Multi-Port vs Throttle Body Injection to upgrade the 258

[Linus]

Good afternoon, I am considering changing my CA legal Carter BBD carb out with Fuel Injection. I have a relatively stock 258 (mild cam, header) and have had a very hard time keeping the mixture right. Anyway, it looks like there are three options: Either a Howell or MOPAR TBI, and a MOPAR Multi-port Injection. A lot of folks seem happy with the Howell, but I haven’t heard anything about the Multi-port injection. Looks to be about a grand more than the TBI. Is anyone running it, and is it worth the extra cost and complexity?

Thanks in advance for your opinions/experience.

[SAR Jeeper]

I have the Howell. Cost was the major factor. I have been very happy with it. I had some initial bugs that I worked out, and its running great. I'm getting 16 MPG on the highway, running 35" tires and 3.73 gears. After sitting for about two weeks, I crank it over, and it fires right up. No more pumping the gas like before!

[Mitch]

Mark,

I switched to the Howell TBI when I replaced my 4.2 Other than a cold start issue (runs rich till warmed up) It has performed great. Instant throttle response and it has NEVER stalled, reguardless of the angle or situation! The Howell added a few horse power and really cleaned up the engine compartment.

Mitch

[ECV Jeep]

I am running the MPI kit on my 258, and I love it. I don't know if it is worth the extra money or not, as I know alot of folks wthat have had great luck with the TBI kits. My engine puts out an awful lot of power for a 258, but I have also switched to a 4.0 litre head and headers and all that jazz. As for problems, I have never had ANY with this kit to date.

[Linus]

Thanks for the input,

Sounds like either would be a big improvement over the Carter. Just need to find an inexpensive MPI kit.

[Ol Man]

I installed the MPI conversion back in 1998 on my 1985CJ. I think it is a good system. I also know the Howell system is good and less expensive. The Howell was not CARB legal at the time.

For the MPI system I would recommend carrying a spare Throttle Position Sensor (TPS). When it goes you cannot start the vehicle and it may run rough before failure. One way to get off the trail should it fail, is to get the engine started by either getting some gas in throttle body or even use starter fluid. I was able to get off the trail doing that.

For the KOH race, the TPS sensor also would not allow the auto trans to shift in Richard Gauthier's XJ. His was the older FI setup, but may also be an issue with autos in the newer ones. We took and transferred a lot of parts before figuring that one out!

Talking about autos, another sensor to carry if you have an auto (at least later TJs) is a neutral start switch. Ran into that one when one of our guys' drive shaft bolts loosened and the drive shaft damaged one pretty severely. It would not allow it to get out of park. Ended up pulling the drive shafts and pulling him back to the trailer.