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[supersparks]

hi all i have a 2002 wj with 70000 miles done last 20000 on lpg with full service history. there is a slight tapping from the top end and what sounds like an exhaust manifold blowing but after changing the gasket and fitting a different manifold the noise is still there . my real question is is there any real known common problems to give these symptoms like hydraulic lifters , soft cam lobes, compression problems etc.

[daggie]

lazy lifters ? that all I can think of, on of ours does it

[JamesH]

Mine's always had a slight top end tapping sound, from 67K miles when I got it to 140k miles now, not got any worse, last 65k miles on LPG.

[Dave69]

have you done an engine flush and new oil ? can solve the problem

[allante666]

Metallic tapping, sounds like one stuck lifter, worse when cold but gradually gets quieter as it warms up to normal temp. Still audible when hot and louder on acceleration?   Piston slap! Have it on mine, tried everything to diagnose it until I finally had the head off and  had a look.
It will eventually wear the cylinder elliptical. The other, but just as bad, cause can be the piston skirt breaking up. (metal chunks in the oil pan is a sign)
Ive done loads of investigating into this to try and convince myself it was just a lifter but sadly not.
Mine still runs ok but I have got another engine on its way!
If this fits your symptoms give me a shout if theres anything you want to know about it. It fairly common, just go on youtube and search for jeep piston slap, theres loads of videos of it.

[supersparks]

well what can i say thanks for the diagnosis of what i was hoping was a very small glitch, when you are actually telling me my engine is fubared. did you look into doing a rebuild with a bore and new pistons, if this is a common problem how do you know you are getting a decent replacement engine.mine has done 75000 miles with full dealer service and is running on proper expensive fully synthetic oil so my point is if this has gone what is the chance of finding a decent second hand engine

[Mike Pavelin]

Stop worrying. If you think it's tappet noise, I'd reccomend an oil change followed by Forte' hydraulic tappet treatment. It really works.

[Bishops Finger]

It will help if you remove the LPG system and advertise it for sale on a post card in your local post office.....

[JamesH]

Don't bother with expensive synthetic oil when you have an 80's tractor engine under the bonnet.

[allante666]

Supersparks yes I briefly considered a rebuild but thought better of it. I reckon once you had paid for six pistons, rods, bearings, probably had the crank ground and a rebore it wouldnt have been financially viable.
How do I know the replacement engine isnt as bad? I dont. Im taking the guy at his word. watch this space..
Of course it could be a stuck lifter, you never know but if it fits my symptoms, its probably not. If you could disconnect each spark plug in turn and see if one stopped it, it would probably mean piston slap as the tapping noise is caused by the cylinder firing and the piston, being worn tilts in the bore so the skirt taps on the cylinder wall. with no spark on that cyclinder it wouldnt tap as the piston wouldl just be being moved up and down by the crank, hence why its quieter when you take your foot off.
I couldnt do that as I have the distributorless ignition with the single long coilpack but, as ive just realised as I type this (duh!) I suppose being lpg you could just clamp off the rubber hose to each injector in turn? not quite as accurate but should help diagnosis.
I still have some video clips I took of mine rattling and also the movement in the pistons which I took to send to a mechanic buddy of mine in the states if you want them.