Jeep Misfire problem

[SMLEshooter]

Latest update:

Looks like no burnt valves. Removing the rockers and spinning the valves revealed them to be smooth as butter with no grittiness, so they don't seem to have any carbon buildup.

The valve springs look good.

Cylinder rings appear to be good as well after a wet compression test.

Put it back together and now my compression is back up to 60 from zero...

Any ideas?

 

[SMLEshooter]

Well, it looks like the number one piston rod may be bent.

It does not appear to be coming up as high as the other pistons.

Anybody else ever experience that?

 

[georgia357]

I guess it's possible if water got in the cylinder. Looks like you should see signs of water if that was the case.

 

[harrycalahan]

How are you checking for a burnt valve? Are you applying air to the cylinder with it at TDC? You can't visibly see a burnt valve by taking the valve cover off. I really doubt you have a bent rod. Unless at one time or another you had large amounts of coolant leaking into the cylinder when parked. Diagnosing compression loss is simple if you have the tools and experience. By the sound of it, you're in a little over your head. May be time to take it to someone with some know how.

 

[roundhouse]

how are you deciding that one piston doesnt come up as much as the rest?

 

[SMLEshooter]

How are you checking for a burnt valve? Are you applying air to the cylinder with it at TDC? You can't visibly see a burnt valve by taking the valve cover off. I really doubt you have a bent rod. Unless at one time or another you had large amounts of coolant leaking into the cylinder when parked. Diagnosing compression loss is simple if you have the tools and experience. By the sound of it, you're in a little over your head. May be time to take it to someone with some know how.

Well, I did take it to a local 4x4 repair shop yesterday after I gave up.

He did a leak down test and determined that the cylinder does not have any leak down. It holds compression when air is applied and there does not seem to be any leakage out the exhaust.

how are you deciding that one piston doesnt come up as much as the rest?

Ran the first cylinder to TDC and measured it to a fixed point. Then ran cylinder two to TDC and measured it to the same fixed point.

Personally, I am having a hard time believing it's a bent connecting rod, but all the other tests seem to indicate they're good.

 

[SMLEshooter]

By the sound of it, you're in a little over your head. May be time to take it to someone with some know how.

Is that an offer??

McDonough isn't that far from me...

 

[galvatron]

This makes no sense. .....
Your #1 cylinder had 0 psi for compression, the other 5 ran in the 160-170 range...
Did you pull the head? What did you do or have done to get the compression to 60psi from zero? If spinning valves by hand upped your compression, I'd start there. A leak down test would scream here's the problem if that's true.
What fixed point was used to measure the piston height? Was it from the cylinder block deck with the head removed?
Not buying the bent connecting rod theory if you went from 0 to 60psi by turning valves by hand.

 

[wirepuller]

My guess is TPS throttle position sensor
I got a 92 explorer 4x4 , free , would run but quite poorly.
Codes were Map voltage / O2 sensors left bank bad / A/C relay issues
I went to the junk yard got a Map / AIC / TPS for 30.00 bucks . New would have been a couple $$$
I replaced the ones on the motor checked the connections on the O2 sensors ran a can of Sea-foam thru it ......
It runs GREAT.! 129k on it now

Bottom line is if you are going to be a mechanic start at the junk yard, Way cheaper parts.

 

[harrycalahan]

Is that an offer??

McDonough isn't that far from me...

I normally would but Im covered up right now. Heres the thing...your updates are conflicting. Maybe its miscommunication between you and the mechanic, I dont know. Do this, take all the spark plugs out. Rent you a compression gauge from auto zone and check each cylinder by turning the engine over with the starter for the same duration (5 seconds each). Write down each psi reading and see what you have. Each cylinder should be within 10% of the highest reading. You should get a reading between 130-150 psi. If your highest reading is 150, the lowest another cylinder can read is 135 generally speaking. Do everything the same and get a baseline to work from.