A strange misfire - Ford Forums

kaboom10 · 05-21-2008, 15:57

Maybe I should have posted this here? I just got a strange misfire today. I had a fouled plug with my original plugs and drove it hard and that disappeared. This is a recent set of platinums that were installed. I also had a set of Accel COPs put in at the same time. Maybe have 2000 miles on everything. It doesn't throw a code yet but you can feel and hear one cylinder isn't up to snuff. It doesn't show on the vacuum guage as anything burnt like a valve. It's rather a steady reading with the idle RPM not varying more than 10 rpm either side of 580. To me it feels like something on the verge of quitting functioning. Any ideas?

gmaier · 05-22-2008, 05:26

i can't remember if this engine has coil packs or not but if it does i would look at that

kaboom10 · 05-22-2008, 11:35

It's got COPs but it winds up without a perceivable miss. Only feel it at idle and under accelleration. Gotta check for a vacuum leak. I installed the vacuum guage and maybe screwed something up?

kaboom10 · 05-28-2008, 13:18

I found the problem finally. It was #3 COP. I took resistance readings from the contact point spring for the spark plug to either of the input terminals. Accel is a reading of 6.3 on the 200k scale and compared to a stocker of 5.2-5.6. The third coil I replaced read 4.3 and I figured that was the culprit before I started the engine to try it. This reading confirms why it wasn't a complete misfire. I'm just still used to complete misfires from single coil setups. I'm not at all a chebie fan but the coil per cylinder setup is ez as far as troubleshooting. Thanx to all for the inputs.