Low compression on one cylinder

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Mar 9, 2012
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Well going through this little 2.3 on my 96 ranger. I had a slightly rough idle I couldn't seem to get out of it. Well compression on cylinder 1 is 124. The rest are 160-165. My guess is something happened to make that one cylinder low. What would you do with it? Just run it as is? I wonder how long it can operate as is? Swap a used engine... The truck is relatively solid but not in the best shape plenty of dents. And scratches, mostly superficial stuff undercarriage and what not isn't to rusty. Check out the cylinder wall pictures below. Tell me what you think.
 

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Run it. Compression will rise as that stuff wears down and you can get another 100,000 miles out of it.
Any idea what that "stuff" is the engine was a junk yard engine has about 150,000 miles on it
 
It's a 96, not worth much, run it. Likely will go longer than you think.

No additive is going to add metal back to where it wore off. Use the money for a heavier oil instead.
 
Junk yard engine...kind of looks like while it sat maybe rust formed on the piston walls, and then when it was started a little scraping went on and did a little damage? It looks like there is some pitting of the metal on the those walls. When engines sit for a long time the moisture can really do some damage, looks like that is what happened, but who knows?
 
If the worst problem is a slightly rough idle, why do anything? Just run it.

Might get better. Might get worse. Might run a long time with only a "slightly rough idle". No-one can say.
 
You could try some form of piston and ring wash. Berrymans B12 does a pretty good job of unsticking rings and dissolving carbon. Then use the engine hard, to help re-seat the rings.
 
You could try some form of piston and ring wash. Berrymans B12 does a pretty good job of unsticking rings and dissolving carbon. Then use the engine hard, to help re-seat the rings.
Would you do a piston soak I guess?
 
There's plenty of other things that can contribute to a rough idle, too. I wouldn't assume it's just due to compression. Idle air control valve, EGR valve malfunction, vacuum leak, cracked insulator on a plug, etc.

Does it have any codes?
 
I'd just run it. I think it will be fine and probably even clean up some over time. Sounds like the truck doesn't owe you a thing.

just my $0.02
 
There's plenty of other things that can contribute to a rough idle, too. I wouldn't assume it's just due to compression. Idle air control valve, EGR valve malfunction, vacuum leak, cracked insulator on a plug, etc.

Does it have any codes?
No codes plugs are new, Iacv is new as is the tps sensor. EGR valve tests good when applying vacuum.
 
Performed the test again warm . Cylinder 1 was 130 dry compression test wet it went up to 143. I don't feel like that's a significant change possibly pointing towards a valve issue vs a ring issue? The rest of the cylinders were around 165-170 dry
 
I wish I could see the valves without removing the head to see what's going on with them.
 
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