kcoughlan

I began having a stalling issue with this 95 4runner v6 about a month ago and now after replacing MAF, Fuel pump , fuel filter, air filter... cleaned EGR ,throttle body and air/fuel manifold, checked TPS(seems fine) , it will only start strong but putters out within a few seconds. Feels like it's running out of fuel or it's getting way too much air. Engine codes shows clear. Any thoughts on the possible causes of this ?

scope103

"Starts but putters out in a few seconds" is the classic sign of a VAF-COR issue. Fortunately, it is the easiest thing on your truck to diagnose (and costs a whole lot less than MAF, Fuel pump , fuel filter, air filter...)

Jumper FP to B+ in the diagnostic connector. This forces the fuel pump to run with only key-on. Does the 4runner now run? This means your VAF and COR together are not keeping the pump running when you let go of the key.

Don't drive around with the jumper in. If you get in an accident that breaks a fuel line, do you want the fuel pump to keep running while you're dangling from your seatbelt?

kcoughlan

Thank You for your post ....I tried as you instructed and sure enough it fired up and stayed running, although it was a high idle. (I think I have the cold idle screw out of adjustment )At one point today I started getting code 24 ,which indicated intake air temp sensor but that is in the MAF on this rig... Does this mean the MAF sensor I bought is bad? I'm researching VAF_COR now to figure out what that means and how I fix it. Thanks Again, I was getting close to thoughts of suicide and you're the first person to come up with a diagnostic that works......did I mention THANK YOU !

scope103

The intake air temp sensor is inside the VAF ... do I detect a pattern here? Diagnose the VAF:
http://web.archive.org/web/201003261...92volumeai.pdf
(You have a Vane (or Volume) Air Flow sensor. A Mass Air Flow sensor uses different technology. Not that it really matters here.)

Since (you say) you've already replaced the VAF, you must know this:




(of course, if you made the obvious mistake and tore up all the wiring inside your "new" VAF, THAT would explain your issues.)

kcoughlan

I never messed with this unit other than putting it in and taking it out .It was a reconditioned Oreilly auto part and I hope the next one I got will solve this issue. I also discovered my cold idle screw o-ring was old and worn flat...would that have given me a surging Idle ? Thanks again......

kcoughlan

Another discouraging day...installed "new" VAF and secured all appropriate hoses and connections and no go...Rig will start but immediately quits. I cannot hear the fuel pump turn on when I engage the key either. If I jump FP - B+ the pump goes on and the engine fires and stays running. I have cleared the codes by disconnecting the pos batt terminal and turning on the key and letting it sit, still get the same reaction.The codes are clear . I am looking at either the cluster pigtail that plugs into the VAF or the computer itself although I would think if it was that the rig would'nt have progressively gotten worse it would have just died a month and a half ago when the problem first started......?????I've been shopping ecu's online..is there any compatability with other model #'s? will an 89661-35890 work the same as a 89661-35870(which I have) ? or should I match it exactly.

scope103

Oh, man. With key-on (and no jumper) you should NOT hear the fuel pump. Only when you turn the key to STArt (and then you won't hear the pump over the noise of the starter). Once the engine starts sucking air, a switch in the VAF closes, it energizes a second coil in the COR, holding the COR closed to keep the pump running. THE ECU DOESN'T GET A VOTE IN THIS, so stop blaming the ECU!

Is it a bad VAF? How would anyone know? You TEST it. http://web.archive.org/web/201003261...92volumeai.pdf Use your multimeter FC-E1 to see if the circuit closes when you push the flap with your finger. You know that half of the COR is working (because key to STArt closes it), but you may need to check that the second winding is good too. Another multimeter job: http://web.archive.org/web/201003261...96circuito.pdf

What if both parts test good? Then it's the wiring between them (which includes that connector that you've been making and breaking so many times in the past few days.)

This isn't that many parts, or wires. Be systematic; your solution is nearer than you think.

kcoughlan

I found possible water stains on my circuit opening relay located just above the ECU with partially corroded connections....I have a leaky windshield which often allows water to wet the carpets up front. Could this be causing the signal to be hijacked ? I have inspected the pigtail going into the VAF and it all appears to be intact with no signs of wear or damage. I've been cautious with this connection and have not broken it,,yanked it or forced it .

scope103

Oooh. Water and electronics don't mix. Rain water on the COR keeps on following gravity to the ECU. Full of easily corroded electronic components ...

But you cannot tell the electrical condition of a relay (connector, etc.) solely by looking at it. That's why you invest $6 in a fancy digital instrument.

But if you really don't want to do it the easy way, there's one last shortcut. With key-on, push the VAF flap. You should be able to HEAR the COR close (and run the pump). If you don't hear it, you still don't know which part is to blame, but you've confirmed the area.

kcoughlan

hmmmm... I think I finally found my issue, off to the parts store.....if this isn't it I going to go insane....... Thanks again for bearing with me and directing me to find this problem....I'll be picking up a multi meter too, very handy tool

scope103

Okay; I take it back. There are SOME cases where you can tell the electrical condition just by looking. ;^) (Actually, the part may be "OK" electrically, but with that much rust it will surely fail soon.)

Let us know what you pay for the replacement. Toyota (from a dealer on internet) gets about $105. http://parts.lakelandtoyota.com/prod...erm=8591035010 RockAuto has a Denso now for $31.

And here's your fancy $6 digital instrument. http://www.harborfreight.com/7-funct...ter-90899.html

kcoughlan

Success ! Installed COR and cleared all codes(cost me $116.00 at Orielly auto, convenience buy) ,started ,runs great with a 700 rpm at Idle. Being a novice I learned many things during this process the biggest of which is too have a meter and the ability to read and diagnose the issue with it. I'm much more comfortable with this rig now that I have poured over it and cleaned and replaced many parts that sorely needed attention. I bought this with over 200,000 mi. and it was very well taken care of for all those miles so I'm confident it will perform much better now with the overdue TLC.....I guess I'd better get a new windshield soon, although I fashioned a plastic shroud around the COR to protect from any water just in case. Thanks again for your suggestions and patience....another 2nd Gen 4R still cruisin America......

scope103

Thanks for the report (and the price check).