HELP - Stumble and bad idle
Thread Starter
Drifting
Joined: Dec 2002
Posts: 1,474
Likes: 4
From: Tracy CA
HELP - Stumble and bad idle
I could use some help. I'm mechanically capable (replaced engines, torn apart gear sets, etc. ) this one has me stumped.
The 1992 Corvette LT1 w/M6 has an idle/off idle stumble or misfire. Replaced the plugs with NGK TR55 platinums, the wires have 10000 miles on them, replaced the O2 sensors, checked the EGR solenoid...
The opti was replaced 10,000 miles ago with the dynaspark unit.
The misfire occurs primarily when the engine is completely warmed up and between idle and right off idle.
I'm going to replace the pcv valve just because it's so cheap - but I have no expectations of that helping.
Where should I start to look? Injectors? Ignition? computer?
The 1992 Corvette LT1 w/M6 has an idle/off idle stumble or misfire. Replaced the plugs with NGK TR55 platinums, the wires have 10000 miles on them, replaced the O2 sensors, checked the EGR solenoid...
The opti was replaced 10,000 miles ago with the dynaspark unit.
The misfire occurs primarily when the engine is completely warmed up and between idle and right off idle.
I'm going to replace the pcv valve just because it's so cheap - but I have no expectations of that helping.
Where should I start to look? Injectors? Ignition? computer?
Melting Slicks
Joined: Sep 2003
Posts: 2,270
Likes: 118
From: N. Babylon NY
Hi,
My 1992 M6 is also missing. I pulled all the plugs and noticed that many were gas fouled. The car sat for about 6 months so I thought it might be bad gas (I did add fuel stablizer at that time). I drained as much as I could get out and added fresh fuel and cleaneed all the plugs. When I started it up it ran better but still missed. I also noticed that 1 cat was glowing red hot.
In my case I do not think that it is ign related. I have purchsed new fuel injectors (from forum vendor FIC) but have not installed yet. I will start a new thread when I figure this out.
I would start with pulling your plugs and see how they look. Keep us updated!
Steve
My 1992 M6 is also missing. I pulled all the plugs and noticed that many were gas fouled. The car sat for about 6 months so I thought it might be bad gas (I did add fuel stablizer at that time). I drained as much as I could get out and added fresh fuel and cleaneed all the plugs. When I started it up it ran better but still missed. I also noticed that 1 cat was glowing red hot.
In my case I do not think that it is ign related. I have purchsed new fuel injectors (from forum vendor FIC) but have not installed yet. I will start a new thread when I figure this out.
I would start with pulling your plugs and see how they look. Keep us updated!
Steve
Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
I would start with ohm checking the fuel injectors.
Check the sticky at the top of this forum from Fuel Injector Connection! Jon shows you how to check the injectors in a video. Way cool.
Jon is the BEST vendor I have had the pleasure of doing business with.
Search for FIC on this forum and see all the recommendations for his company and product.
The early Multec fuel injectors are very suspect. Low miles or many miles cause them to fail. So, we are all stuck between a rock and a very hard place!
SAVE the WAVE!
Check the sticky at the top of this forum from Fuel Injector Connection! Jon shows you how to check the injectors in a video. Way cool.
Jon is the BEST vendor I have had the pleasure of doing business with.
Search for FIC on this forum and see all the recommendations for his company and product.
The early Multec fuel injectors are very suspect. Low miles or many miles cause them to fail. So, we are all stuck between a rock and a very hard place!
SAVE the WAVE!
Team Owner
Joined: Oct 2000
Posts: 96,443
Likes: 9
From: Fort Knox, KY
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Inspect the wires in the dark or a darkened area of your garage. Open the hood, pull the hood light fuse, then start the engine. Look for telltale arcing along the ignition and coil wire.
Your plug wires may not have that many miles no them, but that doesn't mean one or more hasn't failed prematurely.
It happens, especially with AC/Delco's waning quality of foreign made parts.
You can also mist the wires with a spray bottle to "exorcise" plug wire gremlins.
Your plug wires may not have that many miles no them, but that doesn't mean one or more hasn't failed prematurely.
It happens, especially with AC/Delco's waning quality of foreign made parts.
You can also mist the wires with a spray bottle to "exorcise" plug wire gremlins.
Last edited by onedef92; Aug 4, 2009 at 01:42 PM.
Thread Starter
Drifting
Joined: Dec 2002
Posts: 1,474
Likes: 4
From: Tracy CA
I would start with ohm checking the fuel injectors.
Check the sticky at the top of this forum from Fuel Injector Connection! Jon shows you how to check the injectors in a video. Way cool.
Jon is the BEST vendor I have had the pleasure of doing business with.
Search for FIC on this forum and see all the recommendations for his company and product.
The early Multec fuel injectors are very suspect. Low miles or many miles cause them to fail. So, we are all stuck between a rock and a very hard place!
SAVE the WAVE!
Check the sticky at the top of this forum from Fuel Injector Connection! Jon shows you how to check the injectors in a video. Way cool.
Jon is the BEST vendor I have had the pleasure of doing business with.
Search for FIC on this forum and see all the recommendations for his company and product.
The early Multec fuel injectors are very suspect. Low miles or many miles cause them to fail. So, we are all stuck between a rock and a very hard place!
SAVE the WAVE!
I replaced the PCV valve.
No change.
Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
Well, we know the electrical windings in your injectors are good. What we do not know is if the mechanical parts of your injectors are working.
I would give Jon at Fuel Injector Connection a call. He will speak with you personally about what can fail inside of the Multec fuel injector.
Whether you go with his remanufactured Bosch Design III or his new Bosch Design III, you will end up with a superior product with superior engineering compared to your OEM Multecs.
I have a feeling that your Multecs are starting to fail. Call Jon and see what he has to say.
Also, check out this thread which chronicles my experiences:
http://forums.corvetteforum.com/c4-t...long-read.html
SAVE the WAVE!
I would give Jon at Fuel Injector Connection a call. He will speak with you personally about what can fail inside of the Multec fuel injector.
Whether you go with his remanufactured Bosch Design III or his new Bosch Design III, you will end up with a superior product with superior engineering compared to your OEM Multecs.
I have a feeling that your Multecs are starting to fail. Call Jon and see what he has to say.
Also, check out this thread which chronicles my experiences:
http://forums.corvetteforum.com/c4-t...long-read.html
SAVE the WAVE!
Thread Starter
Drifting
Joined: Dec 2002
Posts: 1,474
Likes: 4
From: Tracy CA
Update - did the paper clip trick to get codes. Just a historic 72 and 74.
TorchRedlt4Man: Thanks for the inputs on the injectors. I'm not quite buying into it just yet because the thing works better cold than hot.
Next step: wire replacement.
It'll be a week or so till I get back to this.
TorchRedlt4Man: Thanks for the inputs on the injectors. I'm not quite buying into it just yet because the thing works better cold than hot.
Next step: wire replacement.
It'll be a week or so till I get back to this.
Thread Starter
Drifting
Joined: Dec 2002
Posts: 1,474
Likes: 4
From: Tracy CA
Hi,
My 1992 M6 is also missing. I pulled all the plugs and noticed that many were gas fouled. The car sat for about 6 months so I thought it might be bad gas (I did add fuel stablizer at that time). I drained as much as I could get out and added fresh fuel and cleaneed all the plugs. When I started it up it ran better but still missed. I also noticed that 1 cat was glowing red hot.
In my case I do not think that it is ign related. I have purchsed new fuel injectors (from forum vendor FIC) but have not installed yet. I will start a new thread when I figure this out.
I would start with pulling your plugs and see how they look. Keep us updated!
Steve
My 1992 M6 is also missing. I pulled all the plugs and noticed that many were gas fouled. The car sat for about 6 months so I thought it might be bad gas (I did add fuel stablizer at that time). I drained as much as I could get out and added fresh fuel and cleaneed all the plugs. When I started it up it ran better but still missed. I also noticed that 1 cat was glowing red hot.
In my case I do not think that it is ign related. I have purchsed new fuel injectors (from forum vendor FIC) but have not installed yet. I will start a new thread when I figure this out.
I would start with pulling your plugs and see how they look. Keep us updated!
Steve
I don't have these handy clues.
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Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
I am sure the replacement of your ignition wires will do nothing to repair your problem. Well, at least 90% sure! Let us know how it goes!
SAVE the WAVE!
Melting Slicks
Joined: Sep 2003
Posts: 2,270
Likes: 118
From: N. Babylon NY
I will post my results!
Steve
Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
SAVE the WAVE!
Team Owner
Joined: Oct 2000
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From: Fort Knox, KY
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These HEI ignitions are very sensitive to proper coil wire insulation.
Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
That's not always true. My wires were bad, but performed fine when the engine was cold. Once things got hot under there, it began missing and sputtering like mad. New coil and plug wires cured my problem.
These HEI ignitions are very sensitive to proper coil wire insulation.
These HEI ignitions are very sensitive to proper coil wire insulation.
As a normal rule of thumb: Electrical issues are more dependent on high temperatures.
I did say: (for the most part!) In my mind, this would equate to: That's not always true.
Glad to see your fix was a relatively easy one. A lot of people end up chasing a solution to a cold/hot running problem for a long time.
SAVE the WAVE!
Last edited by TorchRedlt4man; Aug 5, 2009 at 10:55 AM.
Team Owner
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From: Fort Knox, KY
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What's the verdict on the injectors?
Thread Starter
Drifting
Joined: Dec 2002
Posts: 1,474
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From: Tracy CA
The new ICM is installed. Still have the problem. I suppose a scan check is in order. To date, I've installed:
NGK TR55P spark plugs
Taylor Wires (2 years old)
Bosch O2 sensors
PCV Valve
A new Coil
A new ICM
I suppose the only things left are to replace the wires (oldest thing on there) fuel injectors and opti (which is a Dynaspark - they'll check it out, rebuild it for like $60).
NGK TR55P spark plugs
Taylor Wires (2 years old)
Bosch O2 sensors
PCV Valve
A new Coil
A new ICM
I suppose the only things left are to replace the wires (oldest thing on there) fuel injectors and opti (which is a Dynaspark - they'll check it out, rebuild it for like $60).