[justinking06031]

Picked up a 91 XJ for kicks - It was $200 bucks -- 148kmiles, 4.0, AW4 Auto, 4x4...

The motor is blowing a little white smoke out of the CCV/PCV lines(and the oil cap if it is off). I took the air box apart and there is about a 1/4" of oil in the bottom and the paper filter was soaked with oil. Engine starts and runs fine(up to 40mph; then it misses like crazy). It idles fine -- the oil is dirty, but is made up of only oil, and the coolant appears to be dirty but no oil in it. There are absolutely no leaks in the engine area(the tranny pan is leaking, but that's neither here nor there). I started today by doing a compression test(thinking maybe I was having blow by on the some of the piston rings) and these are the results -- will you guys give me your 2 cents on what you think may be going on?

Cyl 1-90
Cyl 2-100
Cyl 3-135
cyl 4-120
cyl 5-135
cyl 6- 102


Dont get me wrong, I know I bought a POS, just looking to have some fun with it(that involves cresting above 40 mph now and then)

Thanks in advance,
Justin
Semper Fi

[Felonious_monk]

I have always been told....

Anything below 125 Psi is on its way out.

Also, you shouldnt have more than a 10% difference between cylinders.

If you have two cylinders next to each other with similar low readings.....further testing shoudl be done to check for either bad head gasket, or valve trouble.

I just check my compression the other day.

1988 4.2L 143,000 miles all cylinders were between 145-155 Psi

[Pillswoj]

^ X2 It looks like 1, 2, and 6 are shot and 4 is on its way out. Question is if it is rings or valves. If you redo the compression test squirting oil into the cylinder before the test you will get an idea, if the compression comes up it is rings if it stays low it is valves.

As you don't want to drop alot of money into it there are a couple of things you could try.

1. If it is valves try seafoam in the crankcase oil (I would not normally recommend but what have you got to lose). It should clean the valves if the problem is a build up and could help. The danger would be that it would loosen crap that could block an oil passage and make things worse.

2. I would try Auto RX (google it) the problem being it works over the course of 5 or 6000 miles and it does not sound like you will be putting that sort of mileage on it.

3. Rebuild the engine.

# 3 is the correct answer but it will depend on your budget

[justinking06031]

**UPDATE**
I learned I am an idiot, and didn't truly have the spark plugs out (open mouth, insert foot) -- So I redid my test today.

Just to confirm, cold engine - all plug wires labeled and pulled off and out of the way, coil disconnected, plugs removed...

first test was with dry cylinders
cyl 1 - 127
cyl 2 - 140
cyl 3 - 160
cyl 4 - 155
cyl 5 - 160
cyl 6 - 115

with 8ml of motor oil injected and then the same test performed:
cyl 1 - 115
cyl 2 - 160
cyl 3 - 180
cyl 4 - 190
cyl 5 - 200
cyl 6 - 140

I also hooked up the leak down gauge and pushed 100 psi in and all cylinders held air for 10 minutes each -- no loss whatsoever.

I put in the new champion stock plugs I was going to put in our YJ in(since they were there) and took her for a test drive, still nothing -- of course I was burning off all the oil in the cylinders so I have lots of white smoke. Still won't go over 40 -- I am wondering if my problem is elsewhere(ie fuel pump) -- It still starts and idles fine, but when you give it more than 1/4 throttle it misses terribly...

Sorry for the initial screwup - I have seen the errors in my ways and I appreciate the help....

I can post pics if someone really wants to see what a POS jeep looks like

Justin

[Felonious_monk]

I would still think that there is something wrong with cyl #1..............it doesnt make sense that the compression would go down after adding motor oil. Going up or staying the same yes. But to lose compression after adding the oil means you missed something. Plus you are still outside of a 10% difference in compression between cylinders.

Adding oil should not produce white smoke. Blue, yes. Even black. But white almost always means coolant in your engine.......does the white smoke smell like antifreeze?

I always have checked compression on a hot/warm engine. Also, make sure that you hold the throttle wide open while you are cranking the engine over.

[jgorm]

Looks like the motor needs some work. You could get one of those things that look for oil in the coolant. Hopefully its just a warped head gasket because 1 and 6 are much lower than the rest. The rings look like they don't have the best seal either. Did you do the leak down at TDC for all cylinders? I would also do the test with a warm motor as mentioned above.

[justinking06031]

I replaced the spark plugs, tested the plug wires(all are reading between 5-8 ohms), replaced distributor cap, rotor, and fuel filter. I also replaced all the vacuum lines on the top of the motor with new ones...

I did not put a new air filter element in it yet, however I cleaned out the airbox and it is hooked up... Not sure where to go now.

When I replaced all of the above components, I can now rev the motor all the way up to 5500ish but I still cannot drive without it falling apart at about 30-35mph... Tranny fluid is a quart low, so I am going to add that in, but I wouldn't think that would be enough to cause the driveability problems...

Yes I was at TDC for the pistons on the leak down test - and I have not had a chance to do it on a warm motor yet -- Uncle Same has me working hard lately

Semper Fi

[superadd]

Sounds like your losing power under a load. Not sure which that 4.0 has electric or vacuum advance try unhooking which ever it is and see how it reacts when you drive it.

Yes that number 1 cyl is a bit low and wierd maybe you didnt get the gauge good and tight the second time but there is not enough loss of comp to make the motor loose that much power under the load.

Your leak down test is good shows no warped head or head gasket for the most part.
I would check the fuel filter and fuel pump and get rid of the oil soaked filter