99' 4.0 Dieseling sounds at warm up.
 

I saw another recent post here where a member has a renix that sounds like a diesel. My 99' has the same issue up on start-up. I checked my flex plate about six months ago, every bolt. They are fine.

I saw another post about the oil filters going bad. I have a mobil one oil filter. Maybe a year old.

Is it probable to have loose valves at 160K?

What else can make that sound upon start up (I haven't really noticed it idling at a light, or anytime other than start up)?

How's your oil pressure?

Thing is, more of these 4.0's sound like diesels than do not, especially when they accumulate some miles and the motor is cold. Most commonly it's piston slap or lifter noise, or a combination of both. Neither is harmful, IMHO.

How long does it take for the noise to go away? What weight oil do you have in there?

Not likely to be a valve problem but a vacuum gauge will identify that.

Some good points Radi.

The sound is only when cold (engine) and seems to go away after about 60 seconds. I forgot the weight of the oil, 10W40? IDK.

What brand oil filter do you have? and what weight of oil are you running?

NM on the oil weight. Guess I should learn to f'ing read :pinch:

Oil filter is important though, if you have a fram.... Get that sucker off.

Post #1
"I have a mobil one oil filter. Maybe a year old."

LOL JK.

Sob... O - 2

you oil filter is a year old? :icon_eek:

Can't believe it hasn't been said. I should piston slap you guys..
No really this sounds like its piston slap. Very common on lots of cars/trucks

I meant to say that mine also has the diesel sound. Sometimes it goes away, sometimes it doesn't.

All these drivetrain problems I am having is making that v8 sitting in the carport look awful nice

Erm... post #2. :D

Why do you have a year-old filter on a 4.0? M1-204 or M1-301?

Yeah, learn to read. LOL!!

Why not just change the Mobil 1 filter for giggles. Maybe you got a bad one.

Ever shine a light into the oil filler hole and assess the sludge accumulation in there?

Sorry for the late response. I just started college.... Mindf*cked.....

I guess I can change the filter in the next weekend or two. It is a year old because the oil looks pretty darn good still. I don't buy that 3K miles bs. Secondly, my wife's Ford Ranger (96'-engine by Mazda mind you) has 300K miles on it, It has had maybe TWO oil changes in the 9 years we've been married. She just never did um (chick thing I guess). That truck is a vampire and runs AMAZING! It is crazy really. An abnormality really-but it thinks it's a Mazda.

I'd never do that to the XJ, but I moved states and started school in these past few months so it really hasn't been a priority right now. If the oil looked dark, I would feel completely different. I do plan on doing the O/C within two weeks. I'll let you know if it went away if you are still following this.