rdhill

Mandatory truck info:
'94 4WD Xcab
3.0 w/manual tranny
NWOR headers and 2 1/4" exhaust system, magnaflow muffler

About a 18 months ago, I parked my truck for some needed maintenance. The main task was to rebuild the front end. While the control arms were off, I installed a set of NWOR headers. I also had leaks on both valve covers. While the intake plenum was off, I sent my injectors to WitchHunter to have them cleaned and tested. The intake plenum was hot tanked (after removing everything of course). The throttle body was cleaned. I replaced the plugs, spark plug wires, PCV valve, O2 sensor, and all associated gaskets. The entire exhaust system is new -- headers to tailpipe.

After getting the rest of the exhaust system installed, the truck ran OK for a while but wouldn't idle -- to high. Crunched for time, I took it to the Stealership where they replaced the throttle body. I was pretty sure that it was the throttle body due to the excessive play in the shaft that I found after cleaning it. It wouldn't allow the throttle to close completely. The new throttle body worked like a charm. It ran great! I drove it for almost a 1000 miles until......

About halfway across Wyoming, it started having some low power, hesitation and stumbling issues under 3000 rpm. I replaced the cap and rotor in Colorado but that didn't help. Upon reaching the new home in Alabama, I started troubleshooting. I checked the resistance of the VAFM and O2 sensor as described in the FSM. The resistances were all within the range specified. Old posts on the forums suggested a new EGR and O2 sensor. Since the O2 sensor was a NAPA special, I was suspect of it. I replaced both with new parts from the dealership. It runs better but still has the low power and hesitation issues uner 3000 rpm.

Yesterday, I pulled the ECM from the quarter panel to gain access to the connectors for testing. Following the FSM, I checked the voltages across the various specified connections. Here is what I found:Those values are within specified range. Here is where things get interesting:
The IDLING value is about HALF of the specified voltage. That harness looks good. I have tried jiggling the harness at the VAFM connector without any change in performance. If I manually deflect the flapper in the VAFM, the engine will change performance. At a certain point, the idle does change and becomes more stable. Pushing it too far, and the engine leans out and dies. Pulling it closed, a carbon soot is visible in the exhaust and the engine will eventually die. It appears the ECM is working.

Before I replace the VAFM, does anyone suggest anything else?
Does anyone concur that the VAFM is bad?

Thanks

Targetnut

go back and test the voltage across VS-E2. this time with the key on slowly sweep the measuring plate from closed to full open.

the voltage should progress steady with no spikes or dropouts. An oscilloscope is best for this, but if you go real slow you should be able to catch a problem with a Voltmeter. If the tests OK then look elsewhere.

I think you should test the fuel pressure and delivery volume. What you are describing could be low fuel supply causing a lean condition under load. If the volume is low replace the fuel filter first. Leaving a vehicle to sit for an exteded time is an invitiation for fuel supply problems.

Hope this helps.

rdhill

Thanks, I'll check things out again. I don't think that the voltage cheanged until we hit the 3000 rpm point - stayed 1.4 VDC. I'll recheck though. The resistance did change as I swept the gate though. It would climb and then drop in a square wave pattern as the manual suggests.

I had to order the appropriate banjo to schraeder valve fitting for my fuel pressure tester. Should be here in a couple of days. In the meantime, I am going to jumper the fuel pump ON on the diagnostic port and see if that makes any difference.

Thanks again.....

rdhill

I finally recieved my banjo fitting from Actron for the fuel pressure tester. The fuel pressure with the fuel pump ON (jumpered on the diagnostic block) is 41 psi with the engine OFF. At idle with the vacuum hose ON the regulator attached there is 37 psi of pressure. At idle with vacuum hose OFF the regulator there is 41 psi of pressure. The pressure does not fall below 21 psi for about 7 minutes after pump is turned off.

The fuel pressure is within specs, any ideas now? I'm still thinking it's the VAFM.

rdhill

It now looks like I had two problems. The VAFM was bad. Also, the TPS needs to be adjusted. I installed the new VAFM last night, and the hesitation went away but it still was acting like not enough fuel was getting to the motor. I unplugged the TPS and wowsa! We had power again.

I suspect that the TPS was not adjusted when the stealership replaced the throttle body. One it warms up today, I'll head out to the garage, pull the throttle body and do the alignment.

rdhill

The TPS was way out of adjustment. After an adjustment, the truck runs great. The idle switch didn't throw until the throttle was fairly open. This explains the why the engine wouldn't run well until the magic 3000 rpm switches engaged. Anyone care to chime in and discuss what the timing does at 3,000 rpm?

ozziesironmanoffroad

not sure what it does, but glad you got it workin good

PoleVaulter95

thank you for posting this thread. my engine just seems lost below 3000rpms and come saturday the vafm and tps will be gettin a look at. cant wait to hear what people have to say

rdhill

I would definitely check the TPS adjustment first. I did the continuity check before I adjusted it. With a .020" shim the idle switch should be on and with a .031" shim the idle switch should be off. Mine was set incorrectly so I changed it. I'm beginning to wonder if the new throttle body needed to "break-in". Then again the screws holding the TPS down weren't very tight -- they are now.

jht3

which one? i believe the M12x1.25 adapter is the correct one, but i've also seen reference to M8x1.0.

rustypigeon

I was going to ask the same question. I think it is a 8x1.0 for the 22re. Not sure about the 6 clyinder.

jht3

the manual for the Equus tester says m8x1.0, but lists m12x1.25 as an alternate. they don't say which fitting those refer to though, and i saw another thread on here where someone apparently attached a m12x1.25 banjo adapter to the front fuel rail, like the FSM says.

bugs1961

I have never encountered an 8x1.00 thread on a Toyota. The majority of bolts and nuts will be 8x1.25 or 6x1.00.

sb5walker

They're talking about a fuel injection fitting, not a regular bolt. There is no 8x1.25 fuel injection fitting that I know of; the 8mm banjo bolt fitting is 8x1.0. I'm not sure whether that is the correct fitting for the 22re & 3vze, but I think so. It would be nice to get confirmation from someone who knows.

http://www.actron.com/product_detail.php?pid=16288