Sputtering

[JeepFanactic]

Just picked up a 1987 MJ 4.0 with 85k miles.  It made the 200 mile trip back but once I got on the gas it started sputtering like it needed fuel. So I didnt get on the gas much.  It idled fine with no problems.  I checked for the fuel ballast resistor but I don't think the 87 MJ has one since I bought the jeep from the original owner.  Any suggestions?

[Eagle]

Clogged catalytic converter?

 

Dirty/clogged fuel filter?

[Dando]

In going to say fuel filter, with only 85k mi it could be original, I know mine was at 100k still when I bought it. And then If it is not the fuel filter at least it is a cheap part that's easy to replace and should be changed anyways for peace of mind.

[JeepFanactic]

I'll replace the fuel filter and see what hapens.  Does anyone think that it can be a sensor? Bought the truck as a project and to learn to do the work myself.

[Strokermjcomanche]

Rent a fuel pressure guage at your local parts store and check the fuel pressure . Iirc should be 31 lbs with the vacuum and 39 with it disconnected from the fuel pressure regulator at the front of the fuel rail .

[JeepFanactic]

Rent a fuel pressure guage at your local parts store and check the fuel pressure . Iirc should be 31 lbs with the vacuum and 39 with it disconnected from the fuel pressure regulator at the front of the fuel rail .

Where is the fuel pressure regulator? Does anyone have a picture of it?

[Blue88Comanche]

Check out this thread http://comancheclub.com/topic/12565-permanent-fuel-rail-pressure-gauge/

 

I added it to a renix MJ, the gauge is at a different angle but it is still readable.  

 

front     (Edit: the fuel pressure regulator is centered in this pic, it is attached to the fuel rail. on the left side it has a vacuum line, the right side has the fuel return line)

 

Drivers side

[JeepFanactic]

Thanks alot Blue this really helps out

[JeepFanactic]

Did a tune up to the MJ this weekend plugs, wires, fuel filter, cap and rotor it runs alot better but still sputters a little bit going from 1st to 2nd when I feather the gas when I get on the gas it runs great.    Havent been able to check the fuel pressure yet but I'm thinking it has to do something with fuel pressure.  This is my first Renix engine so I don't know how it should perform I have a 98 XJ that feels totally different when I drive.  It feels like  the extra horsepower in the 4.0 HO really makes a difference.  Does anyone have a opinion on this.