ROCTaco

First I just want to say "hi"... I can tell this site is going to be invaluable for to me.

I've been a Jeep guy for quite a while (I know, booooooo), but always told my friends if I ever had to do it all over again I'd do a Yota, and I did. I recently bought a slightly modified 95.5 Tacoma that had a 3.4 swapped in. The rig ran great when I got it but had been off-road only for about three years and was void of any emissions equipment.

I wanted to get it registered and "plated" because some of the trails we run require crossing heavily patroled highway. I want to make the rig as "street-legal" as possible to keep the fines in check when I get pulled over (it pretty much begs to be pulled over).

Here's the problem:

I bought the rig a little over a month ago, got a temp registration and spent a week driving it around so I would know what the operating condition was before I took it into the shop (and yes the local police did pull me over but they were very cool about it all, pretty much they just wanted to check it out). Again the engine ran great, you could full throttle it and it felt really strong.

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 signal back to the ECM.

Any ideas?

Sorry for such a long first post. I have read through a bunch of the 3.4 swap threads but haven't come accross anything that really seams to shed light on the problem... Any input is really appreciated.

Here's a pic of the rig; the AZ guys will recognize it...

fillsrunner4

First welcome and sick rig dude!

I had a similar problem but my solution was a whole new motor AGAIN. Im going with the 4.3 froma chevy for easy and cost. Its an easy and cheap to fix up motor.

Not really to much help since I could never find why mine did the same stuff.

I replaced $$$ in sensors and misc crap and had no luck with it. Motor is too finicky for the trails IMO

Good luck with it

ROCTaco

Hey man good luck with the Chevota build... I'm going to stick with the 3.4 for a while and see if I can't make it work. I know the guys who built the rig had a lot of success with the engine and given the timing of the problem I'm prett sure its tied into something we just did. I'm leaning towards the 02 sensor and/or the wiring associated with it; that's where I'm going to start...

If I ever do decide to swap a new engine in, I've got a sweet lil all aluminum 3.9L Land Rover engine I can build up and dump in. Weighs just a tick over 300lbs fully dressed and should put out 350hp when we're done with it. But then I have to rewire all over again, so just me now.

From there I'll be doing a little

jasond

You might check the fuel trim on the data list. If it looks high (over 15%) then you might have a dirty mass air flow sensor, among other things. I use non-clorinated brake cleaner to clean them out - just make sure it is dry before you put it back in. You might also look and see if there is a hole or tear in the tubing going from the mass air flow sensor to the throttle body.

ROCTaco

I will definately check the mass out... the timing of it makes me think it related to the work we just did, but if we can't back out of it I'll know it's something else.