Uneven compression

[renton]

My 05 Ranger with 3.0 has had good compression results in all cylinders except #2 which is lower at 120psi. Rest are around 150 or 160. It's been this way since I got the truck 6 years ago and haven't gotten worse. Vacuum gauge reads normal and no codes. If this was burned exhaust valve wouldn't my vacuum gauge flicker up and down? It also hasn't gotten worse in 6 years which seems odd for valve. I'm leaning towards worn rings in there causing slightly lower compression. What do you think. It's ok except my idle is always rough.

 

[RonD]

Could be recessed exhaust valve seat in #2, there was a TSB for 2004-2006 Ranger 3.0ls

Just hasn't gotten worse, which is odd
You can add a teaspoon of oil after another dry test(assuming 120psi again), if test shows 150psi after adding the oil then yes that confirms worn rings, if it just comes up to 130-140 then its a valve leaking

Any cylinder will go up when you add oil, its how much it changes that will tell you if its rings or valves

Could also be a worn push rod or rocker, so intake valve is opening late so less air to compress

 

[Fast Eddie]

My 05 Ranger with 3.0 has had good compression results in all cylinders except #2 which is lower at 120psi. Rest are around 150 or 160. It's been this way since I got the truck 6 years ago and haven't gotten worse. Vacuum gauge reads normal and no codes. If this was burned exhaust valve wouldn't my vacuum gauge flicker up and down? It also hasn't gotten worse in 6 years which seems odd for valve. I'm leaning towards worn rings in there causing slightly lower compression. What do you think. It's ok except my idle is always rough.

A leak-down test will verify if it's valves/rings. If you tear down the motor to replace rings (or get it from the top), check for a bent rod. A shorter compression stroke could have a similar affect. Just not sure about 30-40lb difference unless it's a combination of both.

 

[renton]

Yeah I read about recessed exhaust valve but I assumed after this long it would get worse. I wish I had access to leak down tester

 

[Dirtman]

Just do a wet test. If compression rises it's possibly a ring ring issue, if it doesn't change much it's a valve issue.

 

[renton]

Just do a wet test. If compression rises it's possibly a ring ring issue, if it doesn't change much it's a valve issue.

I know if its rings products like engine restore can boost compression a bit but there's nothing to help valves is there?

 

[Blmpkn]

I know if its rings products like engine restore can boost compression a bit but there's nothing to help valves is there?

Most of those products are snake oil.

I hadn't heard of engine restore though, so I googled it. First review sounds awesome lol.

 

[Dirtman]

I know if its rings products like engine restore can boost compression a bit but there's nothing to help valves is there?

Nothing from a bottle can fix worn rings or cylinders. Well I mean if you drink a bottle of moonshine you won't care about the rings being bad anymore...

Valves are easier to fix than rings though since you can just take the heads off and not pull the whole engine.

 

[renton]

Most of those products are snake oil.

I hadn't heard of engine restore though, so I googled it. First review sounds awesome lol.

View attachment 64488

Our company has used it in a few old work trucks with good results. These were old V8 not a high tech BMW engine.

 

[Dirtman]

Our company has used it in a few old work trucks with good results. These were old V8 not a high tech BMW engine.

Sometimes just using super thick oil can mask the issue but it doesn't fix anything. I suspect that Is all engine restore is. There's no magic liquid that can actually fix worn metal, but a super heavy sticky oil will help temporarily seal the rings better. If the rings are bad you are on borrowed time no matter what you dump in...

 

[renton]

so added oil the cylinder and compression went from 120 to 150. Odd the other cylinders have good compression. My old truck had low on all of them, around 90psi but ran smooth.

 

[Snoranger]

Nothing from a bottle can fix worn rings or cylinders. Well I mean if you drink a bottle of moonshine you won't care about the rings being bad anymore...

Valves are easier to fix than rings though since you can just take the heads off and not pull the whole engine.

I have a 5 gallon water bottle full of quarters. That should be somewhere around $5000...

Tell me again how nothing from a bottle can fix worn rings.

Seriously though, a leak down test will point you in the right direction. If you don’t own a tester, you may be able to rent/borrow one from an auto parts store.

 

[Curious Hound]

I have a 5 gallon water bottle full of quarters. That should be somewhere around $5000...

Tell me again how nothing from a bottle can fix worn rings.

That's cheating

 

[Snoranger]

That's cheating

I don’t make the rules... I just exploit the loopholes.

 

[Dirtman]

I don't think pouring a bunch of quarters into an engine will solve anything!