Sparkplug gap and boosting 9psi.

G

Gabi

Member
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2003.5 Mica Yellow MSP
So I went and bought copper spark plugs in the stock heat range and gapped them at .29 now every time I go over 5psi (I'm running 9 psi) the car will start misfiring like a mofo. Is it because I should get a step colder plugs or is the gap wrong?
Thanks for the help.
 
gap is fine as long as it's between .028-.032. However, you could try gapping a little closer. are you sure it's misfiring? Is it throwing a code or blinking CEL?
 
An exhaust leak at the manifold is possible, before the primary 02. Sounds like the plugs have too wide of a gap still if the spark is blowing out under boost.
 
hornsfan10609 said:
An exhaust leak at the manifold is possible, before the primary 02. Sounds like the plugs have too wide of a gap still if the spark is blowing out under boost.
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The stock Mani was replaced with a steedspeed Mani maybe 7 months ago. What would you suggest I gap them to?
 
Supposed to be .028-.030", my car has always ran really well with this gap. Are you using a good gauge? It may be the coils or wires but it sounds exactly like what happens when you throw in plugs with too wide of a gap. You can try to reset the computer and remove and reinstall the coils/wires to re-seat them.
 
hornsfan10609 said:
Supposed to be .028-.030", my car has always ran really well with this gap. Are you using a good gauge? It may be the coils or wires but it sounds exactly like what happens when you throw in plugs with too wide of a gap. You can try to reset the computer and remove and reinstall the coils/wires to re-seat them.
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I'll go ahead and replace the wires but for now I'll reset the ecu. I have a prosport boost gauge but Im replacing that with an AEM unit.
Thanks for the help!
 
when i had that problem it was my coil packs failing, but not completely failed.
 
If the only thing you did was change plugs why not start there first?....do you still have the old ones, if your do slap them back on....start wih the obvious before chasing ghosts. If your car ran before changing wires why would you change them? Unless when you took em out you seriously mishandled them
 
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It's possible for the wires to be damaged upon removal, if the plugs and coils are new the wires should be replaced as well.
 
TURBOJ1 said:
Isn't it MUCH easier to just put the old plugs back in? Try that first! He said all he did was change plugs
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I changed the plugs because I thought foul plugs were causing the misfire. When I checked them they were still good but gapped incorrectly at .35. I even thought initially the colder weather was causing it. I'm getting both the coils and wires tomorrow, I'll keep you guys posted.
Thanks for the help everyone.
 
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So status report. I replaced both coil packs..... Turns out I was already running a duralast coil and 1 stock coil.... Both were replaced with new coil packs. I wasn't able to change out the wires because no one has the NGK on stock so I have to wait for those to come in. The car is still misfiring. I'm debating just getting some duralast cables just to rule that out. Suggestions anyone. By the way the a/f ratio goes pig rich right before it starts to misfire.
 
Be sure you try closing the gap more before you throw more money at it. Pig rich is the norm for these cars until you get into tuning
 
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