I'm hoping there is someone out there that can assist me with
troubleshooting a problem that I am having with my 1996 Tacoma. When I
rev the engine up to approx. 3000 RPM (I've tried both running it up
quickly and creeping up on that speed) it begins to sputter and shake
followed immediately by a loss in RPM. The engine starts easily and
idles normally.

Vehicle detail:
'96 Toyota Tacoma
2WD Extended cab
2.4L I4

Here's what I've done so far (many of these steps I found in my Haynes
Repair Manual):
- I received a check engine light once while revving up. I used a
code reader to view the code: P0100 (Mass Airflow (MAF) sensor error
circuit). The code has not returned since the first time, and I have
received no new codes.
- I tried checking the voltage of the MAF sensor per the Haynes
instructions. I did see voltage fluctuation when air blew through the
sensor.
- A friend suggested that I attempt to clean off the hot wires on
the sensor. I used some electronics cleaner that should leave no
residue.
- None of this had any effect, so I tried a brand new MAF sensor.
I also looked for a loose wire at the plug which connects the sensor.
- Still no luck, so I started testing the fuel system. I began
with the fuel filter, because I hadn't changed it since I purchased
the truck and it was WAY overdue anyway.
- Next I connected a fuel pressure gauge and found the pressure was
48psi. This pressure stayed fairly constant even when I revved the
engine past the stuttering point.
- The 48psi level was higher than the specifications listed in the
Haynes manual, so I then checked the fuel pressure regulator. I hooked
up a vacuum pump up to the line that feeds the regulator. The fuel
pressure dropped as I increased the vacuum on the regulator.
- I tried revving the engine up while I had the fuel pressure
lowered to within the range specified in Haynes. It still sputtered.
- I hooked up the vacuum pump up to the other end of the fuel
regulator vacuum hose to see if I could read the vacuum created by the
engine at that point. I never received any vacuum.

I haven't yet checked for vacuum at any other points. I wanted to
check with the experts before I go further. Does anyone have
suggestions of how to diagnose this problem and/or refine the steps
I've already taken?

Thanks in advance for any help.

You might want to read this. I have a similar problem on my '96 T100 with
the 3.4 engine and I suspect this might be the cause:
http://www.motor.com/MAGAZINE/Pdf/012007_04.pdf

Wormsign off

"super_dave_42" <super_dave_42 (AT) hotmail (DOT) com> wrote