Engine Backfire

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mistermister - 19 Jul 2005 01:13 GMT

Need Help diagnosing unusual problem. 95 Mustang 3.8 (6cyl) began misfiring
on cyl 3. Mechanic said probably electrical. Replaced ignition module,
spark plug, and wire. Still bacfires. Replaced fuel injector. Same thing.
With plenum and throttle body off, compression testor installed in #3,
ignition disabled, and fuel injector un-plugged I turned the started and
backfire still occurs (compression was 150lbs) up through intake manifold.
I even stuffed a rag in #3 intake port and the rag blew out during engine
turn over. What can this be? Any ideas?

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Backyard Mechanic - 19 Jul 2005 01:45 GMT

> Need Help diagnosing unusual problem. 95 Mustang 3.8 (6cyl) began
> misfiring on cyl 3. Mechanic said probably electrical. Replaced
[quoted text clipped - 5 lines]
> intake port and the rag blew out during engine turn over. What can
> this be? Any ideas?

disable the spark on cyl 2... bet it doesnt backfire anymore

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Fred V. - 19 Jul 2005 01:46 GMT

Hi

You cannot backfire when doing a compression test because all the plugs are
out and the tester is in the
cyl under test. Check all the cylinders and tell us the
readings.

Fred

> Need Help diagnosing unusual problem. 95 Mustang 3.8 (6cyl) began
> misfiring
[quoted text clipped - 5 lines]
> I even stuffed a rag in #3 intake port and the rag blew out during engine
> turn over. What can this be? Any ideas?

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Big Al - 19 Jul 2005 04:16 GMT

> Hi
>
[quoted text clipped - 4 lines]
>
> Fred

Back in the 60's a friend of mine had a 59 Pontiac with a 389 in it. Had a
bunch of stuff done to the engine including 13.5 to 1 pistons. We were
trying to do a hot compression test and it fired and broke the compression
tester. I was holding the gauge and fire shot out of the hole:) All we could
figure was it pre-ignited. All plugs were out and the ignition was off.
About two weeks later we pulled the pan and all the rod bearing were down to
copper. Had about 500 miles on it. So we pulled it down and went to 10.5 to
1's. Solved the problems.

Al

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