What are others doing when their VAF’s go bad? ‘94 FZJ80 (1 Viewer)

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Sporadic rough idle at low rpm's. Will be idling nicely at an intersection or red light and then slowly begin not breathing well. Will get to a point where it almost dies. I've gotten into the habit of sliding into neutral and giving it a bit of gas to keep the idle a bit higher. I've changed my O2's, my spark plugs, my distributer and wires. Replaced the fuel filter and fuel pressure regulator. Troubleshot the EGR and fuel pump relay.
I cleaned the Mass Airflow Meter, which wasn't very dirty, and it ran perfect for 3 days with no CEL. I finally took it to the local Toyota dealership and they pointed at the mass air flow per the readings off of the multimeter master computer. I try to do as much as I can myself on my land cruiser. I've owned it for over 20 yrs and currently sitting at around 340,000 mi.
Sounds like it could also be a vacuum leak.
You said you redid PCV and grommet?

Vacuum hose is cheap as chips. Change all the vac hoses
Also change oil filter cap o-ring
 
When I bought my LC, I had really high cold startup RPM, then intermittent low idle and stalling once warm.

In my case, with ~254k miles, the O2 sensors were bad, the EGR modulator had failed at some point and allowed carbon into the intake manifold passages, my IAC valve port was full of carbon, bad EGR solenoid, and it had various vacuum leaks even though most of the hoses looked good.

With only 145k miles, maybe you don't have most of those problems. But it's still an old rig, and the rubber has seen a lot of heat cycle, so if I were you I'd replace all the vacuum hoses. Since you have to pull the upper intake to reach several of them, you'll be able to inspect it, check that the passages are clear, and test the solenoids under there.
 
Have to agree I'd exhaust every other possible avenue first. Idle Control Sensor? Align the throttle cable and throttle position sensor?
 
After rereading, it's probably not the VAF. I agree with you guys, I think there needs to be more troubleshooting. I wonder if the techs at Toyota are full of it when they claimed the VAF was indeed bad.
 
Have to agree I'd exhaust every other possible avenue first. Idle Control Sensor? Align the throttle cable and throttle position sensor?
My challenge is I feel I have looked at or changed out a majority of what would cause the issues I'm having. Why can't it be the VAF? Does it have a lifetime guarantee? I understand it more than likely shouldn't fail and a long list of contributors exist. But from the 6-12 months of reading, research, and wrenching I've done and if it looks, acts, and sounds like a duck, why can't it be the VAF? When I was in high school I drove a truck my Grampa had owned. A 1979 Mazda Rotary pickup that my cousin rolled. One day the engine stopped on me and I couldn't get it to turnover. My brother pointed out it had an engine fuse and to check it. Changed out the engine fuse and ran perfectly. What a great day that was.
 
I wonder if the techs at Toyota are full of it when they claimed the VAF was indeed bad.
From my experience, most Toy techs no longer have any idea what they’re doing with a vehicle that’s >15 years old. Occasionally they’ll have an old timer on staff who knows, but it’s rare.
 
My challenge is I feel I have looked at or changed out a majority of what would cause the issues I'm having. Why can't it be the VAF? Does it have a lifetime guarantee? I understand it more than likely shouldn't fail and a long list of contributors exist. But from the 6-12 months of reading, research, and wrenching I've done and if it looks, acts, and sounds like a duck, why can't it be the VAF? When I was in high school I drove a truck my Grampa had owned. A 1979 Mazda Rotary pickup that my cousin rolled. One day the engine stopped on me and I couldn't get it to turnover. My brother pointed out it had an engine fuse and to check it. Changed out the engine fuse and ran perfectly. What a great day that was.
Again, over the course of this troubleshooting journey, have you verified it yourself?
 
From my experience, most Toy techs no longer have any idea what they’re doing with a vehicle that’s >15 years old. Occasionally they’ll have an old timer on staff who knows, but it’s rare.
I agree. Once my VAF is returned from NAPA and its trip around the US, I'll be able to better troubleshoot some of the above suggestions I may have overlooked. My throttle cable isn't in the best shape but I don't believe it would cause the issues I'm having. You never do know. I need to find new friends. None of my friends know how to do squat. Working on an issue alone can get old.
 
So you actually have your VAF to Napa. Hope you took 5min to validate what Toyota told you before giving it to them.

How much are they charging you?
 
Borrow someone's working VAF from another 93-94. That will tell you if your VAF is indeed the problem. Otherwise, double check your throttle cable adjustment according to the FSM.
 
I not trying be disrespectful and not a 5-banana expert. After going down the same road, just basing my advice on the fact that finding a working replacement VAF is a wildcard at best so it's the last thing I'd focus on after trying ALL else. I hope you get squared away. :)
 
My challenge is I feel I have looked at or changed out a majority of what would cause the issues I'm having. Why can't it be the VAF? Does it have a lifetime guarantee? I understand it more than likely shouldn't fail and a long list of contributors exist. But from the 6-12 months of reading, research, and wrenching I've done and if it looks, acts, and sounds like a duck, why can't it be the VAF? When I was in high school I drove a truck my Grampa had owned. A 1979 Mazda Rotary pickup that my cousin rolled. One day the engine stopped on me and I couldn't get it to turnover. My brother pointed out it had an engine fuse and to check it. Changed out the engine fuse and ran perfectly. What a great day that was.

No- one is saying it's absolutely not the VAF.
just suggesting other possible contributors that may solve your problem for less cost

Example, eeplacing vacuum lines is maybe $20-50 for hoses, and a few hours work.

Vs $100's for VAF repair
 
No- one is saying it's absolutely not the VAF.
just suggesting other possible contributors that may solve your problem for less cost

Example, eeplacing vacuum lines is maybe $20-50 for hoses, and a few hours work.

Vs $100's for VAF repair
Sounds good... the vacuum lines were 1st on my list and replaced all a while back.
I got the VAF back from NAPA yesterday. Quick recap... NAPA has VAF rebuild on the website - https://www.napaonline.com/en/p/NECXTP420097
7-10 days they send off for rebuild. 40 days later nothing done due to local store not filling out correct paperwork. I may try another Napa location as they wanted to send off to a local place here in TX. Will try to find out if it's a 3rd party. So I've put the VAF back in and happy to drive the rig again. Same issues so will look at troubleshooting a few other areas this evening and weekend. Will research and look at checking fuel injectors and also testing the VAF myself with multimeter as suggested.
 
Sounds good... the vacuum lines were 1st on my list and replaced all a while back.
I got the VAF back from NAPA yesterday. Quick recap... NAPA has VAF rebuild on the website - https://www.napaonline.com/en/p/NECXTP420097
7-10 days they send off for rebuild. 40 days later nothing done due to local store not filling out correct paperwork. I may try another Napa location as they wanted to send off to a local place here in TX. Will try to find out if it's a 3rd party. So I've put the VAF back in and happy to drive the rig again. Same issues so will look at troubleshooting a few other areas this evening and weekend. Will research and look at checking fuel injectors and also testing the VAF myself with multimeter as suggested.
just curious if you had any updates on a solve or discovered it was a different part a year later...i might be on the VAF repair journey myself:nailbiting:
 
I'm wondering about updates to this also. I have 294K on the clock and sporadic rough idling, but always idles at 650 rpms. Ran the Toyocom and got codes 24 and 31. New vacuum hoses, air intake tube, PCV and grommet, and throttle cable installed. Could it be the cable and/or connector that connects to the VAF that's going?
 
I'm wondering about updates to this also. I have 294K on the clock and sporadic rough idling, but always idles at 650 rpms. Ran the Toyocom and got codes 24 and 31. New vacuum hoses, air intake tube, PCV and grommet, and throttle cable installed. Could it be the cable and/or connector that connects to the VAF that's going?
Try cleaning the IAC and iac passage.
 
Bench tested mine and it wasn't within spec (previously rebuilt by Bavarian Restoration with good results over a couple of years). Going to do a VAF to MAF conversion, but in the meantime just went to the parts yard and pulled the VAF out of an old ('90) Toyota sedan and put the circuit board from that VAF into the 80's VAF (the part number is stamped on the board and is the same as that for the 80). Made a few adjustments to the spring as well. Works fine and should get me through until the conversion.
 
Bench tested mine and it wasn't within spec (previously rebuilt by Bavarian Restoration with good results over a couple of years). Going to do a VAF to MAF conversion, but in the meantime just went to the parts yard and pulled the VAF out of an old ('90) Toyota sedan and put the circuit board from that VAF into the 80's VAF (the part number is stamped on the board and is the same as that for the 80). Made a few adjustments to the spring as well. Works fine and should get me through until the conversion.

Sounds like it could also be a vacuum leak.
You said you redid PCV and grommet?

Vacuum hose is cheap as chips. Change all the vac hoses
Also change oil filter cap o-ring
Mudgudgeon, you were correct. It ended up being a vacuum leak from the valve cover vent hose. I don't remember if it was the PCV valve, grommet, hose, or exactly what I did but it resolved the issue after a year of messing with it. I was reading my previous post and was sitting at 341,000 mi. I just got back from North Dakota over Christmas and good to go at 352,000 mi. I'm not a good poster but will have to share a fuel pump story from my trip at the right time.
 
Ordered two VAFs from ebay for my '94. One of them is chinese new part and the other is supposed to be (and seems to be) remanufactured OEM. Next to each other they are obviously different. Each was $99. Not sure the best way to test them off the truck, but my plan is to use one of them while the original factory one currently on the truck gets sent out for a rebuild or whatever. Thought folks might want to see what the two primary ebay options look like. Some photos:


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It's basically some potentiometers that are adjusted by the barn door.

I have a pdf somewhere of a troubleshooting guide for a bosch VAF on a Digifant2 volkswagen cabriolet and similar. It gave an idea of what the resistance should be between different positions on the connector through some positions. These would be different for each application.

Regarding "use a bmw one" there may well be a bmw VAF that will bolt on but you can be sure it will behave differently. There have been a lot of guys who turbocharged old 1.8L volkswagens who 'fixed' their lean running condition by swapping on a VAF from a BMW with a somewhat larger engine, which caused those cars to run rich instead. Some people's children, right?

But another concern with an aftermarket part would be whether the spring resistance on the barn door is - whether it moves the same for the same air as the original.

Years ago, my stumbling and low idle issues were gone after i replaced ALL of the vacuum lines, cleaned the IAC valve and its passage, and put band clamps on the air duct because the duct walls had been squished thin by the original factory wire loop type clamps. Of course, i did verify that there are no cracks in the duct.
 

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