Engine Howell 4.2 TBI ongoing idle and WOT fuel issues with new system

[CJKen51]

Hello All, I have around 1 hour of actual drive time on my Howell TBI it ran "mostly" well to begin with and I was excited to drive it. Then, it just started leaning out and dying. Was towed home, by my son, that day. That was back in early June. Anyway, I've messed with this forever. The list of tests is a long one.
When I unplug the MAP sensor, it will actually idle. It idles smooth. Granted, it's rich and in a limp mode, which lines up with the service manual that was included in my kit. Plug the MAP back in and back to dying within just a few seconds. Here's the kicker: I've tried two different MAP Sensors. I also picked up an extra computer, since they were $95. Tried both of those and switched the PROM over, of course. I've talked to Troy, at Howell, 3 or 4 times now and I checked and verified everything he asked. Looking for a tip on anything else I could check. Thanks, in advance.

 

[CJKen51]

Thank you very much. I did talk to Troy about this. He said there was an issue with the distance suggested, and had me cut the hose real short and plumb directly off the barb fitting (back of TBI) didn't make a difference. Any help is appreciated and i'll keep trying different hose lengths. Both MAP sensors react the same way, too.

 

[Placer Jeep]

Thank you very much. I did talk to Troy about this. He said there was an issue with the distance suggested, and had me cut the hose real short and plumb directly off the barb fitting (back of TBI) didn't make a difference. Any help is appreciated and i'll keep trying different hose lengths. Both MAP sensors react the same way, too.

Make sure your ECM is grounded.

 

[Belizean]

What does the Howell use for an O2 sensor ?

 

[KRUPP]

Troy had me shorten the vac hose for the MAP sensor as well. Seemed to help a little bit. New injectors were the eventual fix though.

According to the information in my Howell kit instructions, the O2 sensor is a Single Wire General Motors PN 25155816
or Heated Sensor General Motors PN 25312184.

 

[TSB8C]

Use the heated sensor. My first attempt at EFI on a prior CJ5 had a single wire O2 sensor that worked just fine until it got wet driving in the rain. Cooled off and started throwing errors. Once dry and warmed back up, all was well again. Mine was mounted in the collector portion of a fenderwell exit header on one side.

 

[CJKen51]

It's a single wire o2. My o2 goes into the exhaust manifold, from a 81 & up exhaust manifold. I also have a bung welded/plugged, further down the exhaust pipe. I'll experiment with that one. Concerning the ECM grounding comment, do you mean to ground the housing itself, in addition to the pin that's grounded through the harness? I do not have the ECM case grounded.

 

[CJKen51]

Howell TBI follow up:

Hello all, had to step away from the project for a few months. Like KRUPP, mine was dirty injectors. Runs very well now!!
Lessons learned:
1. The Howell kit comes with one fuel filter. It goes in line before the fuel pump and is designed to protect the pump. From what I can gather, it's around a 100 micron filter. DO ADD a second, 10 micron filter prior to the Throttle Body, (after the fuel pump) to protect your injectors.
2. When installing a Howell, after having a carburetor, REPLACE the fuel return line before you try to run it! Once your TBI is connected, whatever junk that was in the return line will now be in your tank. I had cleaned my tank very well, prior to the install. After running the TBI and driving issues happened (almost immediately) I dropped the tank and it was full of dirt & debris again. Some of this made it to the injectors.
3. Consider replacing your fuel tank, at the same time, if yours is 40+ years old. I replaced mine, as the new plastic MTS tanks make a better seal to aftermarket fuel sending units than the original tanks do. And, you're starting with all new, clean fuel system components.

I appreciate everyone's help while I worked through this!
P.S. I picked up a $AMC 150 smoke machine from Amazon. It's one of the most valuable diagnostic tools you can own and can be used on all EVAP system DTCs, exhaust leaks etc.... happy trails.