I wonder if this is a normal attitude on 4.0 engine. I saw engine mounts are old and micro cracks on rubber fyi.

when running on LPG it is little rough(not so critical but it is there and bugging me) , on gasoline it is better during idling, but it feels like there are misfires all time, engine cold or warm. But under load, during kick down, during braking, engine is running very well and fuel economy is ok. I experienced ignition problems on several cars, it feels something different.

What can be the reason for this? Spark plugs, cables, distributor roto is now, distributor cap is old, but there is no a major problem on contacts. little wear on all contacts. There is 3/4 inches crack crack on exhaust manifold on joining point of two sets of fron three and back three cylinders. It makes little noise but again i heard this on my previous car and it was idling perfect.

A burnt or sticky valve? Any ideas? PCV? EGR? Crack on intake manifold? Help me to find out the reason please. I met with my friend which i sold my previous car,pathfinder, i started his car, it has 160k miles on its odometer but it is running smooth. ZJ is on only 86400 miles.

 

Mine does the same thing. There is a thread on here about a "jumpy idle" that has some info in it. It almost sounds as if this is normal. Some have gotten good results using Seafoam in the gas tank and intake. I think I'll try at some point. Keep us posted on what you find out...

 

i did not try seafoam thing, because i am unable to reach that product, becase it seems it is not sold out of states. but, surprisingly i was able to find GM combustion chamber cleaner spray form chrysler here. Surprising thing is they do not even know what that is. And they have lots of in their inventory! i paid almost USD 10 and applied it from intake manifold. Slowly spraying without allowing it to stall.. It tok few minutes to empty the can, then i let it stay for 1 hour or so. Then restarted, it started well and idled better but that feeling... it is still there. It is less on gasoline but i have dual fuel setup for LPG, so it is much more evident on LPG. This reminds me ignition problems... my distributor cap is not so worn but still old, i may need a GM made distributor cap.

Oh, i tried that dollar trick at exhaust to see if there is a valve problem but it is not sucked to exhaust pipe.

I think i need a vacuum gauge and its adapter to check compression of each cylinder.

 

no ideas?