About a month or so ago I purchased the Ballistic Fab Taco. Jeff and the crew had swapped a 3.4 into the rig and it was running fine when I took delivery of it.

About a month ago I took it to a local shop to have the emmissions equipment put back on, so I could register the rig and make it "some-what" street legal (this is a stretch for sure).

Here is the problem: When I first picked the vehicle up from the mechanic it seemed to be running fine. I headed out to the emission test center just about ten miles away. Just before I got there it began to sputter just a little bit; I thought maybe it was getting low on gas. At the emissions they rejected the vehicle on visual inspection for the exhaust, so I headed back to the shop.

The sputtering started to get worse and about four miles from the shop (100 ft in front of the gas station) the rig died. The guys ran out and determined the fuel pump had died. We swapped it out and it fired right up... but it was still running really rough. Any thing over half throttle and it acts like its either not getting enough fuel or it's misfiring.

They replaced the new fuel pump with another just to make sure and the same thing occurred.

Here is what had to be done for emissions:

- The custom fuel cell was leaking and could not be repaired so it was replaced. A 19g RCI unit was used which required using a different fuel pump (external vs internal). The shop put on a 70-80PSI pump; the engine requires about 35PSI, based on what I've personally dug up.

- A new CAT was installed and a new O2 sensor with a new 4 wire connection back to the harnes was added. I'm not sure that the O2 sensor is a Toyota part; it may be a universal. Prior to that there was no CAT and a one wire sensor was used and tied into the harness.

- The EGR valve was added back in. It also looks like the Vaccum modulator was added back in, but it doesn't appear to be tied in to the EGR with the vaccum switch, so I'm not sure what's going on with that. To eliminate this from the equasion we blocked it off and the problem still persists. When I took delivery of the rig from Ballistic, the EGR was blocked and the engine ran just fine.

- The Charcoal canister was added back in a tied into the tank.

The only two things I can think of are Fuel Pressure Regulator and ECM. I don't know if the higher pressure fuel pump would eff with the FPR or not. I'm also wondering if the new O2 sensor is sending a shit signal back to the ECM.

Any ideas?

Wow, I would have to assume all the obvious things have been checked. The only part of your question I can answer with certainty, is checking the o2 sensor. Use a volt meter to see if the signal is making its way back to the ECM. Also, were all the connections made at the ECM soldered? A bad connection anywhere in the emmissions system can cause the problems you are having. Also, in regards to that, URD sells an O2 simulator that may fix that problem, but once again, make sure all the connections are soldered.
From what I know of the FPR and dealing with the S/C issues over the years, is that a lack of pressure is usually the problem. My gut instinct says too much pressure should not be an issue. That is, after all, what it is supposed to do.
Have you put a scan tool to use? I am sure there are stored codes that might be of some assistance

What about on the other end? maybe the MAF is going? MY TJ had that issue and it would begin bucking and lurching once in awhile when the airflow wasn't being regulated properly?

What about on the other end? maybe the MAF is going? MY TJ had that issue and it would begin bucking and lurching once in awhile when the airflow wasn't being regulated properly?

The timing of the sputter seems to be related to something that was touched during the emissions rebuild... I had the rig on the road everyday for about a week before taking it in and it ran out fine under full load. It's not impossible, but I'm going to be really suprised if it turns out to be something outside of the stuff that was tweaked during the work... It's worth checking though.

Wow, I would have to assume all the obvious things have been checked. The only part of your question I can answer with certainty, is checking the o2 sensor. Use a volt meter to see if the signal is making its way back to the ECM. Also, were all the connections made at the ECM soldered? A bad connection anywhere in the emmissions system can cause the problems you are having. Also, in regards to that, URD sells an O2 simulator that may fix that problem, but once again, make sure all the connections are soldered.
From what I know of the FPR and dealing with the S/C issues over the years, is that a lack of pressure is usually the problem. My gut instinct says too much pressure should not be an issue. That is, after all, what it is supposed to do.
Have you put a scan tool to use? I am sure there are stored codes that might be of some assistance

Haven't put a scan tool on it yet but it's in the works; gonna need it for future use so I might as well break down and get one.

I had looked at the URD O2 simulator as I'm beginning to collect some data for a S/C install. Would like to get it to work properly in this config without it if possible, as it was working good before and should work okay without it... BUT if that's what it takes...

I'll double check the O2 connections for starters and see what I come up with. Appreciate the input.