So....my xj is making a strange noise. It is something like a knocking noise. It only does it when under load and driving and only when I first start the jeep and start to drive. The speed of the knocking sound increases as the jeep excellerates. After driving for a minute or two it completely stops and won't do it again unless I shut the jeep off let it sit a little and then start it and start to drive again. Then again, it only does it at first and under load. After a minute or two it completely stops. I've never had a vehicle do this before. Any ideas?

 

Is it a KNOCK or a Tick/Tap?
If it's a tick/tap it's totally normal. Normal meaning all AMC 242's (4.0 I6) do it.

 

Its kind of a knock....kind of a tap. What ever this is...it isn't normal. Its not lifter chatter or any noise like that. My Jk and Wj both had a little lifter noise when first started. It doesn't sound like a rod knock at all. Sounds like it is coming from the tranny area. What ever it is....it is LOUD.

 

The tyranny isn't slipping. Everything is shifting like normal. I described it to someone else and they said possibly the catalytic converter going bad. Anyone ever heard of a noise like this from that?

 

Kind of sounds like this.


Except it doesn't do it when parked. Only when first started and then when you take off and then it gets faster and louder with excelleration. Once the tranny shifts it quits and won't do it again until the jeep is shut off, started again, and I take off. I'm totally stumped!

 

Oh, i thought you mean it only did it the first few moments the engine was running. If that was it, it could've been the lifters.

I'm guessing the flexplate is cracked, that seems to be another reoccurring issue.

 

Bump for help.......

 

Are you hearing the vapor recovery valve on the firewall pulsing? (if 2000's still use that sort of arrangement). From inside, it sounds like a rod knock.

 

No. That for sure isn't it either. I'll have to get a video the next time I drive and post it. It sounds as though it's coming from the tranny/bell housing area. Or possibly the oil pan area. I've had the inspection plate off the bell housing. Flex plate bolts are tight and there are no cracks in the flexplate I can see. It has me stumped because once the jeep has been running for about 45 seconds it won't do it anymore.

 

thinking

exhaust leaking maybe

 

Lifter knock is not normal. It is dirty lifter.
The only normal knock is injector knock.

 

It is on this engine. Every vehicle with this engine (AMC 242ci) That i have ever listened to has a slight tick in it.
Not saying it's suppose to do it.


Anyways, That flexplate video, that's the exact noise my Jeep is making (just not as loud), but i know it isn't the flexplate because i don't have one (5-Speed Manual).

 

A good way to test EXACLY where it's coming from, take a long screwdriver and touch it's head to a spot you want to check, then put you're ear to the screwdriver's handle. this is how i located my knock.

 

Sorry is this coming from the engine, right? Not the drive train?

What oil filter do you have on there? Is it orange with bedliner?

 

Oh **** that reminds me, i need to buy a new oil filter. I keep forgetting.