Ignition Problem
Ignition Problem
I have a 94 EVO that I just started having a problem with. The front cylinder is misfiring when it's first started and then it settels out and rund great with it's warm. It's only the fron cylinder and only cold. I've switched the plug wires around, put new plugs in, put new wires on, and NOTHING changed this. It's always the front cylinder. Any ideas????
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Joined: Aug 2007
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From: NW AR
Burnt exhaust valve?
Is the front plug significantly darker in color than the rear? Is it wet with gas or oil? Check the compression when it is cold and when it is warm. Leak down test when cold. Just tossing out ideas.
Is the front plug significantly darker in color than the rear? Is it wet with gas or oil? Check the compression when it is cold and when it is warm. Leak down test when cold. Just tossing out ideas.
Thanks Dr. Hess,
I'm not too sure that's it. And this is why I think that. I just had the motor apart and put 10.5:1 Kieth Black pistons in. and tested the compression. It's steady and strong at 175psi.
I also forgot to mention that I tested the spark using my timing light. On the back cylinder it's steady. The front cylinder is not. So I'm thinking it's an electrical problem
I'm not too sure that's it. And this is why I think that. I just had the motor apart and put 10.5:1 Kieth Black pistons in. and tested the compression. It's steady and strong at 175psi.
I also forgot to mention that I tested the spark using my timing light. On the back cylinder it's steady. The front cylinder is not. So I'm thinking it's an electrical problem
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
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From: Bluffton, South Carolina
What type of ighition do you have???
If you have an after market, perhaps the trigger wire to the front coil is loose or has an intermitent connection or the coil is going bad on that side.
John
If you have an after market, perhaps the trigger wire to the front coil is loose or has an intermitent connection or the coil is going bad on that side.
John
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Joined: Mar 2007
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From: TOAK western branch
Sounds most plausible. Although id do the comp tests. To confirm weak coil id swap the input wires to the coil so the one for the front fires the rear and such. Eliminates the coil or confirms.
As far as I know the ignition is stock, but i do have the Screaming Eagle module under the seat. I was thinking the coil might be going bad but didn't know if it would effect both cylinders...
I will do that. and see what happens thanks.
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Elite HDF Member
Joined: Sep 2007
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From: Bluffton, South Carolina
OP stated he already switched wires around and replaced them. Compression/leakdown test is a good idea too.
John
John
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Seasoned HDF Member
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From: TOAK western branch
He did the plug wires not the imput wires to the coil. He only confirmed the plug wires are good not the coil to the front cyl.
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
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From: Bluffton, South Carolina
Screaming Eagle ignition module fires both cylinders at the same time. So either no/low compression or bad coil. The pick up could be going but this is very rare when it starts on one side first, but it can happen.
John
John
Last edited by miacycles; Jun 17, 2012 at 04:17 PM.