Cylinder dead and now alive

Yeah, not much info here. Have you tested the compression? is it a bad plug wire? How many miles are on it? Could a valve be sticking? Engines seldom heal, so hoping it goes away and driving on usually makes things worse.

F.D.S., Jeep came out with a TSB to fix this problem that occurred during the '96 to '98 model year on the 4.0L engine. It's actually a misfire condition that is caused by valve float caused by a bad batch of weak valve springs during those two model years. The fix is to replace the valve springs with the newer/stronger valve springs with a new p/n. Your dealer will have the TSB information. No amount of replacing ignition parts, fuel injectors, etc. will help. Ask me how I know about that last point? ;)

Jerry

P.S. the stalling is likely caused by a defective CPS (crankshaft position sensor) which will cause intermittent stalling totally unrelated to the '43' code.

Jerry

If that engine has a separate coil for each spark plug, it could happen easily.

Jerry, Thanx for the info. I will take it to the dealership. One question: how much did it cost you to get it fixed? TIA.

I bought the new stronger version of the valve springs (as well as new valve stem seals while we were underneath the valve cover) from the dealer for what seems like $80 or so. Then I paid a local mechanic $150 to swap the valve springs and valve stem seals. Voila, no more '43' codes. Mine was especially bad, I could get as many as three '43' codes at once... as in 12

Jerry

Naw. '96 4.0L still had a dizzy. No coil-over-plugs yet

FDS,

My '01 XJ had the engine light come on back in March. 27K on odo. Took to dealer and also told him of unacceptable coolant loss. Dealer replaced the #6 plug and sent me on my way. Found no leaks in coolant system. Told me to watch levels and keep track of usage. 2 miles down the road, light came back on and I turned around and gave it back to the dealer. Mech put computer back on and found #6 bad again. Mech grabbed stethoscope and poked around the valve cover a bit and said that he wanted to pull the cover and have a look see tommorrow. Tommorrow came and dealer called and said all was fine under valve cover and was planning on pulling head. 2 days later dealer calls and said that he ordered a new short block for me. After 10 days, got jeep back. Asked dealer what happened to block, he said that the lifters for the #6 cylinder were crushed like stepping on aluminum cans and gouged badly. Debris was throughout the lifter section. DC wasn't going to take any chances and wanted block replaced. 3 months and not quite 3000 miles and 2 gallons of coolant dealer replaced head. Then less than 1000 miles later A/C evap went south.

Brian