JJGADU

94 Toyota Pickup 22RE starts up fine but quickly dies. Runs as if there is no issue when VAF/AFM flap is held open manually.
Tried another OEM VAF/AFM with same results. Possible that both units are faulty? Could it be something else? COR?
What can be ruled out?
The issue started after I had hosed the engine bay and cabin down, and reinstalled parts like the VAF/AFM, coil and igniter, and ECU. I blew most of the harness and connectors out with air and electrical contact cleaner, but maybe I missed some?

scope103

Welcome to YotaTech.

Why is it that the engine sucking air won't hold the flap open? The electrical seems to be working correctly, so I wouldn't bother the COR or fuel pump.

You're not trying to run the engine with the induction plumbing disconnected, are you? If you just got here from the 1970s, you might be used to working on your carburetor with the air cleaner sitting on the bench. Can't do that with a fuel injected engine.

JJGADU

Induction plumbing is completely assembled. As long as I hold the flap open, it will run with the VAF/AFM connected to the air cleaner with the outlet disconnected from the intake tube/pipe, or detached from the filter while still connected to the intake pipe, or with it totally separated from the intake.

RJR

Someplace you're leaking air around the VAFM. All the air that the engine uses must come through the VAFM, or it won't run properly (or at all). No short cuts or alternative paths allowed.

JJGADU

I don’t see any cracks and all the clamps are tight. But I will go over it again.

Apart from the intake plumbing inbetween the VAFM and throttle body, where else should I look for leaks?

JJGADU

Disassembled and reassembled intake system leading up to throttlebody and it still isn’t staying on. Then I disconnected the VAFM from the air cleaner and propped the flap to stay open to keep the engine running. Sprayed throttlebody cleaner over all the hoses to catch a change in idle but didn’t get anything. Only time the idle dropped was when I sprayed right at the VAFM inlet, but that was a given.

Anything else I should look into?

Trying to get another VAFM, this time directly from a currently running Pickup.

RJR

Does the vane on the VAFM move freely? If it's sticky maybe an idling engine doesn't move enough air to pull it open. Not sure I believe that could happen, but it's a thought.

JJGADU

Vane is not sticky.

I just came from testing the 2 VAFMs I have on a running truck and they both worked fine. So that would rule out the VAFM as the culprit. I also tested my air intake plumbing on the same truck and they too checked out okay.

Any other suggestions?

scope103

Do you have any other "air" lines left open? Resonator, PAIR, EGR, A/C Idle-Up, ... As RJR says, it's not enough that air is getting into the intake manifold. It ALL has to go through the VAF.

JJGADU

No air lines left open. I never touched any of the vacuum lines cause they look pretty confusing, left them all as is from when the truck was still running.

So it seems like air is the issue. But let me get this straight.. There must be a big enough leak or open air line that the throttlebody is not sucking air hard enough to pull the vane open? Cause even if I open the throttle it still chokes and dies.

JJGADU

Idk why there would be, but, are there any vacuum lines that lead into the cabin? I did remove the blower motor box to get to some rust on the firewall/cowl. It was a tight squeeze getting it out and back in, maybe snagged something in the process?

RJR

Just to make sure we're barking up the right tree, short Fp to B+ in the diag connector. It should run without holding the vane open. Let us know how that test comes out.

JJGADU

Maybe I should’ve mentioned it before, but that was the first thing I did before even getting a second VAFM. And yes, it stays running as long as the jumper is in.

And I just checked the air lines again. They are all connected and have clamps securing them. And when I tested the VAFMs on a running truck yesterday, I did not secure the lines and hoses at all, but the truck still ran, air fuel ratios prolly off, but it still ran.

JJGADU

When the problem first arose, I even considered securing that jumper in there, but would not be able to sleep knowing that the real issue still exists. Plus risk flooding and fire.

Paul22RE

Why did the ECU need to be reinstalled? How long does it run before it dies?

JJGADU

I had to clean up and seal some rust holes, then washed everything down. It would run for a second or two then shut off.

RJR

Well, it's pretty clear from everything that you've told us that the engine is pulling an inadequate amount of air through the VAFM to hold the vane open and keep the fuel pump enabled. Question is, why is that? I can think of about three things, two of them bad. Either you've got a massive still unseen leak in the induction system, or your engine has jumped valve timing so badly that it barely generates any vacuum, or during the wash job you hydro-locked one cylinder and blew a hole in it, which is now providing an alternate air source to the other cylinders. With Fp jumpered to B+, is the truck driveable? Does the engine run smoothly and seem to be developing a normal amount of power at all rpm's? I have a suspicion that, while the engine might run with the fuel pump jumpered, it won't generate enough power to get out of 2nd gear.

JJGADU

So here’s a new discovery.. Jumped the fuel pump and power at the diagnostic port to get it to run while I sprayed the vacuum lines in search of a leak. I think I may have noticed an idle fluctuation when I sprayed in the fuel regulator area but ran out throttle body cleaner. Let the truck run while I looked around the garage for another can.. About a min or two into my search, the truck dies. Thinking the paperclip I used may have popped out from the diagnostic port, i reinsert and tried again. The can I decided to use was electrical contact cleaner but ran out beforet I could even find the leak, and again the truck dies after about a minute. I pull out the paperclip and try again, but now I can’t get the pump to turn on. I usually have a hard time finding the sweet spot for the two pins but would eventually get it. Now, when I’m sure the clip is making good contact, the pump still won’t turn on. Never experienced this before, or just never noticed.. But I’m pretty sure that it is not normal.

So I guess that’s one of two gremlins.. Next, if the pump still doesn’t turn on with the jumper in, I will disconnect the VAFM from the air cleaner and prop the vane open. Hoping it will stay running, I will go back to spraying around the FPR and find that leak.

Lmk what you guys think.

RJR

If you have a vacuum gauge available, I'd suggest (once you get it running again) connecting the gauge directly to a port on the intake manifold (not the throttle body) and measuring the vacuum. Should see at least 15 inches at idle.

JJGADU

I will look into using a vacuum gauge, never used one before, don’t think I’ve ever seen one either.

Any thoughts on the truck dying a minute or so after running with the jumper in? Or why it suddenly won’t turn the pump on with the clip in?

I believe an engine wouldn’t hold a pretty stable idle if there was a hole somewhere internally. For the minute or so that it was running with the jumper in, it definitely didn’t blow out any smoke or have a knock. Then again, just because it sounds smooth doesn’t mean it has power. Now that it doesn’t stay running long with the jumper in, I can’t drive it so I won’t know it it still has power. But when I did wash the engine bay down, I made sure that the throttle body had a towel and plastic bag over it.