I've recently did a head gasket replacement in my 94 4runner 3.0. I had it started after installing and ran great till a gas line broke about 3 to 5 minutes into running. Ordered new gas line, fuel filter, and went ahead and installed all new o rings on injectors too.
Put it back together and wouldn't start at all. Had spark and fuel. Originally codes 24 and 31 came up and the flap inside the vafm wouldn't move at all. I got the flap to move then only code 32 was showing.
I could jump fp+ to b+and get it to run but it ran horribly. If you increased rpms to around 2k the engines rpms would just jump up and down and if I let off the throttle it would just just stumble and stall. Would the VAFM cause all of these issues? I tried ohming the VAFM and I got overflow on all tests. Any thoughts ideas? Thanks.

 

I would expect a VAF with all open to the connector to cause these issues. (I'm assuming on your meter that "overflow" means open (infinite resistance)). If the flap wouldn't move, it sounds like a mechanical issue. Getting the flap to move with brute force isn't certain to help matters.

By any chance did anyone remove the connector screws on the VAF? All open sounds like the internal connections are broken. Removing the connector screws (and then pulling) is likely to do just that.


There isn't much you can do now that will make matters worse, so I would be tempted to remove the black cover and try to repair the broken connections. At worst, you'll have to pick up a replacement VAF, which is pretty much where you are at now.

 

I did open the top of it. That's how I got it to open. It was hitting a contact inside that wouldn't let it open. I bent that contact slightly and it cleared it. That's when the 24 and 31 code went away then 32 came up. I used this document I found here in the forums to test the AFM and yes everything stayed open. My father disconnected the VAFM while I was getting parts to make a bracket for it since it has an aftermarket intake and it wasn't bolted down or supported in anyway previously. He won't admit to it but I wouldn't put it past him to have taken the screws out to try to disconnect it.

 

Yup, those are the correct tests. And you can see from the given parameters, and the schematic, that "infinite" resistance is not good.

But before you buy yourself a new VAF, try one more thing. It's hard for me to imagine how you could break a VAF so perfectly that you get infinite resistance on every pin. So set up your multimeter again and try measuring some random resistances (or even just continuities). Just to make sure you're using it correctly.

 

Already done. I use the meter everyday. Tested with my wire sorter. Would the VAFM cause the rpms to fluctuate up and down? I tried opening the valve while the truck was running and the rpms would still fluctuate up and down when it was above idle rpms. BTW scope, thanks for the help on the injectors o rings from my previous post. They worked out good and really needed them

 

Then the only thing I can suggest is open up the patient and see if surgery can possibly help it.

 

Well looked at it closely this morning. It appears the screws must have been taken out and pulled on. The solders of the connector were broken if of the circuit board. Unfortunately the board is damaged to bad to be able to resolder it. Off to find one at the junkyard.

 

Feel free to post a picture. I'm not going to open up mine as long as it's working, and I'm always curious what I would find.

 

I was able to get a vafm at the junkyard $30! Yay!

I put it on and it started up but the idle is extremely low. It'll sit at 500 rpms for a little bit then stall out. It'll throw a coffee 52 (knock sensor) when it stalls. No codes when it's running. I've adjusted the idle screw and no change. It seems fairly smooth if I hold the throttle around 800. All vacuum lines are on as far as I can tell. When I'm holding the rpms @800 the timing is at 12 btdc. Any ideas now?

 

Here you go scope.


This is what happens when you take the screws out of the VAFM

 

Code 52 is thrown when the ECU "loses contact" with the knock sensor. It should then dramatically retard the timing to avoid damaging the engine. I wouldn't expect that to cause a stall, so you may have a knock sensor issue and something else.

Code 52 is most often caused by a bad "pigtail" from the knock sensor itself to a connector just on the other side of the lower intake manifold. The sensor itself is very tough. Unfortunately, you still have to get to the sensor to replace the pigtail, which means digging pretty far into the engine.

If you have room, I'd hang onto that old VAF. For $30 (wow!) it's not worth fixing the old one, but someday someone might need one when they are no longer easily available in salvage yards. Yours broke so cleanly it might be repairable.

 

The check engine light doesn't come on till it's stalling out. When it's running there's no lights. It only comes on when it stalls. Doesn't make sense. It has a new knock sensor and pigtail that I installed during the head gasket because of all the threads I read about it. I'll test it to see. I'm going to check the TPS too even though I haven't touched that at all.