyone know a good shop around here who does this?
Thanks for the help.
Contact forum vendor edcmat-l1
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
A bad TPS can also cause hiccups like you're experiencing. You can use a digital volt meter to see that the voltage increases smoothly - without sudden skips or jumps - as you open the butterflies.
Jake
My son, Ryan M. Cameron, graduated from West Point on 22 May 2010! He was commissioned as a 2nd Lieutenant and I pinned on his first pair of "Butter Bars" PROUDEST DAY OF MY LIFE!!
Jake
My son, Ryan M. Cameron, graduated from West Point on 22 May 2010! He was commissioned as a 2nd Lieutenant and I pinned on his first pair of "Butter Bars" PROUDEST DAY OF MY LIFE!!
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
