My 88 4runner with the 3.0 runs bad with the vafm plugged in. Pulled the spark plug wires one by one and cylinders 3 and 5 are not firing. they have spark. All cylinders have compression around 150. Cam and ignition timing look good. No trouble codes. When I unplug the vafm the engine runs good for a second then dies as expected due to the fuel pump not getting a signal from the vafm but if I unplug it and plug it back in before it dies a couple times I can get the engine to stay running good with all cylinders firing with it unplugged. Jumping b+ and fp on diagnostic port with vafm plugged in makes no difference but jumping them with the vafm unplugged makes the engine run even worse than with vafm plugged in. What is causing cylinders 3 and 5 to misfire with the vafm plugged in? Bad vafm, wiring, sensors, or ecu? Thanks for any insight.

 

Any progress???

 

one possibility is leaking injectors. When you unplug the VAF, the fuel pressure drops leaning out the over-rich cylinders. When you run the fuel pump with the jumper, they don't lean out.

You could try removing the spark plugs, letting the cylinders dry out, then putting a piece of paper in the cylinder. Run the fuel pump (jumper) for a few seconds, then pull out the paper. They should be dry.

 

Going to try a new vafm. Ordered one from napa. Just waiting for the email saying it is ready for pickup. I'll get a new multimeter for further testing if the new vafm doesn't do the trick. The one I have is acting up.

 

Thanks scope. I will try that.

 

The injectors are not leaking. I pulled the cold start injector as well. It is not leaking with the fuel pump on but it was pretty oily.

 

Napa couldn't get me the vafm even though it said online that they had one available for pickup. Looks like nobody carries them anymore. I can send mine to rockauto to be remanufactured which takes 2+ weeks so want to make sure mine is bad before I do that. New multimeter should be here tomorrow. This all started out of nowhere while helping my brother move. At first it would run good on a cold start then start running rough after it warmed up. Now it immediately runs bad (cyl. 3 & 5 misfire) even from a cold start. Could coolant temp sensor be sending a bad signal?

 

I got my new multimeter. Tested the vafm like . It tested bad. I ordered a used one on ebay that the seller claimed was "good" in the description. It tested bad. I ordered a remanufactured one overnight from oreilly..........It tested bad. The original one actually tests better than the others. The truck still runs like crap with any of the 3 vafms plugged in and it runs perfectly with them unplugged. I guess I will send the two paper weights back and keep trying until I get one that tests good.

Original: E2-VS = 305 , E2-VC = .2 , E2-VB = 281
Ebay: E2-VS = 985 , E2-VC = .2 , E2-VB = 281
Oreilly E2-VS = 500 , E2-VC = .3 , E2-VB = 281



I was not able to pull codes by jumping pins T and E1 on diagnostic port. Took the cover off the ecu to inspect the circuit board. As you can see in the picture, the E1/E11 circuit was burnt in half. I got an ecu on ebay and now I can check for codes. the check engine light blinks continuously indicating no codes. At least that is fixed now.

 

Thank you for the update, hope you find a good AFM.

 

Well, the air flow meter test I was using above is for the 22re, which explains why all three units tested bad.

My original one tests good using this:

 

I wonder what burned it...