Turtle_XJ

So I've been trying figure out a gas in oil situation on my XJ. Its been having a little bit of a jumpy idle and my fuel pressure jumps on a gauge between 45-50psi. I've changed or clean every sensor i can think of, cleaned the throttle body, replaced the fuel pump and checked my injectors. The only codes I've been throwing are O2 sensor and lean fuel in bank 1. The O2 sensors threw a code before and after new sensors.All look and function like they should. I figured id do a compression test to see if my rings failed.
These are the reading:
#1-125psi
#2-125psi
#3-95psi
#4-130psi
#5-125psi
#6-125psi

I put some oil in the cylinder and compression on cylinder 3 came up to 110psi

So i guess i can assume the ring is bad in that cylinder but it still has 95psi dry and holds pressure after cranking. Do you think even though this ring isn't to bad yet it could still be causing gas in my oil? I cant think of anything else but I've had cars with much worse worn out rings and it hasn't been like this. It doesnt smoke but the exhaust smells rich and it has a high idle on start and goes down imediatly, like ther is already fuel in the clynders but the injectors hold pressure and dont leak.

Thanks.

1998 4.0 Auto 195000 miles

tedparis

95 pounds is sufficient from what I have learned and shouldn't allow be letting gas by the rings like that. How did you discover the gas in your oil and how much gas is in your oil? If you have a bore scope by chance you can look in the spark plug holes to see if gas is pooling on the pistons at all after setting.

Turtle_XJ

Oil was a bit high and it faintly smells of gas. I don't have and borescope but I can try to get one.

nujeepguy

you could pull the plug and push some clean rope in and see if it comes out gassy!!

Turtle_XJ

Good idea. I might give that a shot.

tedparis

Did you crank it for a while and let it sit? Anything unusual? Perhaps change the oil and then see if it happens again. Have you noticed any difference in performance?

Turtle_XJ

Ive changed it twice and it still happens

tedparis

Okay just checking. Perhaps check in the intake and see if the gas is somehow getting in through the PCV system? I really don't know what it could be if the injectors are functioning correctly. The only though would be if the injector is leaking and the valves aren't sealing all around then gas could be getting in by pooling on top of the valves and dripping down to the piston and so on, but your compression looks good. Cylinder 3 is the main suspect.

Turtle_XJ

So do you think if it was going to leak down through any cylinder it would most likely be #3?

Turtle_XJ

I haven't been driving it to much lately and I changed the oil a few days ago. After 50 miles and a couple starts and stops the oil has no viscosity left and drips like water off the dipstick. It wreaks of gas.

I need some more ideas guys.

BlueRidgeMark

A leak in your exhaust will cause the O2 sensor code and make it run really rich. The computer thinks you are running way too lean, so it dumps fuel into the engine.

Also, the 02 sensor may be a simple fuse issue. If the 02 heater doesn't get voltage, you'll throw the code and run stupid rich.

Turtle_XJ

I thought that to but all my fuses are good and if it was causing it to run rich wouldn't it increase my idle or something? Or would it not because it doesn't have enough air?

BlueRidgeMark

It will tend to idle a bit rough, but an exhaust leak isn't going to increase your idle.

Check your tailpipe if you haven't already. See if it's very sooty.

Turtle_XJ

I didn't figure it would but if it makes it run rich would it increase the idle a bit?

BlueRidgeMark

Not necessarily. It will have a rough or unstable idle, though.