My XJ is 5 speed, I6 with about 160K miles on it. While driving in any gear if I hit a small incline, the jeep slows. If I give it more gas, it makes a rattling noise under the hood. It has gotten progresively worse over the past few weeks. The rattling started when I was at low rpms trying to accelerate. Now it rattles even at higher rpms.

To make matters worse my waterpump took a crap this morning as I was about to go to work. Fluid went everywhere.

Anyway, since I'll be replacing the pump, do you think it might be the timing chain cause that noise and the loss of power?

Is the rattling you mention detonation? That is what it sound slike to me since you get it under acceleration.

Forgive my ignorance, but what is detonation and if that's what it is, how do I fix it?

Don't ever worry about getting flamed by me. The only dumb question is the one you don't ask, K? Detonation is like a knocking sound you get under acceleration. Sounds pretty much like the valves are all loose and are fixing to rattle apart...pretty much. There are several things that can cause it. The two most often causes are timing being off and having very crappy gas. The newer XJs I believe have a knock sensor in them and yours might be bad. Since the timing is controlled by the computer, I really don't think that the timing being off is your problem.

Could be spark plugs too. When is the last time you checked them and if you have changed then did you check all the gaps even though they say they come gaped don't trust them.

Plugs are new, gas is Shell 93, but it does sound like things are about to rattle apart. I'll see I can locate the knock sensor. Thanks.

Thanks shipmate. Is there a way to check if it's bad? I know it's a process of elimination, but don't want to spend $50-70 on a part that works.

-Nevermind, found the answer in a Haynes manual. It says to connect a timing light and have a buddy strike the engine near the sensor, if ignition retards, then the sensor if funtioning.

You will need a voltmeter.

Ok. If it's not the knock sensor, the gas, or the plugs, then what is it?.

There is only one reason the engine "pings"... high cylinder temperature.

High cylinder temperature can be caused by:

overheating
restricted exhaust
lean fuel/air ratio
advanced timing
cheap fuel
malfunctioning EGR

among other things, I'm sure

It would be nearly impossible to diagnose a detonation problem over the internet without a lot of help on your end.

Thanks. This gives me some more things to look at. Someone else had mentioned the cat might be cloged. I guess I'll start there. I bought the new fuel filter too, so I'll give that a shot.

My frustration wasn't with you all of course, it was with my Jeep. If I came off wrong, I apologize.

I replaced the trasnfer case seal about 2 months ago and the damn thing started to leak again.

I will say this: this relationship between my XJ and I, is LOVE and HATE at times.

Lack of power can be caused as mentioned by lean air/fuel mixture. When was the last time the o2 sensor was changed? Nobody ever changes them when they should. They just run them for a couple of hundred thousand miles.

I bought this rig used, so my guess never. I'll check it out. Thanks.