engine problems, help please
Thread Starter
Team Owner
Joined: Aug 2012
Posts: 31,626
Likes: 12
From: Sacramento California
engine problems, help please
Hey,
so my car has had some knocking issues in the past, 93 LT1 engine
and now all the sudden when i get to about 55 mph it starts to really knock and like cut out. i talked to another c4 guy in the area and he thinks its not getting enough fuel and a fuel line or pump problem.
basically it runs fine and accelerates fine up until about 55mph and then when i accelerate, and the harder i try, the worse it gets to the point of the pedal kicking back at me (not caused by asr, turned asr off)
and i am really worried about the engine.
any thoughts? i just had the dealer service the rear differential and power steering and they didnt notice anything in there inspection.
anyone know a good place to go, or just go to the dealer in town? (santa rosa)
it there anyway to diagnose this problem??
help please!!!!
thank you!!!
just to add, it starts by knocking a bit, then more, then it feels like the engine is cutting out and i slow down and that is when the pedal comes back at me. the more i pushed it the worse it got so now i dont push it past 2k rpm
so my car has had some knocking issues in the past, 93 LT1 engine
and now all the sudden when i get to about 55 mph it starts to really knock and like cut out. i talked to another c4 guy in the area and he thinks its not getting enough fuel and a fuel line or pump problem.
basically it runs fine and accelerates fine up until about 55mph and then when i accelerate, and the harder i try, the worse it gets to the point of the pedal kicking back at me (not caused by asr, turned asr off)
and i am really worried about the engine.
any thoughts? i just had the dealer service the rear differential and power steering and they didnt notice anything in there inspection.
anyone know a good place to go, or just go to the dealer in town? (santa rosa)
it there anyway to diagnose this problem??
help please!!!!
thank you!!!
just to add, it starts by knocking a bit, then more, then it feels like the engine is cutting out and i slow down and that is when the pedal comes back at me. the more i pushed it the worse it got so now i dont push it past 2k rpm
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Okay well try getting the highest octane gas that you have available to you, and see if it still knocks, use up all the old gas first though. If it still knocks buy a bottle of octane booster and put it in the tank and drive it. If it goes away then you are dealing with a spark knock issue, which is more of a relief. If it still knocks then you are probably dealing with a mechanical engine knock.
Remember, if it is spark knock, this can be deadly. Spark knock is like taking a hammer and hitting your piston full force. It can destroy your engine in a matter of seconds, so not good to try to reproduce it while it is still a problem. If it is spark knock, then you would be looking at things that can control your A/F ratio. If all those check out, you want to check out timing and your timing control components. If you are not getting enough voltage to the spark plug, you may get some spark knock.
Spark knock happens when the engine runs too lean.
Edit: I just re-read your paragraph, and that sounds like it may be a mechanical knock. Sorry
Remember, if it is spark knock, this can be deadly. Spark knock is like taking a hammer and hitting your piston full force. It can destroy your engine in a matter of seconds, so not good to try to reproduce it while it is still a problem. If it is spark knock, then you would be looking at things that can control your A/F ratio. If all those check out, you want to check out timing and your timing control components. If you are not getting enough voltage to the spark plug, you may get some spark knock.
Spark knock happens when the engine runs too lean.
Edit: I just re-read your paragraph, and that sounds like it may be a mechanical knock. Sorry
Last edited by DanielRicany; Jan 11, 2014 at 03:05 AM.
Thread Starter
Team Owner
Joined: Aug 2012
Posts: 31,626
Likes: 12
From: Sacramento California
Okay well try getting the highest octane gas that you have available to you, and see if it still knocks, use up all the old gas first though. If it still knocks buy a bottle of octane booster and put it in the tank and drive it. If it goes away then you are dealing with a spark knock issue, which is more of a relief. If it still knocks then you are probably dealing with a mechanical engine knock.
Remember, if it is spark knock, this can be deadly. Spark knock is like taking a hammer and hitting your piston full force. It can destroy your engine in a matter of seconds, so not good to try to reproduce it while it is still a problem. If it is spark knock, then you would be looking at things that can control your A/F ratio. If all those check out, you want to check out timing and your timing control components. If you are not getting enough voltage to the spark plug, you may get some spark knock.
Spark knock happens when the engine runs too lean.
Edit: I just re-read your paragraph, and that sounds like it may be a mechanical knock. Sorry
Remember, if it is spark knock, this can be deadly. Spark knock is like taking a hammer and hitting your piston full force. It can destroy your engine in a matter of seconds, so not good to try to reproduce it while it is still a problem. If it is spark knock, then you would be looking at things that can control your A/F ratio. If all those check out, you want to check out timing and your timing control components. If you are not getting enough voltage to the spark plug, you may get some spark knock.
Spark knock happens when the engine runs too lean.
Edit: I just re-read your paragraph, and that sounds like it may be a mechanical knock. Sorry
what does mechanical knock mean? what is the problem or what can i do to fix that issue?
thank you!
also i have always put in the highest octane gas i can get, 91, never have used octane boost before.
also at 100k (its at 104k now) i had the spark plugs replaced, but not the wires, could the wiring be an issue. it definitely gets worse the harder i pushed it so it sounds like that tells you something. i am going to avoid repeating it by only doing city driving until i can get it to a mechanic ASAP
Last edited by Lord.Baal; Jan 11, 2014 at 04:11 AM.
Le Mans Master
Joined: Jul 2009
Posts: 6,381
Likes: 66
From: SF bay area C.A.
C4 of the Year Finalist
Sean, I know you had a pinging issue at the autox, is it a knock or ping? When you brought it over for your check engine light it ran real good.
Last edited by kimmer; Jan 11, 2014 at 09:11 AM.
Melting Slicks
Joined: Jan 2009
Posts: 3,181
Likes: 286
From: Puyallup Washington
I would suggest that you get on the proper regional forum and ask for assistance in diagnosing the problem. You will find people with lots of knowledge that are willing to come and listen to your car.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
thanks for the help,
what does mechanical knock mean? what is the problem or what can i do to fix that issue?
thank you!
also i have always put in the highest octane gas i can get, 91, never have used octane boost before.
also at 100k (its at 104k now) i had the spark plugs replaced, but not the wires, could the wiring be an issue. it definitely gets worse the harder i pushed it so it sounds like that tells you something. i am going to avoid repeating it by only doing city driving until i can get it to a mechanic ASAP
what does mechanical knock mean? what is the problem or what can i do to fix that issue?
thank you!
also i have always put in the highest octane gas i can get, 91, never have used octane boost before.
also at 100k (its at 104k now) i had the spark plugs replaced, but not the wires, could the wiring be an issue. it definitely gets worse the harder i pushed it so it sounds like that tells you something. i am going to avoid repeating it by only doing city driving until i can get it to a mechanic ASAP
Thread Starter
Team Owner
Joined: Aug 2012
Posts: 31,626
Likes: 12
From: Sacramento California
I am not sure if it is pinging or knocking, it sounded like pinging at first but now it feels a lot harder then that. like the engine is cutting out. it could be backfiring, i wouldnt be able to tell the difference between those 3 different problems, just that the engine is making a strange noise and is cutting out as it gets pushed harder.
i just called the dealer up here and am going to have the corvette mechanic take a look at it to try to diagnose the problem, i dont want to keep repeating it if it is damaging the engine.
thanks for the help!
i just called the dealer up here and am going to have the corvette mechanic take a look at it to try to diagnose the problem, i dont want to keep repeating it if it is damaging the engine.
thanks for the help!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
Thread Starter
Team Owner
Joined: Aug 2012
Posts: 31,626
Likes: 12
From: Sacramento California
i wish i could tell the different between knocking and pinging
Race Director
Joined: Feb 2002
Posts: 11,599
Likes: 1,053
From: Compound in the Grove, Ga.
2026 Corvette of the Year Finalist - Unmodified
2025 C4 of the Year Winner - Unmodified
2024 C4 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
2019 C4 of Year Finalist (performance mods)
2018 C4 of Year Finalist
2015 C4 of the Year Finalist
St. Jude Donor '16
Just a thought how's the exhaust flow? Think your cats could be stopped up?
Thread Starter
Team Owner
Joined: Aug 2012
Posts: 31,626
Likes: 12
From: Sacramento California
i hope its something like timing that can be fixed, not something i can do but hopefully the chevy mechanic can take care of it quickly.
and i would say no, it doesnt sound like chatter, more like pinging then just stopping
thanks for all the thoughts, i am not very mechanical but anything i might be able to test myself would be helpful, hoping the dealer will be able to give me a good answer when i take it in
Race Director
Joined: Feb 2002
Posts: 11,599
Likes: 1,053
From: Compound in the Grove, Ga.
2026 Corvette of the Year Finalist - Unmodified
2025 C4 of the Year Winner - Unmodified
2024 C4 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
2019 C4 of Year Finalist (performance mods)
2018 C4 of Year Finalist
2015 C4 of the Year Finalist
St. Jude Donor '16
I' not saying this is your issue just something to check, I had an 84 that stopped up the cats and it would not get past 3k rpms.
If your cats are stopped up the flow at the mufflers will be hot and slow, have someone step on the gas and it should increase. Your engine is like an air pump the more rpms the more air will pass through it, if the cats are stopped up it can't get the air out.
If your cats are stopped up the flow at the mufflers will be hot and slow, have someone step on the gas and it should increase. Your engine is like an air pump the more rpms the more air will pass through it, if the cats are stopped up it can't get the air out.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
I had a similar problem, but my 85 has very low compression I believe 9.0:1. It didn't knock, but you may have a problem with the computer controlling timing. Make sure your EST wire is plugged in, because when I left mine unplugged the car wouldn't go passed 4,000 RPMs.
Race Director
Joined: Feb 2002
Posts: 11,599
Likes: 1,053
From: Compound in the Grove, Ga.
2026 Corvette of the Year Finalist - Unmodified
2025 C4 of the Year Winner - Unmodified
2024 C4 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
2019 C4 of Year Finalist (performance mods)
2018 C4 of Year Finalist
2015 C4 of the Year Finalist
St. Jude Donor '16
I had a similar problem, but my 85 has very low compression I believe 9.0:1. It didn't knock, but you may have a problem with the computer controlling timing. Make sure your EST wire is plugged in, because when I left mine unplugged the car wouldn't go passed 4,000 RPMs.
Thread Starter
Team Owner
Joined: Aug 2012
Posts: 31,626
Likes: 12
From: Sacramento California
Kim, you totally called it. it was my EGR, it was totally shot, having it replaced tomorrow along with getting the injectors cleaned, had a lot of carbon buildup and was causing the pinging and loss of power.
really glad it was relatively cheap and nothing to serious, should have had that done as soon as you told me that was probably what was making it ping, you do know your 90's c4's!!!
really glad it was relatively cheap and nothing to serious, should have had that done as soon as you told me that was probably what was making it ping, you do know your 90's c4's!!!