Hey all I know this is way WAY off topic, but hey, this is FTE, off topic is our specialty.

Dad just bought a "project". It's a 2002 Jeep Liberty that he picked up cheap with a "rough running" issue. Knowing full well that it was possible that it was a valve issue.

Drove it home and pulled the coil on plug connectors one at a time until We narrowed it down to the #2 hole. Pulled the #2 spark plug and it was wet (with oil I think). Well we tested several things and ran a compression test on all 6 cylinders. I got good readings on all but number 2 which shows NO compression. So, when I applied air pressure to the #2 cylinder, I got air out the intake (with both PCV Valve tubes removed, so I know it's going through the intake runner and not leaking back into the intake through the PCV Valves). So I am guessing that I have a stuck intake valve.

So long story to ask this question. Is there anything that can be done without removing the head? Is there a chance that the valve lap adjuster (hydraulic with overhead cam) is stuck up too far and not allowing the valve to close? Is there anything you guys can suggest without me ahving to pull the head? I know there have been issues with these 3.7's and the 4.7 V8's losing the valve seats, but I guess I don't understand how a slipped valve seat will hold the valve open. I would think that would keep the valve from opening, not from closing. Let me know your thoughts and some suggestions. I have posted this on a Jeep forum also, but I trust you guys here at FTE a lot more than these Pentastar guys.

This 3.7 V-6 is not the 4.0 Inline, that's for sure. Those things were bulletproof. Dad is still driving one of those with over 250k on it....

 

Can you remove the follower on that valve & tap on it . May be carbon build up .

Or remove the keepers & the spring & spin it with a drill

 

I had a very similar issue with my 4.0L. Turned out to be a smoked lobe on the cam and a smoked lifter. I'll see if I can get ahold of my buddy that's a jeep tech. How many miles?

 

AIR ESCAPES THROUGH THROTTLE BODY-> INTAKE VALVE BENT OR NOT SEATED---> INSPECT VALVE AND SEAT, REFACE OR REPLACE AS NEEDED INSPECT VALVE SPRINGS/HOLDERS AND REPLACE IF NEEDED

AIR ESCAPES THROUGH TAILPIPE-->EXHAUST CALCE BENT, BURNT NOT SEATING-->INSPECT VALVE AND SEAT, REFACE OR REPLACE AS NEEDED INSPECT VALVE SPRINGS/HOLDERS AND REPLACE IF NEEDED

AIR ESCAPES THROUGH RADIATOR---> HEAD GASKET LEAK OR CRACKED CYL HEAD OR BLOCK BETWEEN--->REMOVE CYL HEAD AND INSPECT REPLACE GASKET, HEAD, OR BLOCK

AIR ESCAPES FROM ONE CYL TO THE ADJADENT CYL--> HEAD GASKET LEAK--> iNSPECT HEAD GASKET AND CYL / BLOCK FOR CRACKS--> REPLACE AS NEEDED

CYL LEAK AND AIR ESCAPES TO OIL FILER CAP OR BREAHTER ONLY-->STUCK OR BROKEN PISTON RINGS- CRACKED PISTON, WORN RINGS OR CYL WALL OR BOTH-->iNSPECT RINGS AND PISTION mEASURE RING GAPS AND CYL DIAMETER, TAPER AND OUT-OF-ROUND. rEPLACE DEFECTIVE PARTS AS NEEDED.

So sounds like you need to check for leaks between cyl and make sure its not coming out of the oil cap/breather. Then is pull the VC and take a look as what you have.

Cyl should hold around 60 psi

Morning Rick and TS

 

Yeah , we already pulled the VC. The valve is definite;y moving up and down with the cam (OHC sits right on top of the roller rocker on these things). I will see what we can come up with. A mechanic friend suggested hosing that valve stem down with WD40 (his idea, I swear) and tapping on the valve spring and keeper gently with a hammer. I may give it a shot with a brass pin and see what gives. Worse come to worse, the head will have to come off, which is what we're looking at now anyway...

Oh and Tim, that would be great! 15Xk miles. No valve ticking or valvetrain noise, at all, it just misses and runs rough. (and now I see why...)

 

Ahhh forgot those new jeeps are OHC. For what it's worth, my friend told me valve issues are not common with these motors, but we all know a neglected engine can do some funny things

 

I'm not sure how common this issue is, but there sure is a lot of info on the interweb about it. It may just be that this is the weakest point in their design and that of the relatively major things that can happen this is the most common. I don't know, but there are a lot of posts about broken valve springs, dropped valve seats, even a fairly distrubring issue with the rockers popping off the valve and rattling around inside the VC. Not sure how much to believe, but I will give it a shot tonight and let you know what I find.

 

Well, nothing good to report.

Here's what we did tonight: Pulled the camshaft, rocker, valve keepers and spring. The spring is fine, no broken spring for sure. Even with everything out of the way and the spring pulled I still get air out the intake when I put air pressure to the #2 cylinder. I am thinking at this point that is has to be a burned or bent valve. I can spin it with my fingers and hold it against the seat and I don't really feel anything that catches or feels like it drags. Since I am still losing pressure though I am thinking that the valve must be burned or bent. I guess I will be pulling the head unless someone has a better idea.

 

I'd bet burned ....

 

Yeah in talking with my buddy a bit more, burned valves are somewhat of a common occurrence on that motor

 

That's what I have heard too. Dad is weighing his options as to whether to buy a used head or just to have this one gone over when we pull it, but I guess if it's just a burned valve, we wouldn't need either one... I think we are going to pull that head this evening and see what lies below...

 

Good luck. Done plenty of work on 4.0 but never those 3.7's

 

Yeah same here. We completely tore down and rebuilt the 4.0 in my dad's grand, but this 3.7 is a different animal all together. All aluminum, no more cast iron for Jeep I guess. Too bad that 4.0 is as close to bulletproof as anything that Chrysler has made.

 

Yes sir. I love working on them, so simple. We have one now completely tore down. Just got the block and pistons back from the machine shop. Got the block for free, lady never changed the oil for 55k miles, still had factory mopar oil filter on it. Block had to be bored .30 over, but it will be nice when we are done

 

Yeah the only beef I have about them, And it is more Chrysler than it is the engines themselves is that they use a different block in the GC than they do in the Chreokee, Wrangler and even the Commanche Pickup. I cannot explain why, but the Grand Cherokees have different holes in the block for the style of motor mounts required for that vehicle. Really kinda stupid in my opinion, but it is a great motor for sure. Almost as bulletproof a motor as the old Ford 300cid straight six.