Two_Noodles

I have a puzzle I need some help with.
I have a 1994 3.0 3vze that will start fine, then slow down and stall after about 5-15 seconds. If I press the accelerator, the rpms climb normally to 3-4000, but I can't keep the engine going even at high rpm.

I replaced the fuel filter: no change. There are no engine codes stored.

I figured it may be the Throttle Position Sensor or the Volume Air Flow (VAF) meter (and it may still be) Both check out near what the (Chiltons) book says (well actually I thought the TPS was fried until I found the factory test procedure, I have a new uninstalled TPS if I need it.)

I can get the engine to keep running at idle by removing the air cleaner assembly and keeping the VAF halfway open with a rag. It idles up fine when I do this, but immediately dies if the accelerator is pressed.

Any ideas? I know just enough to be dangerous here.
Thanks.

thook

Find the fuel pressure regulator on the driver's side of the engine towards the front end. It's mounted on the fuel rail. Locate the little vacuum line and pull it off after the engine runs and dies. See if there's fuel in it.

If not.....

Find the diagnostic port...the little grey box with the flip up lid near the main fuse box on the pass side fender. Locate the terminals FP and B+ noted by a little sticker under the flip up lid. Take a wire and bridge (short) the terminals. Try to start the vehicle and see if it will continue to run......WITH the filter box/airflow meter installed.

Two_Noodles

Forgot to mention I replaced the fuel pressure regulator with another I had (no change, and no fuel out the vacuum line that I remember). I will try jumping the FP and B+ to see if that keeps it running.
Thanks

Two_Noodles

I had a chance to test it last night. With the FP jumpered to the B+ and the air cleaner assembly installed the truck ran fine. Idled up, and accelerated normally. Pulled the jumper back out and it stalled immediately.

This means I need a new VAF meter right?
At this link:
https://www.yotatech.com/forums/f116...k-3vze-187741/

I found the following "
VAFM - Volume Air Flow Meter - what the 3VZE has instead of a mass air sensor. It's the big metal thing attached to the air filter housing. It contains a trap door-like vane that measures the air flow into the motor. It has to open some to close a ground for the relay that controls the fuel pump. No air flow, no fuel pressure. It also measures intake air temperature."

So...the ground was not closed for the fuel pump relay. If I stuck a rag into the VAF it closed the ground to the relay, or if I jumpered the fuel pump it would operate.

TNRabbit

Or, it could be on the wiring haness near the VAFM.

Two_Noodles

Can it be the wiring harness? The fuel pump (and truck) ran when I jammed the VAF halfway open.

TNRabbit

Is it possible you have a hole in your intake tube?

If not, then that leaves you with a VAFM that has a bad spot in the sweep.

Mattie12

I just had the same problem with my 3VZE. Not knowing what was inside of the meter I decided to cut it open. I had a bad connection on the computer board in the meter. I got it to work, but I also found one in a salvage yard for $40. Those things are pretty pricey.
Runs great now. I probably needed the fuel filter anyway.

thook

You should test the AFM with an ohm meter, then. Or, test for voltage at the ECU by probing the back of the connector. At the ECU, you could rule out any wiring problem. There's a sticky on the front page of the forum with online manual links for the specs.

Testing at AFM>>http://personal.utulsa.edu/~nathan-b...92volumeai.pdf

At ECU>>>http://personal.utulsa.edu/~nathan-b...92volumeai.pdf

The FC circuit is the one you are concerned with. Good luck!

sb5walker

Sounds like the fuel pump switch in the air meter isn't making contact. If you tested that electrically, and it tested okay, then there is probably a crack in the air hose that goes from the air meter to the throttle body, allowing air to be sucked into the engine without going through the air meter and triggering the fuel pump switch.

Two_Noodles

Replaced the VAFM with a salvaged one yesterday. The problem persists, it would still stall after 5-15 seconds. I couldn't find any large leaks in the air intake tubes. There are a couple of tubes that could use a hose clamp, but nothing big. I will clamp those down, but they don't seem large enough to bypass the air intake. I will test the signal at the ECU next. Thanks.
I was able to drive the truck with the Fuel Pump jumpered at the diagnostic port, I don't think this is a viable long term solution though.

sb5walker

Driving with FP jumped will work - the fuel pump will run whenever ignition is on. But it is dangerous to do so. The reason for putting the fuel pump switch in the VAFM is to shut off fuel if the vehicle is in a collision. You don't want high pressure fuel to be pumped into the engine compartment and creating a fearsome inferno that could burn you to death.

If the fuel pump works when starting, and then shuts off when you release the ignition key, then either you have a bad COR, a bad fuel pump switch in the VAFM, bad wiring between them, or a leak in the air hose or elsewhere in the intake. If the motor runs okay when you prop open the trap door in the VAFM (be certain your "prop" cannot be sucked into the engine!), then your wiring and COR are fine. Either the fuel pump switch isn't activating when the trap door is only cracked open (as it is at idle), or there's an air leak.

FuelforWar

have you tried just cleaning all the contacts and parts within some of these components. my truck was running horrible once due to just gunk in the air intake assembley. pulled all the screws out of the bottom of the vafm and cleaned it all. ran great afterwards. perhaps clean the contacts to the wire harness too?

keithdphan

have you tried to set you idle higher so it wont stall, via the idle screw?

thook

That's not going to help at all if the fuel pump stops running.

moriverrat

So the final fix was..........?

stroker393

I'll second that. We all at one time or another have had the issue of a "no start" as I do now. I have read thousands of posts that are clearly following my same issues but they never end with "and my fix was" . Give us some more info about how you got your truck back running.

Two_Noodles

I didn't do the ultimate fix yet. I still suspect a broken wire between the VAFM sensor and the ECM. I have been running with the fuel pump jumped, which is a bit dangerous but it has been working. Thanks for the reminder though, I need to fix it correctly one of these days.

scope103

Try to get "one of these days" to happen before you have an accident and disappear in a ball of flame.

P51warrior

This has been a wonderful fix for me! Thanks to THook and the others who contributed. My 3vze decided to stop stone cold on the highway 4 hours from home and I naturally thought it was the coil or ignitor since I had no spark. I got a tow to Advance Auto who had the coil I thought I needed. After the new coil brought no life to my runner I ran out of options and retired to the hotel and my girlfriends IPad where I knew I could find Yotatech.com! Anyhow, after I tried the ignitor Advance overnighted to their store for me, and that provided no spark, I resorted to checking the VAFM with a borrowed multimeter. The distributor and other things tested just fine but not my VAFM! Voila! I tried the jumper wire in the diag box and I heard a welcome sound —the fuel pump!! progress, and it fired for a minute. Some more checking and the after securing the jumper wire in the diag box better I was able to get it running and returned the borrowed items from Advance, called my girlfriend and made it home for my afternoon shift!! All better now and the jumper wire is removed as I don't need it and all it's safety concerns.