Having engine problems with 1994 LT1
Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
Having engine problems with 1994 LT1
Info about my C4:
1994 LT1
6 speed manual
118,000 miles
Previous owner did not know any information on previous service as he had the car passed down to him after his father passed away.
Owned the car since 115,000 miles
CEL Codes: H16, H32, H43, and H48
When I start the car up the engine RPMs drop to around 500 as if it is about to stall, but quickly picks back up to normal idle. Half the time I begin driving it after starting and waiting 15 or so seconds it will act like it is about to stall, so I depress the clutch. When the engine is no longer under load from the transmission it then runs absolutely fine. Engaging first gear again will cause the LT1 to act sputtery and hesitant, and does so until I have driven for a minute or two. After the minute or two it drives fine, although I get some occasional lack of power. The other half of the time the car will drive off fine with no issues at all. Most of the time I can drive the car hard and it will respond fine, but sometimes the heavy acceleration instead will lead to bogging and more stuttering. If I get bogging and stuttering I stop immediately and drive casually.
I have no idea what is wrong and would really appreciate it if someone had some ideas. I don’t have enough money to replace a bunch of things to see what works. I am definitely willing to try a few replacements that could be the issue, just don’t run me in circles.
Thanks!
1994 LT1
6 speed manual
118,000 miles
Previous owner did not know any information on previous service as he had the car passed down to him after his father passed away.
Owned the car since 115,000 miles
CEL Codes: H16, H32, H43, and H48
When I start the car up the engine RPMs drop to around 500 as if it is about to stall, but quickly picks back up to normal idle. Half the time I begin driving it after starting and waiting 15 or so seconds it will act like it is about to stall, so I depress the clutch. When the engine is no longer under load from the transmission it then runs absolutely fine. Engaging first gear again will cause the LT1 to act sputtery and hesitant, and does so until I have driven for a minute or two. After the minute or two it drives fine, although I get some occasional lack of power. The other half of the time the car will drive off fine with no issues at all. Most of the time I can drive the car hard and it will respond fine, but sometimes the heavy acceleration instead will lead to bogging and more stuttering. If I get bogging and stuttering I stop immediately and drive casually.
I have no idea what is wrong and would really appreciate it if someone had some ideas. I don’t have enough money to replace a bunch of things to see what works. I am definitely willing to try a few replacements that could be the issue, just don’t run me in circles.
Thanks!
Last edited by Snake2543; Jun 18, 2018 at 04:20 AM.
Racer
Joined: Dec 2017
Posts: 316
Likes: 63
From: Peoria IL
Snake, sorry for your trouble. I don't have enough experience to say whether it is the Opti or not. Sounds like it could be, but I'm not sure I'd just run with it as the diagnosis either. fake, what is it that convinces you to say with 100% certainty it is the Opti? Drop some wisdom on me (I admit my ignorance on the topic).
Snake, did you see this thread - similar? https://www.corvetteforum.com/forums...-no-start.html
Anyway if you decide the Opti is the problem, do a lot of research on replacements. I'm sure there are reliable replacements to be had. There's a ton of info on here about Optis, so take your time and do the diligence. FWIW, my brother in law has a 96 CE coupe. he just replace the Opti with one from O'Reilly's or Autozone, and it's working fine. So far. Personally, I'd soak up everything I could off this forum before buying a replacement Opti.
Snake, did you see this thread - similar? https://www.corvetteforum.com/forums...-no-start.html
Anyway if you decide the Opti is the problem, do a lot of research on replacements. I'm sure there are reliable replacements to be had. There's a ton of info on here about Optis, so take your time and do the diligence. FWIW, my brother in law has a 96 CE coupe. he just replace the Opti with one from O'Reilly's or Autozone, and it's working fine. So far. Personally, I'd soak up everything I could off this forum before buying a replacement Opti.
Last edited by turtle96; Jun 18, 2018 at 10:28 AM.
Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
Snake, sorry for your trouble. I don't have enough experience to say whether it is the Opti or not. Sounds like it could be, but I'm not sure I'd just run with it as the diagnosis either. fake, what is it that convinces you to say with 100% certainty it is the Opti? Drop some wisdom on me (I admit my ignorance on the topic).
Snake, did you see this thread - similar? https://www.corvetteforum.com/forums...-no-start.html
Anyway if you decide the Opti is the problem, do a lot of research on replacements. I'm sure there are reliable replacements to be had. There's a ton of info on here about Optis, so take your time and do the diligence. FWIW, my brother in law has a 96 CE coupe. he just replace the Opti with one from O'Reilly's or Autozone, and it's working fine. So far. Personally, I'd soak up everything I could off this forum before buying a replacement Opti.
Snake, did you see this thread - similar? https://www.corvetteforum.com/forums...-no-start.html
Anyway if you decide the Opti is the problem, do a lot of research on replacements. I'm sure there are reliable replacements to be had. There's a ton of info on here about Optis, so take your time and do the diligence. FWIW, my brother in law has a 96 CE coupe. he just replace the Opti with one from O'Reilly's or Autozone, and it's working fine. So far. Personally, I'd soak up everything I could off this forum before buying a replacement Opti.
I’ll check out that thread, thanks!
Last edited by Snake2543; Jun 18, 2018 at 07:33 PM.
Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
Well, here’s an update.
Drove the car around a bit today, and looked at cars at a dealership to pass time. When I went to start the car it started but very roughly. It ran for a couple seconds then died, and it would not start up after that. Had to have it towed to an auto repair shop.
I seriously suspect that the optispark is my issue now. The engine would crank and attempt to spark, but acted like it wasn’t getting fuel. Throws my concerns for the possibility being a really shitty MAF out the window. Suppose it could be the fuel pump or somewhere else along the fuel path, but only time will tell. We’ll see what the shop says. Bad day!
Drove the car around a bit today, and looked at cars at a dealership to pass time. When I went to start the car it started but very roughly. It ran for a couple seconds then died, and it would not start up after that. Had to have it towed to an auto repair shop.
I seriously suspect that the optispark is my issue now. The engine would crank and attempt to spark, but acted like it wasn’t getting fuel. Throws my concerns for the possibility being a really shitty MAF out the window. Suppose it could be the fuel pump or somewhere else along the fuel path, but only time will tell. We’ll see what the shop says. Bad day!
Racer
Joined: Dec 2017
Posts: 316
Likes: 63
From: Peoria IL
Sucks having to get towed. Who has the car? Do you have a good Vette shop you trust? I haven't had my car long and always want to have a go to for repairs I may not be able to do myself. Anyway, hope to hear back when you know more about what's going on with your car.
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Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
I can’t vouch too much for how good they are. My dad brought his V10 Excursion to them years ago after an accident causing engine damage. They completely fixed the thing and it ran for years after. This makes me confident they can replace simple Opti (which I am nearly 100% positive is the issue now). I would replace it myself but I refuse to potentially replace the wrong part, I don’t have the money to throw parts at it, so I’m biting the bullet and spending a little extra to make sure it’s the correct part.
I’ll keep you updated
Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
Opti was not the issue. Injectors, thermostat, and PCM connectors were. All replaced with 3 hours of labor for $410
Now I just need to find out what the idle issue is.
New codes are: H71, H27, H32 (existing code), and H72. All are relating to PCM other than one, which relates to the EGR. I believe PCM may just be temporary and those codes will clear with time, my issue now may be the EGR. (Could be entirely wrong).
Shrocks did great work fixing the issues that caused me to end up roadside. Can’t blame them to much for looking over the idle issue, although it idles better now than before. I will definitely be going back to them to have this “new” issue sorted out.
They also pointed out that my rear suspension should be replaced soon. It is squishy from age, which I realized already, but they say it is actually really bad for a C4. I will be replacing that soon, may even upgrade to a coilover setup and lower my car a little. (Not sure how much, less than an inch though because Illinois roads...)
(May have missed something, I wrote this once already and accidentally clicked an ad before I clicked finish lol)
Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
Seems I spoke too soon. Car killed over again, but it was acting different beforehand. I’m gonna bring it back over to Shrocks again and see what they can do. More updates eventually.
Race Director
Joined: Sep 2001
Posts: 14,676
Likes: 751
From: NEwhere Ohio
Optispark.
Be aure to install a custom vent harness or convert over to gen2 optispark while at it (you will need to replace cam and timing cover to do that).
whatever optispark you use must use an oem quality mitaubishi optical sensor.
Someone was saying there is a guy on ebay from ohio that will install a mitaubishi optical sensor into an msd replacement optispark. People here have reported good luck with it. Though i cant remember if he does gen 1 92-94 or gen 2 95-96 or both...
good luck
Be aure to install a custom vent harness or convert over to gen2 optispark while at it (you will need to replace cam and timing cover to do that).
whatever optispark you use must use an oem quality mitaubishi optical sensor.
Someone was saying there is a guy on ebay from ohio that will install a mitaubishi optical sensor into an msd replacement optispark. People here have reported good luck with it. Though i cant remember if he does gen 1 92-94 or gen 2 95-96 or both...
good luck
Thread Starter
Heel & Toe
Joined: Feb 2018
Posts: 19
Likes: 0
From: Mackinaw Illinois
Optispark.
Be aure to install a custom vent harness or convert over to gen2 optispark while at it (you will need to replace cam and timing cover to do that).
whatever optispark you use must use an oem quality mitaubishi optical sensor.
Someone was saying there is a guy on ebay from ohio that will install a mitaubishi optical sensor into an msd replacement optispark. People here have reported good luck with it. Though i cant remember if he does gen 1 92-94 or gen 2 95-96 or both...
good luck
Be aure to install a custom vent harness or convert over to gen2 optispark while at it (you will need to replace cam and timing cover to do that).
whatever optispark you use must use an oem quality mitaubishi optical sensor.
Someone was saying there is a guy on ebay from ohio that will install a mitaubishi optical sensor into an msd replacement optispark. People here have reported good luck with it. Though i cant remember if he does gen 1 92-94 or gen 2 95-96 or both...
good luck
Safety Car
Joined: Jan 2004
Posts: 4,549
Likes: 343
From: Glastonbury CT
Bring it to a Corvette shop or you will be throwing parts at it!. These cars OB1 show codes that mean nothing. A good shop will have i believe Tech 1 Diagostic tool. for your car. As far as optis there are many on the market vented or non vented. I have MSD and a rebuilt AC on the car now. I would recomend Petris in Alabama as a unit. He has been a C4 guru since the opti was born .That new Opti as far as new means nothing unless you have a warranty on it. The best opti is an original if you can find one. Good Luck
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