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Jeep went wacky.

Get your comp test done and start looking for a good rebuilt motor in your area!
 
Results of dry comp test.
935d4694aaae68e59162e2d0ad2325b5.jpg



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Not bad but the 25 psi gap between #3 and #2 is 25 psi and the OEM spec max is 20 psi, thus it can make for a rough shake at all rpms. Other than that, compression looks good. I doubt the compression difference has anything to do with the noises. 5 psi could be measurement error, so I would worry about it yet.

You might try new valve stem seals (cheap and super easy to do) if the entire O2 sensor test passes first to solve the very rapid plug fouling.

Still need to check that FPR vacuum line for leaking fuel into the intake, stop any and ALL vacuum leaks, test the O2 sensor network, then if they are all OK assume you need new valve stem seals. Check the valve guides for any side to side slop/motion when doing the valve seals to decide of the head needs to be pulled and worked on. Also squirt some MMO on top of the lifters while you have the rods out to change the valve stem seals. That would help loosen them up and clean them faster. Also check for any bent rods at the same time!!!! Role them on flat surface.

O2 sensor jeep XJ testing bible thread:
http://www.naxja.org/forum/showthread.php?t=1012701
 
Last edited:
Compression looks ok as ecomike said , better than my 300k 4.0 .


Mike you said valve stem seals are easy do you have a write up? I've been thinking of doing this job too



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Ecomike said:
Not bad but the 25 psi gap between #3 and #2 is 25 psi and the OEM spec max is 20 psi, thus it can make for a rough shake at all rpms. Other than that, compression looks good. I doubt the compression difference has anything to do with the noises. 5 psi could be measurement error, so I would worry about it yet.

You might try new valve stem seals (cheap and super easy to do) if the entire O2 sensor test passes first to solve the very rapid plug fouling.

Still need to check that FPR vacuum line for leaking fuel into the intake, stop any and ALL vacuum leaks, test the O2 sensor network, then if they are all OK assume you need new valve stem seals. Check the valve guides for any side to side slop/motion when doing the valve seals to decide of the head needs to be pulled and worked on. Also squirt some MMO on top of the lifters while you have the rods out to change the valve stem seals. That would help loosen them up and clean them faster. Also check for any bent rods at the same time!!!! Role them on flat surface.

O2 sensor jeep XJ testing bible thread:
http://www.naxja.org/forum/showthread.php?t=1012701
Click to expand...



Going to purchase the front and rear vacuum sets and replace all vacuum lines as a fail safe. And then going to replace both O2 bad or good just for peace of mind.


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You are missing the point, I guess you did not read the O2 sensor sys testing article?

You could have good O2 sensors, but have damaged grounds, wires, connectors or a bad O2 heater power supply relay giving the ECU bad O2 sensor data. Also you can determine if the O2 sensor network is reading lean and telling the ECU to run it rich!!!!! New O2 sensors will tell you nothing about why those plugs look so rich from carbon or oil fouling.

Keep in mind the vacuum sets do not include the large tube run across the top rear fire wall to the Vacuum storage bottle under the Passenger side bumper or the Pass side AC/Heater (they go bad early) fire wall vac lines. The replacement you plan on the 2 vac line sets is a great idea, but it is not a 100% complete set. Also does not include the brake booster Vac line or BB Vac check valve.

Two of those plugs are already getting fouled, but they look way better than the other new plugs did. Not sure if the FR4s have had enough running time, but so far so good. Yes the FR5 is a stock OEM plug for a new engine, not an old worn out one with fouling issues. If you solve the fouling issues (oil or too much fuel) then go back to the NGK FR5 s.
 
Green Mesa XJ said:
Compression looks ok as ecomike said , better than my 300k 4.0 .


Mike you said valve stem seals are easy do you have a write up? I've been thinking of doing this job too



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Click to expand...


All you need is some 1/4" OD nylon rope, about 50 feet IIRC, and a valve spring compressor tool (about $18 each at Summit) and some standard tools....

Take out the spark plug and turn the crank at the harmonic balancer to bring the piston into view, then insert the rope in through the spark plug hole until no more will go in, then use the valve spring compressor tool to compress the spring, take the snap ring off the valve stem, and release and remove the spring. Then remove and replace the valve stem seal. Put the spring and snap ring back on the same valve, do both the intake and exhaust on one cylinder at a time, and then pull the rope out, and put the spark plug back in.

Fast easy and simple as hell. You do need to remove the valve cover first LOL.

https://www.summitracing.com/parts/wmr-w84001

How to compliments of Cruiser54
 
RCP Phx said:
More to the point of what I believe is going.............Remove the oil cap when it's running, see if it get louder?

Here's a good old thread on collapsed lifters!!!!
http://www.naxja.org/forum/showthread.php?t=95660
Click to expand...

As I recall (never done it myself yet) you can use a telescoping magnet to pull the H-lifters out after removing the rocker arm/rockers and rods for inspection? Is that correct?

I am thinking of installing new lifters (using the old cam) when I replace my head later this year.
 
Ecomike said:
As I recall (never done it myself yet) you can use a telescoping magnet to pull the H-lifters out after removing the rocker arm/rockers and rods for inspection? Is that correct?
Click to expand...

Sometimes that works, a dental pick or a o-ring tool can definately help! Being in the business for years I have a set of collet pullers I use.
P1080467_zpsxetnm1jr.jpg
 
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