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engine missfires
#1
ok I am getting some backfires through the exhaust. it seems to be a misfiring cylinder.I have an exhaust leak at the headers on the same side was wondering if that could cause the misfiring .the spark plug was black when I took it out.I thought I had a bad spark plug I changed it and it fixed the problem 3 days later it started again.Could all this be caused by an exhaust leak in the header.

Eric


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#2
Check to see if it burned your wire to that cylinder. Dont believe the leak is the cause of the fouling plug but it may be related (burned wire or heating it up) If not check and make sure that plug wire is seating properly at the cap and the plug end.
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#3
Yes a header leak can cause a "backfire"

What's happening is the header leak is also an air leak. The air in the exhaust is causing un-burned fuel to combust.

Jeff T.

Low buck, touring style, '73 Convertible "rolling restoration", 351c, 2v heads with a shave and a haircut, Performer intake, Holley 650(ish), roller rockers, screw in studs, guideplates, stainless valves, Duraspark / Motorsports MSD, T-5 conversion. 1-1/8" front, 3/4" rear swaybars KYB shocks and some home brewed subframe connectors. Future plans; JGC steering box, Cobra brakes and... paint, interior, etc.

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passenger.

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#4
well I changed all the plugs and all of them where ok except the one by the header leak it was completely black so I will have to wait till I change the gaskets to see if that is my problem.But it's starting to look like it is there is exhaust soot on the spark plug wire.

And thanks for the reply's guys.

Eric


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#5
ok exhaust leak is gone but the backfires on that cylinder are still there.I changed all the spark plugs I put in hotter burning ones.I even rotated my distributor cap 180 degree's to see if the problem would switch to the other side.So now I have no clue what to look for anymore I switched the wire with one of my old ones same thing.Angry

Eric


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#6
Check that all 8 are firing take a timing light, hook it up with the engine running, and move the magnetic pickup to all 8 ignition wires, make sure all of them are firing in rhythm.

Next check your initial timing, make sure it has not changed.

Possiblly do a compression test on all 8 make sure the ones backfiring are not low.

If they are the valves may need to be tightened On those backfiring ones.
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#7
(09-12-2010, 03:13 PM)72HCODE Wrote: Check that all 8 are firing take a timing light, hook it up with the engine running, and move the magnetic pickup to all 8 ignition wires, make sure all of them are firing in rhythm.

Next check your initial timing, make sure it has not changed.

Possiblly do a compression test on all 8 make sure the ones backfiring are not low.

If they are the valves may need to be tightened On those backfiring ones.

thanks for the info I will try that

Eric


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#8
so I put the timing light on the #3 plug it was erratic as hell.It would fire really slow and then really fast just completely off. So I will put my old distributor back on. I wrote to petronix to see what they will do it's either the ignitor3 or the cap but this distributor is new, out of the box they better send some replacement parts.

Eric


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#9
Ok i heard bad things with our cars and the ignitor 3. Did you buy the petronixs distributor or is this a retrofit for a ford distributor?

i believe the PIII does not use the magnetic pickup like the older P1 and P2 so the trick of taking the magnetic sleeve out and rotating it one face on the distributor points cam and seeing if the misfire follows to the next plug won't work.

before you go too crazy moving things, replace the ignition wire on #3 and see if the same problem occurs. obviously if #3 still miss fires the P3 is messing up.

I had some major issues with my Petronix about 2 years ago i kept having the magnetic sleeves fail. I kepted a set of points in the car for a while but they kept drifting constantly, but that did tell me a lot of problems were with the petronixs and my ignition wires.

so before anything just try another ignition wire too make sure its possible to get a defective wire.

now if the car continues to miss fire i would then drop the other distributor in my money is on the car running fine with the points reinstalled, but go slow and see if you can narrow the issues down
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#10
(09-15-2010, 06:51 PM)72HCODE Wrote: Ok i heard bad things with our cars and the ignitor 3. Did you buy the petronixs distributor or is this a retrofit for a ford distributor?

i believe the PIII does not use the magnetic pickup like the older P1 and P2 so the trick of taking the magnetic sleeve out and rotating it one face on the distributor points cam and seeing if the misfire follows to the next plug won't work.

before you go too crazy moving things, replace the ignition wire on #3 and see if the same problem occurs. obviously if #3 still miss fires the P3 is messing up.

I had some major issues with my Petronix about 2 years ago i kept having the magnetic sleeves fail. I kepted a set of points in the car for a while but they kept drifting constantly, but that did tell me a lot of problems were with the petronixs and my ignition wires.

so before anything just try another ignition wire too make sure its possible to get a defective wire.

now if the car continues to miss fire i would then drop the other distributor in my money is on the car running fine with the points reinstalled, but go slow and see if you can narrow the issues down

I already tried a different wire it's not like it is just firing once in a while it seems to be firing randomly even at the same time as other cylinders.My old distributor has an ignitor 2 in it and it worked fine so I will put that in and wait to here from petronix.
and it was a new billet distributor from petronix straight out of the box

Eric


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