1994 Chevy S-10 backfires through exhaust

KEVIN MILES

MEMBER
1994 CHEVROLET S-10
6 CYL
2WD
AUTOMATIC
500 MILES

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?

3 Replies

BUDDYCRAIGG

MECHANIC
2,262 POSTS

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.

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Saturday, August 1st, 2009 AT 7:32 PM

KEVIN MILES

MEMBER
2 POSTS

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

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Thursday, August 6th, 2009 AT 3:08 PM

BUDDYCRAIGG

MECHANIC
2,262 POSTS

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.

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Thursday, August 6th, 2009 AT 6:38 PM