Collapsed Lifter = cam, lifters, roller rockers?

'90 XJ, 4.0L, AX-15

About five months ago, I started hearing a sound that very much resembled a clicking lifter. It would click or tap when cold, after engine warmed up it went away. I presumed the oil was pumping up the bad lifter after warm up, I just drove a little easier and hoped it would go away! Well now the noise is starting when the engine gets very warm, I can hear it at idle, (oil is thin & not pumping up the lifter?) can't hear it at higher speeds but am sure it is not lifting properly, I am starting to get a surging motion in the acceleration, instead of just smooth power. Could it be something other than a lifter? (Ignition system, sensors, fuel injectors all in good shape)

The jeep is still very much driveable, but is getting poor gas mileage and sometimes backfires through the intake. So, now is the prime time for new cam, solid lifters & roller rockers, have seen Hesco's, but what so you guys reccommend? Unless anyone thinks it may be something else?

Before doing anything, you need to determine if there is a problem. First -- take compression readings. If you have a blown lifter, that cylinder will not give readings close to the others. Second, remove the valve cover and visually inspect the valves as they operate. Use the washer hose tool -- take an old washing machine hose, hold one end to your ear, and point the other end at each valve in sequance to try to isolate and abnormal noises. If they all go up and down and they all tick the same, you don't have a problem. At least, not a valve lifter problem.

gixj90 said:

'90 XJ, 4.0L, AX-15
Could it be something other than a lifter? (Ignition system, sensors, fuel injectors all in good shape)

The jeep is still very much driveable, but is getting poor gas mileage and sometimes backfires through the intake. So, now is the prime time for new cam, solid lifters & roller rockers, have seen Hesco's, but what so you guys reccommend? Unless anyone thinks it may be something else?

Click to expand...

Check the EGR Valve to assure it seats properly (your 90 is non-HO).

Check the CPS to assure the leads are not fried by heat.

The noise is probably the dreaded header leak, not a lifter (take Eagle's advice and pop the valve cover for a closer look and listen).

An expensive valvetrain is a low priority in a long list of solutions to address a problem that you can better determine with a valvetrain inspection and a compression test. I would think you would hate to change all the valvetrain and still have the lean mixture bucking condition at speed?

A worn out exhaust lobe could cause a backfire from the intake, BUT....it would be continuous under acceleration.

Follow Eagle and Ed's advice ...And why on earth a solid lifter cam on the street??? You will spend eternity adjusting your valves if you drive it very much. If you don't keep it maintenanced that expensive valvetrain won't live very long. There are plenty of hydraulic lifter cams that work well.

Discussed it with other Mechanics in the area today, and your advice here. I plan on checking compression, checking the valves under operation, and if no problems, give a good tune up, then chase sensors if it dosen't quit after the tune. Thanks for the info!

Now can someone tell me how to buy the time to do the work?