Engine Backfire

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?

"mistermister" > wrote in
lkaboutautos.com:

> 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?
>
>


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

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

"mistermister" > wrote in message
lkaboutautos.com...
> 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?
>

"Fred V." > wrote in message
m...
> 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
>

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