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help misfire after header install

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Old Jul 25, 2011 | 04:42 PM
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Default help misfire after header install

hey guys trying to work out the kinks so when i start the car when she is cold it runs rough and throws the p3000 right away when it warms up it runs good but when i WOT it and after 4000rpm it missfires like crazy and backfires and throws the code again. so i need the experts opinon here what did i screw up lol. are the plugs cracked? wires bad? o2's bad? the rear o2's are hooked up corectly i have the plugs reversed so left plug hooked to right side and vise versa and all wiring and plugs have been checked
these are stainless works headers with cats 1 7/8 and 3" pipes
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Old Jul 25, 2011 | 04:50 PM
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From: Tomball Texas
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Originally Posted by livinloud
hey guys trying to work out the kinks so when i start the car when she is cold it runs rough and throws the p3000 right away when it warms up it runs good but when i WOT it and after 4000rpm it missfires like crazy and backfires and throws the code again. so i need the experts opinon here what did i screw up lol. are the plugs cracked? wires bad? o2's bad? the rear o2's are hooked up corectly i have the plugs reversed so left plug hooked to right side and vise versa and all wiring and plugs have been checked
these are stainless works headers with cats 1 7/8 and 3" pipes
Sounds like you cracked more than one plug. Anyway, replace all the plugs and check for any wires you may have seperated. Good place to start.
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Old Jul 25, 2011 | 05:05 PM
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From: Tomball Texas
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I managed to crack two plugs during my header install. Never threw a missfire code, however under heavy load I could feel the surge.

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Old Jul 25, 2011 | 06:27 PM
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ok i pulled the plugs and the two middle ones on the drivers side are cracked will change plugs tomorrow and share results
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Old Jul 25, 2011 | 07:04 PM
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Originally Posted by livinloud
ok i pulled the plugs and the two middle ones on the drivers side are cracked will change plugs tomorrow and share results
Should be all set with new plugs!
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Old Jul 25, 2011 | 08:58 PM
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Also check ground on driver side block
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Old Jul 26, 2011 | 01:47 AM
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I was going to say wires or cracked plugs but since you found two cracked plugs you're on the right track. The wires though almost always get destroyed if they've been on there awhile.
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Old Jul 26, 2011 | 06:01 AM
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Not sure how the plugs get cracked when installing headers.
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Old Jul 26, 2011 | 06:55 AM
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From: mississauga ontario
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I was super careful when taking off the wires I would trun and pull so they all came Off in one piece. The ground on the back of the block is on. I think the Plugs must get damaged when your trying to muscle in the headers and they have to be super brittle from all the heat cycles
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Old Jul 26, 2011 | 07:51 AM
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Originally Posted by vettenuts
Not sure how the plugs get cracked when installing headers.
Because a few don't take the TIME/EFFORT to pull the plugs before
doing their install.

Pretty hard not to mess up a plugs porcelain when manuvering long tubes in these tight engine bays of the Corvette.
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Old Jul 26, 2011 | 09:24 AM
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From: Tomball Texas
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[QUOTE=bumble-z;1578234871]Because a few don't take the TIME/EFFORT to pull the plugs before
doing their install.

For me its not an issue of effort. I think we can all agree that pulling the plugs once the manifolds are off is cake. I would rather replace them once the headers are on to make sure nothing enters a cylinder while wrestling the headers in place. If I had someone helping on the install I might change the procedure up.
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Old Jul 26, 2011 | 09:44 AM
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[QUOTE=SLVRCPE;1578235455]
Originally Posted by bumble-z
Because a few don't take the TIME/EFFORT to pull the plugs before
doing their install.

For me its not an issue of effort. I think we can all agree that pulling the plugs once the manifolds are off is cake. I would rather replace them once the headers are on to make sure nothing enters a cylinder while wrestling the headers in place. If I had someone helping on the install I might change the procedure up.
What's wrong with removing them BEFORE removing the stock manifolds?? If not time & effort?

Push paper towel into each plug cyl after removing ea plug. can't get any more straight forward than that.


By the way, I installed my long tubes by myself, on jack stands with out the aid of another set of hands.
Main thing is do the research & have a plan to do the job properly. Less hassle that way.

Last edited by bumble-z; Jul 26, 2011 at 11:11 AM.
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Old Jul 26, 2011 | 11:01 AM
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From: Tomball Texas
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[QUOTE=bumble-z;1578235601]
Originally Posted by SLVRCPE

What's wrong with removing them BEFORE removing the stock manifolds?? If not time & effort?

Push paper towel into each plug cyl after removing ea plug. can't get any more straight forward than that.

By the way, I installed my long tubes by myself, on jack stands with out the aid of another set of hands.
Main thing is do the research & have a plan to do the job properly. Less hassle that way.
I must admit you have the very best method of installing headers, congrats!

OP - let us know how that beast runs with the new headers!

Last edited by SLVRCPE; Jul 26, 2011 at 11:19 AM.
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