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Old 08-03-2010, 09:40 AM   #1
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Default Misfire under load.

Hello folks,


I have a problem with a misfire while at about 6psi of boost.....my car is a 1.8 mk1 1996 uk model.

I recently installed a MS1 V3 which I assembled myself, I have done the mods as per this site so I think the asemly is ok.

My problem is a misfire in boost, cruiseing and general driving about is fine, idle is good also. The misfire only happens when I put my foot to the floor and hold it ..afr,s are between 11.5 and 12.5 in boost so its not running lean.

Not sure if I have this right though, I have the one end of the shield on the ignition input wire connected to pin # 2 on the db37 and the other end of the shield connected to the chassis ground....is this right?


Not sure where to start with this so any advice would be great..


Cheers
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Old 08-03-2010, 09:46 AM   #2
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are you running highres?
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Old 08-03-2010, 09:48 AM   #3
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did you reduce your spark plug gap?
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Old 08-03-2010, 09:49 AM   #4
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Plug gaps?

What Plugs?
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Old 08-03-2010, 10:00 AM   #5
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Spark ******* plugs.
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Old 08-03-2010, 11:12 AM   #6
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Quote:
Originally Posted by Braineack View Post
Spark ******* plugs.
Our posts were just a few seconds apart.
We were essentially asking the same question, albeit with different wording, and neither of us had seen each other's posts when we hit the send button.

"What plugs" refers to the type of the plugs, rather than the nature of a "plug".

So there.
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Old 08-03-2010, 11:35 AM   #7
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gotcha !
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Old 08-03-2010, 11:42 AM   #8
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If you're already running stock plugz, my moneys are on plug wirez
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Old 08-03-2010, 03:04 PM   #9
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christ...don,t know what all this abuse is about. I only asked a simple question !!!!!!

My plugs are NGK BKR7E-11 haven,t changed the gap so they are what ever they are out of the pack .

Not using Highres.

Thanks for your help so far......
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Old 08-03-2010, 03:41 PM   #10
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they are 1.1mm (-11) out of the box, need to be closer to .030" (.76mm)
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Old 08-04-2010, 06:58 PM   #11
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Changed the plug gaps to .030" but still getting misfires....only seem to get them on hard acceleration.
Gentle acceeleration everything is fine even at 8psi ,hit the peddle hard and it misfires like mad,
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Old 08-04-2010, 07:44 PM   #12
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You might want to check the plug wires, especially the boots.
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Old 08-04-2010, 09:32 PM   #13
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Sounds like secondary ignition, either plugs or plug wires. It may be the coil, but plugs and/or plug wires are much more likely. If the plugs are relatively new, continue closing their gap. You may need to go as low as .020". If the plugs show any sign of wear, go ahead and replace them and gap them down before installation. If that does not do it, then replace your plug wires. Coils should be the last thing on your list.

If you have access to an oscilloscope, it could make diagnosis faster.
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