New noise, rough riding

On the drive home today I noticed that when accelerating in 4th and 5th gear the whole Jeep was shuddered from a new and sudden vibration. Not the normal Jeep vibration, but something much more noticeable. When I got home I did some basic maintenance stuff (fuel filter and Sea Foam) and then went to a car show. On the way out there the vibration became increasingly worse and I noticed it was not only when I was accelerating, but when I would use engine breaking.

On the way back the ride was much much worse. Before the vibration was most noticeable at around 55mph, but now it's gone down to 45 mph. You can even feel it when in the lower gears, mainly 2nd and 3rd. It's not as fast paced as it is in 4th and 5th, but you can still hear and feel it. I know it's not tied in with the RPM's as it doesn't change in intensity with changing RPM's. It doesn't mater if I'm accelerating soft or hard, the vibration is there and it's very annoying. I'm not positive, but I think it may have something to do with the firing order, which could be an electrical problem.

Specs: '87, 3.5" lift, 31's, engine basically stock, no SYE, AX15, np231. I did a basic tune up about a year ago. Think it may be time to do it again?

You might check for a fouled plug or a dead injector.

Bad u-joint? If its not changing with the engine rpm, its not the engine.

Could be. I know the drivers side front axle u-joint is shot. I have the replacement, but haven't swapped it out yet as I couldn't get that dang axle nut off.

Would something like that really cause the whole Jeep to vibrate?


Wait, are you talking about a driveshaft u-join or....?

I was thinking driveshaft as it sounded like this was load dependent. A front axle u-joint can cause a lot of vibration, but that's usually noticeable in the steering wheel as a shimmy as well.

Well I took it apart up front and got the shaft with the very worn out u-joint out. I also noticed my lower control arms are not as tight as they should be and when the brakes are applied the whole front axles rotates backward.

Once I finish that I'm going to check the plugs. I'll let you know how it turns out.