That's where I would start.
EM headers, Corsa, now it back fires?
Thread Starter
Melting Slicks
Joined: Mar 2005
Posts: 2,351
Likes: 228
From: Northeast FL
EM headers, Corsa, now it back fires?
Quick question. Car is a 94 with stock internals. Minor external mods such as SLP intake, Spiro pro wires, camber brace, etc.
Just put on Exotic Muscle long tube headers, Random Tech cats, and the Corsa cat-back. Now it has a very noticeable miss at idle (like it has a really big cam) and when you give it a little gas (in neutral) when you let off the gas it back fires. Loud, not just a little cough. It idled very smoothly before the exhaust was put on. We did have to remove the plugs and wires but have checked those twice to make sure they are secure.
Could it be that the ECM has to learn the new airflow so it needs to adjust the air fuel mixture? If so, how long does it take for the new settings to take affect? The battery was disconnected for two days while we did the install so it should have reset I would have thought.
Just put on Exotic Muscle long tube headers, Random Tech cats, and the Corsa cat-back. Now it has a very noticeable miss at idle (like it has a really big cam) and when you give it a little gas (in neutral) when you let off the gas it back fires. Loud, not just a little cough. It idled very smoothly before the exhaust was put on. We did have to remove the plugs and wires but have checked those twice to make sure they are secure.
Could it be that the ECM has to learn the new airflow so it needs to adjust the air fuel mixture? If so, how long does it take for the new settings to take affect? The battery was disconnected for two days while we did the install so it should have reset I would have thought.
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
THe 94 ECM doesn't realy learn so I doubt that has any thing to do with it. It could be the car has leaned out because of the exhaust and may need a tweek to the tune, ask Alvin about this one. What it sounds like to me is what happened to me a week ago and it was a burnt plug wire. I had almost the exact same indications the car seemed to have a slight miss, go figure, and it would back fire under light throttle. It only takes a second to check the wires so I would start with the simple things.
Team Owner
Joined: Sep 2001
Posts: 62,146
Likes: 1,730
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Check for spark to each cylinder, check fuel system out. I'm assuming there are no codes and the opti never got wet. It could be the O2s giving you trouble.
You would need a scanner to do that properly.
You would need a scanner to do that properly.
Thread Starter
Melting Slicks
Joined: Mar 2005
Posts: 2,351
Likes: 228
From: Northeast FL
Thanks guys.
Merle at EM said it might just be a loose wire too. Wires are new, about 100 miles, and with the headers on it only ran for about three minutes. The miss wasn't there before the headers and it was there immediately when we fired it up so I don't think it's a burnt wire. It may be a broken insulator on a plug too.
Nothing goes easy does it?
Merle at EM said it might just be a loose wire too. Wires are new, about 100 miles, and with the headers on it only ran for about three minutes. The miss wasn't there before the headers and it was there immediately when we fired it up so I don't think it's a burnt wire. It may be a broken insulator on a plug too.
Nothing goes easy does it?
Safety Car
Joined: Feb 2004
Posts: 3,786
Likes: 0
From: Minneapolis MN
Originally Posted by jwt1603
Thanks guys.
Merle at EM said it might just be a loose wire too. Wires are new, about 100 miles, and with the headers on it only ran for about three minutes. The miss wasn't there before the headers and it was there immediately when we fired it up so I don't think it's a burnt wire. It may be a broken insulator on a plug too.
Nothing goes easy does it?
Merle at EM said it might just be a loose wire too. Wires are new, about 100 miles, and with the headers on it only ran for about three minutes. The miss wasn't there before the headers and it was there immediately when we fired it up so I don't think it's a burnt wire. It may be a broken insulator on a plug too.
Nothing goes easy does it?
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
Likes: 71
From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by redvette6spd
I was going to ask if you removed or your plugs for the install a friend just did headers on his new c6 and cracked one it caused him a bunch of BS
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Thread Starter
Melting Slicks
Joined: Mar 2005
Posts: 2,351
Likes: 228
From: Northeast FL
Originally Posted by Corvette Kid NC
This is what I'm thinking too. I don't think you can put headers in place on a C4 w/ the plugs in, I never could. It's either a damaged plug or a connection/wire problem, I'd bet on it. What kind of wires did you install? Routed properly, I don't think the wires should otherwise be a problem (in the boot area) with the EMs.
Going to try again tonight and see what happens.
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
Likes: 71
From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by jwt1603
We removed the plugs before we started. It was fairly obvious that it wasn't going to happen with them in. The wires are new Spiro Pros from Taylor.
Going to try again tonight and see what happens.
Going to try again tonight and see what happens.
Thread Starter
Melting Slicks
Joined: Mar 2005
Posts: 2,351
Likes: 228
From: Northeast FL
Pulled the plug wires and plugs tonight. Found one that was dirty and wet. Wire must not have been seated all the way. Cleaned it up and put it back in. Idle is back to nice and smooth. It coughed once when the throttle was blipped but then seemed fine.
Can't really take it out and try it, raining so hard you can't see across the street. No, it's not a garage queen, but no sense driving it in bad weather when I really don't have to.
Thanks to all.
By the way the EM LT headers seem to be well made and Merle is great to deal with. The Corsa sounds good too. With the Random Tech cats everything fit very nicely and bolted right up.
Can't wait for the auto cross this weekend.
Can't really take it out and try it, raining so hard you can't see across the street. No, it's not a garage queen, but no sense driving it in bad weather when I really don't have to.
Thanks to all.
By the way the EM LT headers seem to be well made and Merle is great to deal with. The Corsa sounds good too. With the Random Tech cats everything fit very nicely and bolted right up.
Can't wait for the auto cross this weekend.
Le Mans Master
Joined: Oct 2002
Posts: 7,178
Likes: 1
From: Bahston Mass.
Originally Posted by jwt1603
Pulled the plug wires and plugs tonight. Found one that was dirty and wet. Wire must not have been seated all the way. Cleaned it up and put it back in. Idle is back to nice and smooth. It coughed once when the throttle was blipped but then seemed fine.
Can't really take it out and try it, raining so hard you can't see across the street. No, it's not a garage queen, but no sense driving it in bad weather when I really don't have to.
Thanks to all.
By the way the EM LT headers seem to be well made and Merle is great to deal with. The Corsa sounds good too. With the Random Tech cats everything fit very nicely and bolted right up.
Can't wait for the auto cross this weekend.
Can't really take it out and try it, raining so hard you can't see across the street. No, it's not a garage queen, but no sense driving it in bad weather when I really don't have to.
Thanks to all.
By the way the EM LT headers seem to be well made and Merle is great to deal with. The Corsa sounds good too. With the Random Tech cats everything fit very nicely and bolted right up.
Can't wait for the auto cross this weekend.
Glad your case worked out so easily - Enjoy
Instructor
Joined: Jun 2005
Posts: 161
Likes: 0
From: Toronto Ontario
I had similiar problems after my EM headers, RT cats, Corsa install. I relplaced my O2 sensors with HEATED O2 sensors and the problems went away. They are a little tricky becuase you have to wire the sensors to a power source but they work great.
I am not sure if your 94 has heated O2 sensors or not (I know the 92's do not).
I am not sure if your 94 has heated O2 sensors or not (I know the 92's do not).
