plugs, wires, hot exhaust=headache

[purple c4]

HELP! started my 95 LT1 and it seemed to only run on about 7 cylinders, lost about 300 rpm and 5 miles a gallon of fuel. Still ran smooth just down a little on power and fuel mileage, changed plugs drove it about 1,000 miles still the same, changed wires, when I did the 4 wires in the right side I started the car after and it was the same, when I did the left side I started the car and it ran worse, will backfire at idle sometimes, does not run as smooth as before I changed the wires, exhaust on that side will get orange hot at pipe just before cat converter, any ideas? Plug wires are not crossed, I think my initial problem may have been a wire on that side, could I have blocked the cat converter because I drove it not running correctly? Exhaust got glowing hot after about 15 minutes of idleing on the left side only, thank you so much in advance, I'm lost.

 

[tmkassin]

If you have a cloged cat you will have low vacuum. Put a gage on it and see how it reads. You may also have cracked a plug during installation. If one cylinder is not firing you are pouring raw gas into the exhaust. This will cause your computer to lean out that bank of injectors and this will cause backfiring.

 

[Hib Halverson]

First, stop running the car until the exhaust glows. All that will do (if it hasn't already) is damage your cat converter. Once you learn how much they cost, you'll regret getting the exhaust that hot.

Second, is the check engine light on and if so, what code is set?

With the symptoms listed above, at this point, my guesses are that either the converter on that side is plugged, that side of the engine is way rich or that side of the engine has a misfire. Further diagnosis will be required to determine which it is.

One question I have....first you said the engine seems to be running on seven cylinders but then you say it runs smooth. If it's running on 7, it won't be running smooth. Can you be a little more specific about whether it's missing or smooth?

Good luck.

 

[LLC5]

HELP! started my 95 LT1 and it seemed to only run on about 7 cylinders, lost about 300 rpm and 5 miles a gallon of fuel. Still ran smooth just down a little on power and fuel mileage, changed plugs drove it about 1,000 miles still the same, changed wires, when I did the 4 wires in the right side I started the car after and it was the same, when I did the left side I started the car and it ran worse, will backfire at idle sometimes, does not run as smooth as before I changed the wires, exhaust on that side will get orange hot at pipe just before cat converter, any ideas? Plug wires are not crossed, I think my initial problem may have been a wire on that side, could I have blocked the cat converter because I drove it not running correctly? Exhaust got glowing hot after about 15 minutes of idleing on the left side only, thank you so much in advance, I'm lost.

It sounds like you have a cylinder misfire and the exhaust glowing hot is most likely because of the incomplete combustion and excessive oxygen in the exhaust caused by the misfire. Try removing one spark plug wire at a time and then run the engine to see if the engine runs the same or worse, if it runs the same you have found the bad cylinder, if it runs worse then you know that cylinder is hitting.

 

[purple c4]

First, stop running the car until the exhaust glows. All that will do (if it hasn't already) is damage your cat converter. Once you learn how much they cost, you'll regret getting the exhaust that hot.

Second, is the check engine light on and if so, what code is set?

With the symptoms listed above, at this point, my guesses are that either the converter on that side is plugged, that side of the engine is way rich or that side of the engine has a misfire. Further diagnosis will be required to determine which it is.

One question I have....first you said the engine seems to be running on seven cylinders but then you say it runs smooth. If it's running on 7, it won't be running smooth. Can you be a little more specific about whether it's missing or smooth?

Good luck.

Thanks for your help, did not know the exhaust was that hot until I looked under car, when the problem first occured the engine lost rpm and power but after I raised the rpm it ran smooth, just still down on power and gas mileage, changed plugs, no better, kept driveing car, changed wires about at least 1,000 miles later that's when it started to misfire and run rough, before I put the new wires on the exhaust was normal, car was down on power a little and I lost about 5 miles a gallon on fuel, I think I found #5 plug wire bad when I changed them, wires are on correct, no plugs are cracked, I felt the exhaust at the end of each pipe and one does not seem to be stronger than the other as far I can tell. Figured that would be an indication of a plugged cat, but don't really know, thank you again for your help, you guys are greatly appreciated! The check engine light is not on, and there are no codes. All plugs are fireing.The air pump is on at idle when I start car goes off at about 1200 or so rpm.

 

[purple c4]

It sounds like you have a cylinder misfire and the exhaust glowing hot is most likely because of the incomplete combustion and excessive oxygen in the exhaust caused by the misfire. Try removing one spark plug wire at a time and then run the engine to see if the engine runs the same or worse, if it runs the same you have found the bad cylinder, if it runs worse then you know that cylinder is hitting.

All cylinders are hitting, put a plug test light on which showed each one fireing, also removed wires one at a time and car ran worse each wire removed, thank you for the reply, I appreciate your time, please let me know if you can think of anything else, thanks, Jim

 

[purple c4]

If you have a cloged cat you will have low vacuum. Put a gage on it and see how it reads. You may also have cracked a plug during installation. If one cylinder is not firing you are pouring raw gas into the exhaust. This will cause your computer to lean out that bank of injectors and this will cause backfiring.

Thank you for your time and advice, don't have a vacuum guage but will get one this week, do you know where the proper place to draw vacuum is? Long hours at work limits the amount of time I have to work on car but I will take your advice and check that, thank you again for your time and help, Jim.

 

[Hib Halverson]

Thanks for your help,(snip)

You're welcome.
We owners of Dark Purple Metallic cars gotta stick together!

It sounds like your engine is no longer misfiring that and my assumption that the check engine light is not on have me thinking you ought to be looking at a faulty cat converter.

If your check engine light has been on, what codes are set?

 

[purple c4]

You're welcome.
We owners of Dark Purple Metallic cars gotta stick together!

It sounds like your engine is no longer misfiring that and my assumption that the check engine light is not on have me thinking you ought to be looking at a faulty cat converter.

If your check engine light has been on, what codes are set?

Thank you again for your continued help, the problem has been solved, it seems the clown who put the wires on and was sure they were on correct crossed cylinders 3 and 5, because the distributor is so hard to see it took me about 8 hours to find my mistake, taught me a lesson, no matter how many times you have done a particular job it is never routine, not in my world. Corvette runs just great now, waiting for the rain to stop so I can go for a ride, thanks again for your help and time! Jim Bannon

 

[boomdriver]

WOW !
i wonder just how far out those cylinders were? The spark had to be wayyy off at best, with the ECM trying to retard against knock...Electronic confusion in the control system.
Glad you got it figured out before it damaged itself.