1994 Chevy S-10 backfires through exhaust

1994 CHEVROLET S-10
500 MILES • 6 CYL • 2WD • AUTOMATIC
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KEVIN MILES
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Just replaced the engine, 4.3 L V6, ("W" engine code).
Everything about this engine is running great, except, drive it down the road for 30+ miles on the interstate and it falls on its face and starts to backfire through the exhaust.
temp guage - 210 - 220 deg.
oil pressure - 70 -80 psi
no check engine light or codes
allow it to set for 20 minutes and your good for another 30 miles and then it re-occurs.

Also, is the oil pressure to high ?
Aug 1, 2009 at 11:13 AM
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BUDDYCRAIGG
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what you are describing at first sounds like a failing ignition module.
But...
they normally take longer to cool back down, and they don't cause a backfire.

and yes, your oil pressure is too high,
hook up a mechanical gauge to verify that the dash gauge is reading correctly.
Aug 1, 2009 at 7:32 PM
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KEVIN MILES
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Tell buddy he was right !!! I believe that the backfire was caused by
unburned fuel reaching the cat.converter.
Thanks so much,
Kevin in Oklahoma City,

PS: What can cause high oil pressure in a new engine,( Marshal Engines
provided the new pump), will it lower with use and wear, or how can it be
lowered ??

Thanks again
Aug 6, 2009 at 3:08 PM
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BUDDYCRAIGG
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so you replaced the module and it's running like it should?

did you verify that the pressure is really that high with a manual gauge?

They may have sold you a high pressure pump.
The pressure control valve may be stuck
Or worst case, one of the bearings for the cam or crank was installed incorrectly and the oil feed holes are not lined up.
Aug 6, 2009 at 6:38 PM