I've been an unregistered "lurker" in this forum for years and consider it to be a first rate resource for Toyota Tacoma information.
This is my first post and I'm hoping that I can get some insight on what the issue with my Tacoma might be.
2002 Toyota Tacoma SR5, TRD
3.4L V6 Engine
Truck has Factory Alarm & Cruise Control
No modification done to Truck other than the audio system and K&N Replacement Air Filter.
When accelerator is depressed, RPM increases to about 2,500 and then it will sputter.
If throttle is opened all the way, engine will backfire through the intake.
If fuel return hose is restricted, the problem goes away.
Truck has had check engine light on for quite some time now but runs fine and gets same gas mileage. (19 mpg average)
Error Codes present prior to new problem arising = P0171 System too Lean (Bank 1)
Current Error Codes = P1135 Air/Fuel Sensor Heater Circuit Response. (Bank 1 Sensor 1)
Immediately prior to issue presenting itself, I was troubleshooting and eventually located a cross short between the lighting and brake light circuit.
This cross short occurred inside of the dual filament bulb inside the tail light cluster.
(One filament blew and subsequently welded itself to the post of the other filament.)
The cross short caused the brake lights to come on when the head lights were energized.
It also caused the instrument lights and the marker lights to become energized when the brake lights were activated.
Troubleshooting Steps already taken:
In accordance with Toyota Factory Service Manual DI-242 (Problem Symptoms Table), I started troubleshooting the fuel system by following DI-448.
While doing so, I noticed that if I pinched the fuel return hose while manipulating the throttle butterfly, the acceleration symptom would go away.
This led me to believe that the fuel injection system was not getting enough fuel pressure to operate properly.
Starting with the easiest item to eliminate, I replaced the fuel filter. (No Joy)
The next logical culprit in my mind was the fuel pressure regulator.
I needed to replace the valve cover gaskets anyway, so I changed the regulator. (No Joy)
The only items left in the fuel system were the fuel pump and all the plumbing.
I replaced the fuel pump and the hoses between the fuel tank & hard lines. (No Joy)
As most of you know, the service that I have already performed is quite time consuming and has parts that aren’t exactly cheap.
So, I come to you all with my heart in my hand, hoping that one of you is able to help me resolve my problem.
My thoughts at this point in time is that I either have a partial obstruction in the fuel system or an electrical / electronic problem that is preventing the fuel pump from putting out the necessary fuel pressure or the ECM from operating properly.
Since the symptom was not present prior to working on the electrical problem, I’m inclined to lean toward an electrical / electronic issue.
To take the electrical wiring to the fuel pump out of the equation, I disconnected the power to the fuel pump and connected a “Jump Box” directly to it. (No Joy)
Since replacing the ECM is quite expensive and also not a returnable part, I want to exhaust all other possibilities prior to going down that road.
Any thoughts or suggestions are much appreciated.