A friend just bought a '92 F150 with a 5.0 V8 only to find it has bad compression on #1 cylinder. The other 7 cylinders are fine. I think he said the plug was blackened and the compression reading was around 50 psi. Various shops say it could be ring or a burnt valve and quote anywhere from $1500 for that to several thousand for replacing the engine. He is more inclined to just drive it as it is. Any suggestions, comments, etc would be appreciated. Thanks
Low Compression, One Cylinder, What to Do?
- Thread starter TallPaul
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I would recommend a wet and dry compression test to determine if it is rings or valve leakage or use a leakdown tester to get better info to decide whether to do valve job or engine and run a complete compression test to determine other cylinders overall condition. What does it sound and look like inside? How many miles on engine and does the friend plan on keeping it?
RX it as Aaron Ber did on his low compression engine. Loook in Fuels Additives Cleaners at Aarons Auto-Rx website.
Cheers..s
Cheers..s
Wet dry test sounds like a great idea.
His mech did all cylinders. Don't know the psi, but said the other 7 were fine. Truck looks great and he said the engine sounds fine. He plans to keep it.
Also like the idea of hotter plug if he decides to leave it as is. AutoRx, thinks so? Maybe a stuck ring? Could free up and get some better compression. He is out today, so I will have to wait to ask him any more questions.
His mech did all cylinders. Don't know the psi, but said the other 7 were fine. Truck looks great and he said the engine sounds fine. He plans to keep it.
Also like the idea of hotter plug if he decides to leave it as is. AutoRx, thinks so? Maybe a stuck ring? Could free up and get some better compression. He is out today, so I will have to wait to ask him any more questions.
I would check the valve clearance as well, make sure there IS a clearance
AutoRX restored compression on Cyl#3 from low 140s to high 160s pretty much in the first clean cycle. This was at 125k miles on a 99 Civic (D16Y8). With 171k miles now and it is consistent 165-175psi across all 4.
AutoRX restored compression on Cyl#3 from low 140s to high 160s pretty much in the first clean cycle. This was at 125k miles on a 99 Civic (D16Y8). With 171k miles now and it is consistent 165-175psi across all 4.
I don't think he wants to spend the money. Truck has 129,000 miles and cost him around $1500. He had said that it ran smoothly, which is somewhat puzzling because I was told if one cylinder was bad on compression it would show up in a rough running engine. We'll have him reevaluat that. Also possible his mechanic flubbed the comp test on that cylinder and it is not quite so bad. Definietly deposts on that plug though and the other plugs looked fine.
Maybe that cylinder runs hotter for various reasons (leaner as on end, water jacket inadequate in that area, bad plug wire, etc.) and the ring gummed up only on that one cyl. Definitely some solvent or AutoRx to help free ring would be worth a shot. Do all the low cost, can't hurt/may help things first. Can always spend the bucks later if not satisfied.
Don't know oil consumption as he only got the truck this Monday. Does not blow blue smoke anyway, so it is not a fogger.
Thanks, keep the ideas/thoughts coming. Paul
Maybe that cylinder runs hotter for various reasons (leaner as on end, water jacket inadequate in that area, bad plug wire, etc.) and the ring gummed up only on that one cyl. Definitely some solvent or AutoRx to help free ring would be worth a shot. Do all the low cost, can't hurt/may help things first. Can always spend the bucks later if not satisfied.
Don't know oil consumption as he only got the truck this Monday. Does not blow blue smoke anyway, so it is not a fogger.
Thanks, keep the ideas/thoughts coming. Paul
If there is low compression and an oil-fouled plug, it's probably a broken ring/worn out engine. It will probably use more oil on a highway trip than around town if that's what's wrong.
Not sure what the plug looked like. He should pull it and see for himself. Then put a new plug in and check in 500 miles. We'll have to figure out the oil consumption etc. I told him to have the mech test the oil pressure and the mech told him he could do it himself with the dash gauge. Mech apparently doesn't know the dash gauge is dummy and will only report severe low pressure.
If you're able to pressurise the the suspected cylinder with air, bring that cylinder up to /TDC Compression/ and listen to the tail pipe; if you hear hissing, it's a burnt valve.
With the old type compression gauges, you would squirt some motor oil on top of the piston and take a reading; if the compression goes up a little bit, that's an indication of worn piston rings.
With the old type compression gauges, you would squirt some motor oil on top of the piston and take a reading; if the compression goes up a little bit, that's an indication of worn piston rings.
You may have a carboned up ring pack. Stuck rings burn oil and leak, even though if they were clean and free they would be serviceable.
An Auto Rx treatment may be worth considering.
I'd get a leakdown test, first.. you'd know if it's a valve or bore problem.
An Auto Rx treatment may be worth considering.
I'd get a leakdown test, first.. you'd know if it's a valve or bore problem.
Run it 'till she blows!
He wants to try Auto-Rx. Anybody remember the discount code for Auto-Rx? I recall Frank recently posted it.
ARXFQ
Is one. Don't know if there are others.
Is one. Don't know if there are others.
ARXBITOG is another, but ARXFQ gives a bigger discount.
Thanks, I passed the info on.
I have a 92 F-150 w/ about 137k on it. I got it from my Grandfather w/ 125k about one year ago. It has dealer 3k dino changes all its life, so I didn't think it would be in bad shape... However it did have a rear-main oil leak and I wanted to try AutoRX. I am 500 miles from completing the rinse phase and starting a 2nd treatment. So far, the rear main leak seems to have stopped, or at least slowed down allot... Also, seat of pants tells me there is more power and the engine seems to turn over a bit easier.
I suspect the AutoRX has cleaned up some ring deposits and increase compression. I have no pics or compression numbers to support this however...
I would give it a try. It seems to have made a big difference on my 92 302 engine...
I suspect the AutoRX has cleaned up some ring deposits and increase compression. I have no pics or compression numbers to support this however...
I would give it a try. It seems to have made a big difference on my 92 302 engine...
He's ordering two bottles. I'll post back how he liked it when finished. May take a while.
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