Knocking when decelerating.

[GregSawyers]

Hi, I'm new to this so I'm not sure I'm doing it right. I drive a 1977 CJ7 with the AMC 258 i6 / 4.2l i6. It has its problems with minor oil leaks but that's manageable. However in the last couple of days I have been getting a knocking when decelerating at around 5 to 10 mph to stop. It is the worst in neutral and doesn't happen every time. However it is much louder and happens more frequently in stop and start traffic and parking garages. Any input would be great.

 

[Lumpy Grits]

:ww:

Did you check the engine oil level when this started?
Get under the Jeep and put a wrench to EVERY nut and bolt you can.
Are the manifold bolts tight?
Did you play with the timing or carb settings before this started?
Check the ign timing to be sure it's 'rite'.
What weight engine oil are you run'n?
LG

 

[GregSawyers]

My oil level is right at the full line, the valve cover bolts are screwed in pretty well, same for the intake/exhaust manifold. I just tuned the carb a couple of weeks ago so that should be fine, and I'm using 15w 40 rotella. I believe the noise is more of a grinding knock, and more from transition or rear axle, something around there. The engine seems to be in pretty solid shape.

 

[JeeperChris]

Are you sure it's not a bad exhaust system? My header has some leaks at the head and the muffler is a solid piece of rust. When I decelerate I get all kinds of little popping sounds and more.

Just a thought.

 

[GregSawyers]

I hadn't thought of that, I know the exhaust pipe and muffler is only a few years old but I believe the headers are original to the car. I'm taking it to my mechanic next week, I'll have them look at.

 

[Lumpy Grits]

CK your U-joints and slip spines for slop.
When was the last time you greased the slip spines and U-joints?
Also-Make sure the exhaust isn't hit'n somedangthing.
Check you motor mounts and tranny mount.........
Have you confirmed the ign timing with a timing light? You really need to!
LG

 

[Bartman1959]

CK your U-joints and slip spines for slop.
When was the last time you greased the slip spines and U-joints?
Also-Make sure the exhaust isn't hit'n somedangthing.
Check you motor mounts and tranny mount.........
Have you confirmed the ign timing with a timing light? You really need to!
LG

I'm glad I read ALL comments before I post any of my own. Your comment was the exact as I was going to advise.

Bartman
Retired USAF