My 1996 2.3 ranger has a slightly rough idle. No codes. Plugs, wires, coils etc are all new. Truck runs pretty strong overall not down on power. However when performing a warm compression test cylinder 1 was 130. The rest were around 165-170. When I squirted some oil in that cylinder it only went to 143. I assume this means it has a valve issue. Is there a way to see what's going on without removing the head? I have a boroscope . Only symptom I have is sometimes a minor stutter while idling. Any help is appreciated

 

Assuming engine cooling system is not blowing out coolant or tailpipe is putting out white smoke...................
i.e. bad head gasket seal on #1

Its a burnt exhaust valve 99% of the time, other 1% is "tulipped" intake valve
So head would have to come off either way

You can do "the dollar bill test" at the tail pipe to see if its a burnt exhaust valve

Or a Leakdown test, to see which valve is leaking

But again, head has to come off regardless, so the knowledge of which valve is leaking would not really help anything

Once head is off, put it upside down, stabilize it, all spark plugs in
Fill each cylinder cavity with water, wait
See which ports have water leaking out

But with head off I would do a valve job on all 4 cylinders

 

[QUOTE=RonD;2210500]Assuming engine cooling system is not blowing out coolant or tailpipe is putting out white smoke...................
i.e. bad head gasket seal on #1

Its a burnt exhaust valve 99% of the time, other 1% is "tulipped" intake valve
So head would have to come off either way

You can do "the dollar bill test" at the tail pipe to see if its a burnt exhaust valve

Or a Leakdown test, to see which valve is leaking

But again, head has to come off regardless, so the knowledge of which valve is leaking would not really help anything

Once head is off, put it upside down, stabilize it, all spark plugs in
Fill each cylinder cavity with water, wait
See which ports have water leaking out

But with head off I would do a valve job on all 4 cylinders[/QUOTE


No smoke of any kind cooling system holds pressure as well. No noticable oil burning either. I'll try the dollar bill test in the morning. The head probably isn't that hard to pull all things considered. Basically with the dollar bill test is if it get sucked inward at all the valve is burned?

 

Yes, tail pipe should have a steady outward flow
A misfire will be a hesitation in outward flow, so the bill/paper doesn't get pushed as far out
Burnt exhaust valve pulls exhaust IN when #1`is on its intake stroke, so bill/paper moves toward tail pipe, gets sucked back

If you have another vehicle with no misfires do the test on it as well to see the difference

 

I will do that first thing tomorrow I'll probably video it as well and share it here. Thank you for the help thus far

 

Here is the dollar bill test video. Thoughts?

 

Yup, burnt/leaking exhaust valve
You can see/hear when bill gets sucked in and hits tail pipe

 

Anything in particular that causes that? How long can it live like that?

 

Burnt exhaust valves are just part of having an ICE(internal combustion engine) that uses Valves

Intake valves get HOT but are cooled by incoming air/fuel mix
Exhaust valves just get HOT, lol
The valves rotate each time they are opened
Valves are cooled by their contact with the Valve Seats which are cooled by the head's coolant passages
So the lap angles, surface contact between valves and valve seats, are important, they need to be wide enough to transfer as much heat as possible when valve is closed
Valves are closed 75% of the time in a 4 stroke engine, each only opens on 1 stroke of the 4 stroke cycle

There are a number of reasons exhaust valves stop sealing
Valve doesn't rotate evenly so develops a HOT SPOT
Lean condition in a cylinder, pinging/knocking, causes pitting and higher heat levels in the one cylinder
Exhaust valve can warp a bit with high heat so doesn't seal as it rotates, this allows HOT exhaust gases, during firing, to escape thru the gap, which eats away at the metal valve edge and metal valve seat, then it just gets worse and worse as the HOT gases continue to escape, and eats away more and more of the metal thru the ever increasing gap

You can run engine this way, it will just lose more and more compression until you have a steady misfire at any RPM
There is no way to slow it or to prevent it from ever happening

In the "olden days", lol, valve jobs were common at 60k miles, and rings and bearings at 100k miles
Newer materials for valves and seats have extended that to 240k+ miles, rings and bearing can do 400k+ miles, so 4 fold increase
But exhaust valves still burn on any ICE that uses valves, and it can happen at anytime

 

I've read that carbon build up can cause this to. Probably a long shot but would you try a induction service with seafoam or something similar? The engine did come from a junkyard has 150,000 miles.

 

Carbon build up retains heat in the cylinder and it also increases compression ratio, a double whammy, so yes, the extra heat can cause it, exhaust valve runs hotter and retains more heat
There is no fix, except for replacing leaking valves

Running a can of seafoam in the gas tank once a year can help prevent, and clean up, any carbon build up
And with seafoam in the tank do a Texas Tuned up, run engine on the highway as fast as possible to loosen up and blow out any carbon, lol

Dumping a liquid into a running engine can cause more issues than it cures, but up to you

As said, once the exhaust valve is leaking it will just get worse, can't slow it down or stop it

 

Yeah fair enough. Wonder how many hours it takes to pull the head.

 

Google: replace head gasket 2.3l lima engine

A shop would charge 8 hours to remove and replace a 4cyl SOHC engine head, but could be done in 6 hours, depending on tools you have and experience

Take LOTS of pictures during disassembly, they are free, and you WILL NOT REMEMBER where that hose/wire goes, lol

You can see what a rebuilt head goes for, its an exchange so you pay a Core Deposit, they ship you the rebuilt head, you swap it out and send them back your head(for refund of deposit) so it can be rebuilt and sold to someone else, get pricing

Then call local Machine Shops, ask them about cost of valve job for your 2.3l SOHC engine head, AND lead time, might take a week to two weeks to get it back, it will be cheaper, but also takes more time
Then YOU make the decision

 

took the plug out tonight and looked into the cylinder again with my boroscope. I saw this!! I was pretty sure it was coolant but I wanted to be sure. I hooked shop air to the cylinder and then my coolant pressure tester to the radiator. I could make the pressure tester rise by pumping air into the cylinder from my compressor. Ok pretty definitive. So then I unscrew the air from the cylinder and do the pressure test for the cooling system and it held strong for 10 minutes. So then I put it all back together and I did a block test the damn truck passes a block test. It doesn't smoke and there's no coolant in the oil or oil in the coolant. So clearly there is coolant getting into the cylinder I can even see rust and pitting in the cylinder wall from this issue. However no other symptoms except the slightly low compression. I didn't get any leaking from the valves either. Crazy!!! Has anyone ever seen a 2.3 Lima do this? Just seems odd.

 

That is pretty bizarre
Bad head gasket or cracked head would be the only way air pressure in spark plug hole could cause radiator pressure to increase

Yet cooling system held pressure with spark plug hole open?

Not a fan of Block tests, lol

You can put cooling system pressure tester back on, pump it up to say 10psi
Then crank engine over, no start, and see if the pressure goes up and down as #1 is on compression stroke, called Glove or Balloon test, as either will inflate and deflate if pressure from a cylinder is leaking into cooling system

 

I did try that and it didn't change. It seems to only leak into the cylinder when it's cold and sitting for awhile......weird!!

 

Is there any coolant or anyway for air from the intake to get into the cooling system. Coolant pressure test doesn't leak down. However applying shop air to the cylinder does move the coolant in the radiator. I retested it today and I did get a little air out of the intake valve when. Applying air to the combustion chamber. The exhaust valve sealed well though.