Renix 4.0 Running Rough

[ComancheFan]

So last night I noticed my Jeep was shaking more than normal while driving. What I noticed the noticeable more shaking is only happening while the truck is under load. I checked all my ujoints and there’s no play there. I have a 5speed ax15 tranny and it appears that I can slightly move my transfer case with my hand is this normal or should there be no play? Also I tried to let the clutch out on a hill not moving but under load and the truck started shaking then aswell. It almost feels like a engine issue and can be felt in the steering wheel. What I’m wondering is should I fix the transmission mount and go from there or should a slightly loose transmission not be able to cause this?  

[Minuit]

It's worth checking for sure.

You might be able to make the trans move a little bit if you really rock it around (that's just the compliance in the mount) but it shouldn't move very much and it certainly shouldn't be easy to shake it around.

 

Check the motor mounts too. The three mounts all work together to support the drivetrain.

[ComancheFan]

There definitely is some play in the motor mount right by the distributor. Also I noticed that the truck only shakes 3000rpm or less if I’m above that there doesn’t appear to be a issue. 

[ComancheFan]

Ok update. I had a retired Jeep mechanic look at it. The issue is something with the engine. I changed the plugs and checked the fuel pressure. The idle pressure is at 30psi and without the regulator plugged in it’s 40psi. Also when under load at idle it’s at 30psi. I’m thinking I may have a bad sensor. 

[87MJTIM]

What year and engine do you have?

 

How can you have the truck "under load at idle"?

 

Those PSIs sound about normal for a Renix.  

[ComancheFan]

It’s a 1988 4.0 Renix. I tried to load test the truck by putting the parking break on and letting out the clutch while giving it gas. However when I put the truck in 4wd low it doesn’t seem to have any vibration issues. Also if i baby the gas and barely take off it doesn’t shake. It’s 800-3000 rpm if I give it decent throttle in any gear it will shake. 

[olddude]

Check the universal joints.

[ComancheFan]

First think I checked. They took a little grease but there no play in them. I also just got done with changing the motor mounts. It’s odd I drove the truck about 50 miles today and for about a 2 mile stretch it completely stopped shaking. I’m starting to think it might be a engine issue. I’m going to try a set of wires and see what happens. 

[ComancheFan]

Ok so I have replaced both motor mounts and transmission mounts and the problem persists. I drove the Jeep about 200 miles since doing all the repairs and for about a 20 mile period it stopped. I can definitely say it’s a engine related issues not only because there’s nothing left in the drive train that could be causing this but it’s gotten worse and I can feel the truck misfiring. I’m going to try a new cap and rotor with wires and go from there. However I noticed my right directional is blinking fast and there are no bulbs out, dose my ignition system share a ground with one of my lights? 

[cruiser54]

Last time it had plugs, wires, cap and rotor?

 

do Tips 1 through 5 on my website also.

[ComancheFan]

just tried wires and no change. I changed the distributor a couple weeks ago and that came with a new cap and rotor, it ran fine for about 350 miles since I changed the distributor then it started acting up. Tomorrow I’m going to check all the grounds and install a chassis ground. One thing that’s was odd is I put my Jeep TDC when I installed the distributor and didn’t want to run when I indexed it. While I was at work I had my dad take a look at my Jeep and see if he could get it going and he pulled the distributor and slightly turned the oil pump screw about 6 different times and got it started. Like I said it’s ran good for 350 miles but maybe it’s possible it’s something with the distributor?