Jeep Strokers

UPDATE:

My mechanic installed my 4.6 "Rockcrawler" motor and it seems to have a vibration around 3200 rpms. He said it wasn't a fuel issue and is looking further into it. Does anyone know what could cause the vibration?

How heavy of a virbation?

Poorly balanced rotating assembly, stiffer motor mounts (not really cause, just transmits it more) bad balancer, out of balance flex plate/fly wheel.

Thanks for the info. Also, I want to add that I still have the factory airbox and exhaust system. My mechanic said the fuel trim looks good, even at 3000-3200 rpms where the vibration starts.

Well, my mechanic gave me back the jeep for the weekend. He was wrong when he told me the motor only vibrates from 3000 rpms and up. It vibrates at any rpm. There's a local machine shop guy that's going to take a look at it on Tuesday. We'll see what he says...

How bad is this vibration?

SilverXJ wrote:How bad is this vibration?

It's not horrible at low rpms, but definitely very noticeable. It really starts to shake things up over 3000 rpms. I don't really know how to describe the intensity of it.

UPDATE:

My mechanic couldn't find the source of the vibrations, so with my permission, he took the motor back out of the jeep, crated it up, and sent it back to S&J Engines. They took it apart, checked the weight and balances of the components, and told me that it was perfectly balanced. They charged me $350, put it back together, and shipped it back to my mechanic.

My mechanic then re-installed the motor, did some more tests, and couldn't get the motor to stop vibrating. As a last resort, he suggested that I might have him remove the M.O.R.E. Torsional Rubber motor mounts and have him install some O.E. motor mounts. So, he did that and told me that the vibes were still present. I arranged to have another shop take a look at it and went down to pick it up. When I got there, I started up the Jeep and guess what? There were no vibrations! The O.E. motor mounts solved the problem! I'm extremely happy in one way, but I'm also pissed at the same time. Not only has my jeep been in that shop for the past 3 months, but I had to pay the builder another $350 to look at it and my shop charged me an additional $1200 to take out and re-install the motor.


I already plan on speaking with the shop's manager on Monday about not charging me the additional $1200. What would you guys do in my situation?

reducing timing via PCM tuning can also alleviate any pinging that would otherwise be there with a stock timing map. I've used the accel injectors but I tend to steer clear of them.

You had MORE mounts and left them in the whole time? Your own fault.

SilverXJ wrote:You had MORE mounts and left them in the whole time? Your own fault.

How do you figure that? The mechanic checked to make sure they were good and insisted from the beginning that the motor mounts weren't the problem.

FlyinRyan wrote:reducing timing via PCM tuning can also alleviate any pinging that would otherwise be there with a stock timing map. I've used the accel injectors but I tend to steer clear of them.

Good to know. Thanks for the info. As of right now, there's no sign of any pinging.

MORE mounts are known to transmit more vibrations than stock.