Performance Issue
Thread Starter
5th Gear
Joined: Jun 2018
Posts: 5
Likes: 0
From: Gilbert Arizona
Performance Issue
Hello everyone. My name is Peter Nicola. I have a 1994 with performance issues. The car is fine at idle, when taking off, it bogs down. If i hit the petal hard, it will eventually get up and go.
Within the last month, I have had the mass air flow replaced, egr sensor, fuel filter, and injectors replaced. This issue seems to be intermittent. Some times it runs fine, then starts driving like crap again. I have had it looked at by 2 reputable shops. Nobody seems to be able to figure this out. The computer I'm told, does not throw any codes.
Has anyone ever heard of something like this? Any input would be greatly appreciated.
In the last couple years I have done the cats, mufflers, plugs, wires, optispark, water pump, and probably also more I'm not thinking of. Ready to call it quits with the C4.
Within the last month, I have had the mass air flow replaced, egr sensor, fuel filter, and injectors replaced. This issue seems to be intermittent. Some times it runs fine, then starts driving like crap again. I have had it looked at by 2 reputable shops. Nobody seems to be able to figure this out. The computer I'm told, does not throw any codes.
Has anyone ever heard of something like this? Any input would be greatly appreciated.
In the last couple years I have done the cats, mufflers, plugs, wires, optispark, water pump, and probably also more I'm not thinking of. Ready to call it quits with the C4.
Drifting
Joined: Aug 2009
Posts: 1,964
Likes: 242
Check the below linked thread out which has a YouTube link on how to check for codes. This way you can confirm for yourself that there are none rather than rely on someone else telling you there aren’t any.
https://www.corvetteforum.com/forums...ble-codes.html
They're old cars and can be frustrating when not running right, but really rewarding when sorted out. Don’t throw the towel in just yet. Start with checking for codes yourself and let us know if you find any or none.
https://www.corvetteforum.com/forums...ble-codes.html
They're old cars and can be frustrating when not running right, but really rewarding when sorted out. Don’t throw the towel in just yet. Start with checking for codes yourself and let us know if you find any or none.
Racer
Joined: Jul 2017
Posts: 422
Likes: 53
From: PA
Hello everyone. My name is Peter Nicola. I have a 1994 with performance issues. The car is fine at idle, when taking off, it bogs down. If i hit the petal hard, it will eventually get up and go.
Within the last month, I have had the mass air flow replaced, egr sensor, fuel filter, and injectors replaced. This issue seems to be intermittent. Some times it runs fine, then starts driving like crap again. I have had it looked at by 2 reputable shops. Nobody seems to be able to figure this out. The computer I'm told, does not throw any codes.
Has anyone ever heard of something like this? Any input would be greatly appreciated.
In the last couple years I have done the cats, mufflers, plugs, wires, optispark, water pump, and probably also more I'm not thinking of. Ready to call it quits with the C4.
Within the last month, I have had the mass air flow replaced, egr sensor, fuel filter, and injectors replaced. This issue seems to be intermittent. Some times it runs fine, then starts driving like crap again. I have had it looked at by 2 reputable shops. Nobody seems to be able to figure this out. The computer I'm told, does not throw any codes.
Has anyone ever heard of something like this? Any input would be greatly appreciated.
In the last couple years I have done the cats, mufflers, plugs, wires, optispark, water pump, and probably also more I'm not thinking of. Ready to call it quits with the C4.
Don't see fuel pump in the parts replaced list. Did you check fuel pressure? Not just at idle, screw the gauge hose on to the test port, tape the gauge to the windshield, watch the gauge when it bogs. If all that checks out, most likely ignition.
Racer
Joined: Apr 2018
Posts: 349
Likes: 55
If that checks out, I would also recommend checking each injector with a probe light just to make sure they are firing.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,214
From: Park City Utah
Check fuel pressure while the symptom is occurring.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
Hello Peter !!...With the parts that you did replace were the electrical inputs checked ??...MAF, fuel injectors, EGR ??....as they say..."garbage in, garbage out"...let's assume power and grounds checked out... yes, I'd check for fuel pressure and I'd add the TPS Sensor in there...it might be going a little wonky on you !!...P.S. Cleaning the TB wouldn't hurt either !!
Last edited by C5 Diag; Jun 29, 2018 at 04:55 PM.
Racer
Joined: Mar 2014
Posts: 267
Likes: 24
From: Montevideo, Uruguay
My 93 had exactly the same symptoms as yours, I tried, checked and changed everything that can be imagined without positive results.
Finally one day, it occurred to me to disconnect the knock sensors and at that moment it started to run perfect.
Obviously it threw a check engine light and turned on the fans, but despite that, the car was running like a champ.
I ordered a chip from PCM of NC and reconnect the sensors.
This was 5 years ago and to this day I am still amazed at how well it still runs.
I do not know if a 94 has a chip, if it has one it is an easy fix and not very expensive and if it does not have one, I suppoe something can be done with the computer.
I understand your situation and I just want to provide an idea.
good luck!!
Finally one day, it occurred to me to disconnect the knock sensors and at that moment it started to run perfect.
Obviously it threw a check engine light and turned on the fans, but despite that, the car was running like a champ.
I ordered a chip from PCM of NC and reconnect the sensors.
This was 5 years ago and to this day I am still amazed at how well it still runs.
I do not know if a 94 has a chip, if it has one it is an easy fix and not very expensive and if it does not have one, I suppoe something can be done with the computer.
I understand your situation and I just want to provide an idea.
good luck!!
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Thread Starter
5th Gear
Joined: Jun 2018
Posts: 5
Likes: 0
From: Gilbert Arizona
I did replace the fuel pump last year.
Thread Starter
5th Gear
Joined: Jun 2018
Posts: 5
Likes: 0
From: Gilbert Arizona
Follow up to my issue. It ended up being the optispark. I took it apart and one of the screws inside had come loose or broken off. Makes sense why at higher speeds I didn't have an issue as it was rotating faster. Luckily it was lifetime warranty, just got me for labor.