So, I have a tap / knock that started recently in my jeep. It seems to be coming from the passenger side of my engine. I can hear it through the firewall when the doors are closed and I am inside. It is variable with engine speed, and is not the purge valve. I can feel it by touching the distributor cap, but I am ignorant about internal placement of things in this engine. Others have told me that it sounded like a lifter, but that they weren't sure. Those folks told me to get cd2 lifter doctor or use Marvel Mystery or something like that. Would a lifter being stuck cause enough of an impact on the camshaft to be felt on the distributor? I can't feel the tap on the engine near the distributor, only by touching the distributor, itself. Or is this something that is more likely a distributor specific issue? The engine runs fine, no other issues ... plenty of power, etc. I have tried to make a few videos to hear the sound, but it is not audible enough (yet?) to hear over standard engine noise / exhaust.

Any thoughts are welcome. I will not have a chance to do much more to it for a few days, as we will be tied up through the weekend.

Thanks

 

Remove the distributor cap and check to see if the distributor shaft has too much play in it.

Grab the rotor and see if you can rock it back and forth (side to side). If so, the shaft bushing in the distributor is worn out. A little rotational play is normal.

 

I just now got a chance to even get in my jeep for the first time in a while.

I popped the cap off the distributor and there is more side to side play in the rotor shaft than there is rotational play. Could this be what is causing this tap or knock? I wonder more because the noise kind of came out of nowhere.

Is this bushing something that is user replaceable or am I going to have to go replacement distributor?

 

Last night, I didn't get a chance to make a video, but thought of it tonight when I got home and wanted to link it and see if it made it easier for someone to help me narrow down this noise.

The noise does not seem to get better after even 10-15 minutes of driving. It also does not get worse. Pretty much a constant.

Again, you can feel the noise in the distributor cap and nowhere else. I can also hear it with a stethoscope when near the dist. cap the loudest and it gets less as I move away from there. I tried to rev the engine a bit during the video, but I think that wind noise from the fan muffled the sound in the video. The noise does speed up relative to engine noise. I think that the sound stays about the same loudness, but seems to drop in volume just due to the overall loudness of the rest of the engine increasing.


The tap-tap-tap is the noise I am more worried about. Please excuse the squealing ... that is my idler pulley and I haven't gotten it replaced, yet.

 

Without standing there with you, it sounds like a lifter, but with you saying that there is side to side play in the distributor shaft, you need to address that before it leaves you on the side of the road.

If your distributor rotor is tapping against your camshaft position sensor, it will eventually break it - then everything stops.

If it is a lifter, you can try Kreen, Seafoam or MMO to try and clean things up in there and quiet it and the other lifters down. Mine sounded like a diesel until I hit it with Kreen and an oil change 500 miles later. That quieted the lifters down significantly.

 

So, I ordered some Kreen and it came in on Saturday. I added it to my engine oil, which had about 300 miles on it and started driving. I had an errand I could run about 20 miles away, so I went there. By the time I got home, the tapping was gone. The next day (after engine was fully cooled) the tapping was back. I drove in to work this morning and went a little out of my way to let the enging run while fully warmed for a little longer than my typical commute and the tapping was again gone. I think that I have traveled a little over 90 miles since adding in the Kreen and it will go away after running for about 25+ minutes. This was not the case prior to adding it. It would tap after a 75 mile trip.

I have a distributor on order and also an idler pulley, so I hope to quieten this thing down some.

This lifter tapping (assuming that is what it is) ... is that something that spells the end of my engine in relative short order or is that something that can allow me to drive while I save funds for a future repair of greater magnitude?

 

I'm no expert on the interiors of these engines, but I can say that with both cherokee's I've had, they both had lifter tick every once in awhile, particularly after being driven for awhile and then sitting idle for 5+ minutes on a warm day. It will sound like it's right up top near the oil fill hole. If it doesn't happen all that often it's probably fine, as these 4.0's all get 2 distinct noises - this random lifter tick/tap sound from up top, and (particularly the older ones) get that bottom end *fwap fwap fwap fwap* noise from time to time as well.

I ran MMO through my renix and it did get rid of a bit of the smoking I had going on with my blowby, so that was nice. I also ran a can of Restore when I did my last oil change. A few days later I started up and heard a lot of clunking going on - a lifter must have gotten stuck, possibly due to a lot of gunk getting broken up and thrown around because of the restore. Ever since then (a few thousand miles later) and it's been totally fine. I guess I could safely recommend either product.

 

Lifter noise is a fact of life with the 4.0. Mine has made lifter noise to varying degrees since I bought it in '94. Kreen did the best job (IMO) in cleaning the engine up and reducing some of the noise, but it is something that has always been there. I would not worry a bit about it - I haven't for 246k miles.

 

Judging only by the sounds... it's not a lifter. Even though it speeds up with throttle action, it just doesn't sound fast enough to be a lifter.

I'd say distributor as well. Sounds like your belts are loose, so that tensioner should help.

Let us know, we're here for the beer... er.. help. LOL!