EFI Air Flow Sensor

----------------------------------------------------------------------

Date: Wed, 13 Aug 1997 13:01:40 -0800
From: eric@qnis.net
Subject: *Mass airflow sensor modification
To: toy4x4@tlca.org

Howdy folks,

I just thought I'd pass along my experience with airflow meter modification.

I've been having trouble with a rough idle and terrible fuel efficiency
(15 MPG) since I bought the truck, a couple of months ago. (1986 4x4,
factory turbocharged- the motor is all stock, as far as I know)

With the help of Jim Brink and other regular contributers to this list, I
feel I've been thorough, but  I've been unable to find a fault to account
for my truck's poor idle/fuel efficiency.

I decided to open the airflow sensor to see what it looked like in there...
very straight forward.

I adjusted the internal cog about 7 notches counter-clockwise, after
marking the original setting.

Result:

1. Much smoother idle-

2. turbo seems to kick in quite a bit earlier, about 1800 RPM as opposed to
the previous, approximate
   2700 RPM-

3. Good drivability-

4. I seem to feel a bit of increased "off idle" torque too, but I couldn't
swear to it-

I made the changes only yesterday, so I don't know how the fuel efficiency
will respond, but I suspect  the mileage will be worse, I'll just have to
wait and see.

My impression:

Adjusting the cog CCW relaxes the coil spring responsible for resisting the
airflow being pulled through the meter; the adjustment makes the vane open
easier/further with the same amount of volume/force of air. This is only my
guess; airflow meter specifics don't seem to be readily available.

When I made the adjustment, the idle increased a bit.

I think the overall mixture, or at least the idle mixture, is richer now.
the reason I say this is because the pulse at the tailpipe is slightly
"softer" after the adjustment, not the nice crisp snap of a correct and
efficient air/fuel mixture.

I honestly don't think I fixed anything with this adjustment. I believe I
compensated for the real problem or problems.

I do know that #s 3 and 4 cylinders are about 125 Lbs. PSI, which is 25
Lbs. down as compared with cylinders 1 and 2. I'm thinking that I may have
a leak between 3 and 4... I guess I need to find a way to do a leak-down.
Does the 22RET motor commonly blow the gasket between cylinders?

I ought to mention that overall power has always been VERY good. Very
strong acceleration, after a bit of turbo-lag.

I'm going to drive my truck this way for at least a couple of weeks to see
what the fuel efficiency does.

While I'm generally not afraid to experiment with adjustments, I'm sure
Toyota, in their infinite wisdom and commitment to quality???, set the
airflow meter adjustments where they are supposed to be. If my truck isn't
running well, it's because there's a problem I haven't found yet.

I welcome ANY and ALL comments!--- I'm in digest mode, if that makes a
difference.


Thanks,

Eric Mewhirter (central California)

------------------------------
------------------------------

Date: Wed, 13 Aug 1997 08:15:10 -0400
From: john skaggs 
Subject: EFI Air vane mods
To: Toy4x4@tlca.org

Straight from the L.C. Engineering catalog.

The following adjustment can be used to richen or lean the air/fuel mixture from 
the factory setting.  The adjustment could be necessary when using the 
filtercharger; big bore throttle body or other EFI modifications, but it should 
never be performed on a "stock engine" because the computer will recognize the 
"error".  The mass air sensor is always found on the top of the air cleaner 
canister on Toyota Pick-ups and 4 Runners.  The sensor is an aluminum housing 
with a black plastic lid.  Cut the silicone seal holding the black plastic lid 
in place.  Use caution so plastic lid is not cut or damaged.  Gently pry the lid 
from the housing.  To adjust, first mark the original location of the hold-down 
clamp on the gear wheel so you can return to stock setting if necessary.  Loosen 
the clamp screw and rotate the gear wheel a few teeth (normally 3 to 5 teeth) as 
necessary.  Clockwise leans the mixture, counter clockwise richens the mixture.  
After the adjustment, make sure you establish a good silicone seal when 
replacing the top plastic lid.  Moisture can destroy the sensor.

Hope this helps, 

If you have questions for L.C. Engineering their ph# is (520)505-2501
Their catalog is available for $5.00 or free with purchase of product.
I have no connections with them.
I do not know if this material is copyrighted or not.

------------------------------

Date: Wed, 13 Aug 1997 15:15:48 -0500
From: "John Schultz" 
Subject: EFI Air vane mods
To: 

I may be way off base here but, on a diesel engine these symptoms occur
when there is an air leak somewhere in the injection system.   The
injection system can get temporarily "air locked" until it (the air) is
forced through the system.  Sometimes is in one line between the pump and
the injector (causing a rough idle at start up) or heaven help you if it in
at the pump itself (causing a no start no matter what).  It is usually
leaking at the injectors when this occurs but not necessarily.  Be
particularly suspicious of those portions of the system that are under
vacuum vs. those under pressure.

John

- ----------