92 Chevy Knocking and Idling very rough


Old 04-30-04, 01:24 PM
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92 Chevy Knocking and Idling very rough

I have a 92 chevy c1500 truck with a 350 engine 145k miles. A couple of days ago it started knocking loudly when I accelerated. Never at idle just under acceleration or while going uphill. When I really put it to the floor the knock mostly goes away. Also it idles very rough but smooths out as soon as I give it a little gas.

A mechanic replaced the EGR Valve and put new plugs in it. The knocking is a lot quieter than it was but it's still noticeable both when engine is hot or cold. Idle is still very rough. He thinks that it is a timing problem of some sort.

I'm not a mechanic but I ran the diagnostic by grounding the diagnostic terminal and I'm getting a code 13 (Oxygen sensor fault). The check engine light comes on periodically when I'm driving around and has long before the knocking and idling problems.

I'm going to replace the dist. cap and rotor today for no other reason than they're probably due anyway.

Any ideas?
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Old 04-30-04, 04:45 PM
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Location: Boynton Beach Florida
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I would check the fuel pressure. With that code, you may have a lean situation. You really need a scanner so as to look at all of the data for problems.
Old 04-30-04, 05:01 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
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If the knock is real loud it may be a connecting rod at that mileage.
Old 04-30-04, 09:52 PM
mike from nj
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Originally Posted by davo
If the knock is real loud it may be a connecting rod at that mileage.
especially with a chevrolet

((((just joking))))

might also be a carbon buildup on the piston tops, might want to try a decarbonizing spray from GM. although this noise comes on more gradual.

also, if you can reproduce the noise by revving it in neutral, sometimes pulling off one plug wire at a time will tell you which cylinder is making the noise(provided it is an engine noise)

if the noise is a timing problem, you can set the timing back for a while and see if the noise goes away

you might have two problems, the one for the code and one for the noise.

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