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New build, backfiring at idle?

Discussion in 'New Edge Cobras' started by 01slobruh, Aug 26, 2019.

  1. 01slobruh

    01slobruh Member Established Member

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    Hi guys, I have a 01 procharged cobra, that I recently swapped a built 03 short block on with 04 heads that were just refreshed to stock specs. I reused my manifold.

    As soon as I start the car it'll start to backfire pretty constantly at idle. Im pretty sure there is no exhaust leaks, or vacuum leaks. I'm seeing 20lbs vacuum at idle. My fuel pressure does seem a little higher than I remember. I think it used to be 30 at idle but now it seems to be at 37 but it's been almost 5 months since I last had it running so my memory is foggy on that. Plugs are new tr6s gapped at .30.

    The car was tuned by lasota and it was pretty good before the swap. The only other difference other than the new block is the new longtubes. I'm getting a retune next week, but am just trying to see if you guys think this is a tuning or mechanical issue? Would longtubes be causing a backfire without a tune for them?

    Thanks for any input guys.
     
  2. 01slobruh

    01slobruh Member Established Member

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    Nvm figured it out, my car hates tr6s for some reason. Only likes Ngk br7ef's.
     
  3. slo984now

    slo984now AKA 01yellerCobra Established Member

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    That's weird. I've ran TR6's in multiple cars with no issues.

    I always say cars have personalities.
     
  4. 01slobruh

    01slobruh Member Established Member

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    On my original motor and after I I procharged it I swapped to tr6s gapped at .28 once. Flooded it right away.

    I thought for sure this time around on a built 03 block and with 04 heads, for sure she would like tr6s this time around. I was wrong. I played with the gap from .26 to .35 and same story. I dont get why.

    Screenshot_20190827-151156_Gallery.jpg
     
  5. slo984now

    slo984now AKA 01yellerCobra Established Member

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    I'm not doubting you at all. Do some searching in the Terminator section and the brand of plug varies. Some have no issues with the TR6. Others can only run iridiums. I'm glad I can run the TR6. Makes it cheap to swap them out.
     
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  6. 01slobruh

    01slobruh Member Established Member

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    Yea I was just under the assumption the tr6 was THE plug to run. Isn't the br7ef recommended for high boost? Which is what I dont get cause I only have a p1 with stock pulleys.

    I guess cars do have different personalities ‍
     
  7. Swannyvill

    Swannyvill BLOWN '01 Established Member

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