Throttle popping from one cylinder why do the gods mock me so?

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brianwrites - 23 Jan 2007 04:13 GMT

Why do the truck gods mock me so? I've got a 93 chevy 1500 350 5.7 tbi.
I got a used engine, not rebuilt but used. This is the third engine
the truck has had. Wife has a lead foot, but more on that later.
Started the engine, sounded strong, oil pressure jumped up to 30 psi as
soon as it started.

Check engine light came on. Then popping through throttle body. Read
alot about timing. Adjusting the timing to TDC as specified in the
Chilton's manual. Popping still heard in the throttle. New plugs, new
wires. With the engine running, I removed then replaced the wires from
the distributor. When I got to number five and removed the number five
wire from the dizzy, the throttle backfire stopped completely. I have
little to no power when I try to drive the truck and my oil pressure
dropped back down to danger zone after I let it idle for about 10
minutes. Should I whip out my compression gauge or should I whip out my
baseball bat and try to get the money back from the guy that sold me
the crap engine?

Any advice would be great.

Brian
1993 Chevy 1500
"My Daddy gave me that there truck"

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KjunRaven - 26 Jan 2007 00:48 GMT

"brianwrites" <be@brianwrites.com> wrote in news:1169525611.435794.115090
@v45g2000cwv.googlegroups.com:

> Why do the truck gods mock me so? I've got a 93 chevy 1500 350 5.7 tbi.
> I got a used engine, not rebuilt but used. This is the third engine
[quoted text clipped - 19 lines]
> 1993 Chevy 1500
> "My Daddy gave me that there truck"

as already mentioned in the only reply that wasnt lame.........sounds like
a cam lobe not lobeing anymore.....if you remove the valve cover from the
offending bank and turn it over with starter (ign. coil disabled) you will
be able to see lack of lift on offending valve.......BTW: WTF is a 'dizzy'?

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Whitelightning - 26 Jan 2007 01:14 GMT

> as already mentioned in the only reply that wasnt lame.........sounds like
> a cam lobe not lobeing anymore.....if you remove the valve cover from the
> offending bank and turn it over with starter (ign. coil disabled) you will
> be able to see lack of lift on offending valve.......BTW: WTF is a 'dizzy'?

I figured dizzy was the distributor.
As to the popping there is another possibility here. Used engine sat how
long?
There could be an intake valve stuck partially open Have run into
that a time or two before with used engines that have been sitting for
sometime.
Pull the valve cover off the left bank, number five cylinder is third back
on that side, the intake valve will be the third from the rear of the head.
watch its movement, look for its valve spring to be partially compressed,
also look for a broken valve spring.
If it appears to be a stuck valve, pull the plug, bring that piston to top
dead center, fill the cylinder with marvel, soak the valve stem with marvel
mystery oil, let sit over night. with the plug out, turn the engine over to
blow marvel out of cylinder and see if the valve freed up. if it didn't,
Pull rocker arm off, and lightly rap the valve stem with a small hammer.
Make sure you hit the stem square or you could dislodge the valve spring
keepers

Of more concern is the low oil pressure. that sounds like worn main
bearings.

Whitelightning

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brianwrites - 29 Jan 2007 14:43 GMT

So, I pulled the valve cover and the rocker for the # 7 cylinder was
completely loose and I'm positive that I adjusted it properly before
installation. The push rod for the # 7 exhaust valve is completely
loose even after tightening the valve all the down until it bottoms
out. This sort of leads me to believe that the lobe is collapses. But
I also look into the lifter valley and could see the the lifter
doesn't seem to be sitting at a proper height compared to the others.

On another notes. I adjusted the timing and after each adjustment, the
next time I start it, it jumps time. Is the ECM gone? Or perhaps a bad
ignition moudule.

Did a compression test and everything checked out fine.

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