Issue after installing new plugs
Thread Starter
Burning Brakes
Joined: Aug 2007
Posts: 917
Likes: 2
From: Charlotte NC
Issue after installing new plugs
I installed new spark plugs today on my 94 and now it misses bad during acceleration only. Idle is nice and smooth, and even normal driving and high rpm's it's is nice and smooth.
It only misses at 50% or more throttle. as long as I stay below 50% throttle it drives just as it should.
The plugs I installed are Bosch +2 plugs that did not need gaped. Is it possible that the plugs where gaped wrong from the factory?
Since It only misses under heavy acceleration, It don't feel like I damaged a plug wire. To me it feels more like a fuel issue. However, the only thing I messed with was the plugs and it was running fine before I changed the plugs. Oh and I stayed far away from the opti.
What do you guys think is my issue? Bad/miss gap plugs? Broken plug wire? Other??
thanks.
It only misses at 50% or more throttle. as long as I stay below 50% throttle it drives just as it should.
The plugs I installed are Bosch +2 plugs that did not need gaped. Is it possible that the plugs where gaped wrong from the factory?
Since It only misses under heavy acceleration, It don't feel like I damaged a plug wire. To me it feels more like a fuel issue. However, the only thing I messed with was the plugs and it was running fine before I changed the plugs. Oh and I stayed far away from the opti.
What do you guys think is my issue? Bad/miss gap plugs? Broken plug wire? Other??
thanks.
Team Owner
Joined: Feb 2003
Posts: 54,124
Likes: 9,438
From: Sitting in his Nowhere land Hanover Pa
2024 C2 of the Year Finalist - Unmodified
2015 C2 of Year Finalist
Team Owner
Joined: Aug 2005
Posts: 34,988
Likes: 515
From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
Had that issue with NGK, the second I took them off and installed AC Rapid Fire the BS went away.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 413
From: WV
The only 2 things it could be is a plug or a wire, shouldn't be to hard to figure out..Don't rule out a bad plug just because there new, I have had quite a few bad plugs that were new....WW
Last edited by WW7; May 1, 2011 at 09:37 PM.
Burning Brakes
Joined: Aug 2010
Posts: 924
Likes: 10
From: Manteca Calif
Push on the wire until you hear a snap.....agree on the AC Rapid Fire 
http://parts-catalog.acdelco.com/cat...log_search.php look here for your correct part
http://parts-catalog.acdelco.com/cat...log_search.php look here for your correct part
Last edited by overdrawn; May 1, 2011 at 09:50 PM.
Thread Starter
Burning Brakes
Joined: Aug 2007
Posts: 917
Likes: 2
From: Charlotte NC
All the wires are on tight, I always double check my wires. A crossed wire is a slight possibility since I had to remove two of them at once on the driver side. ( Although I thought I had them marked correctly.) and a damaged wire is always possible when changing only the plugs.
My fear is it is the gap of the plugs. I purchased the plugs on line a long time ago and I'm concerned that they may have been damaged during shipping.
I looked at each one before I installed them and I did not notice any damage. But, how far off would the gap need to be to make an engine run bad?
My fear is it is the gap of the plugs. I purchased the plugs on line a long time ago and I'm concerned that they may have been damaged during shipping.
I looked at each one before I installed them and I did not notice any damage. But, how far off would the gap need to be to make an engine run bad?
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
Drifting
Joined: May 2007
Posts: 1,426
Likes: 165
From: Motor City
What was the gap? did you check before installing?
Most likely a crossed wire. Pull injector harnesses one at a time and see which two do not affect the idle when unplugged. Swap those two wires, should be pretty easy to find.
If that's not the case and the gaps are correct, I would consider throwing those Bosch plugs in the trash.
Most likely a crossed wire. Pull injector harnesses one at a time and see which two do not affect the idle when unplugged. Swap those two wires, should be pretty easy to find.
If that's not the case and the gaps are correct, I would consider throwing those Bosch plugs in the trash.
Instructor
Joined: Jan 2011
Posts: 165
Likes: 0
From: Eureka Ca
I never install new plugs without checking the gap. I agree that the C4 does not like Bosch, but that is what I run in the BMW, it must be a German thing I guess. I have AC in the Vette and it runs great.
dws
dws
Heel & Toe
Joined: Jan 2010
Posts: 15
Likes: 1
From: Charlotte
Diffently double and triple check wiring. I did mine, but found problem was on the opti. Having someone uptop pulling the wires one at a time was what I needed to double check everything and found the problem. Good Luck!