1fz-fe airflow meter tuning

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extremesitting

extremesitting

Joined
Jul 28, 2023
Threads
2
Messages
8
Location
West Texas
Hello everyone!

I've been struggling for well over a year to get my 93 80 series to run. I'll save the drawn out process I had to eventually arrive at the point I'm at now, but in short the following items ended up being problems and required attention:
  • TPS
  • IAC
  • VAF
  • EGR (eventually deleted)
  • O2 sensors
  • PAIR valve (eventually deleted)
  • Vacuum leaks under the intake plenum
  • Injector, TPS, and VAF plugs
  • Fuel pressure regulator
  • spark plugs
  • Fuel pump relay
  • Fuel pump
  • Fuel filter
Which leads me to the current state. I have a rebuilt VAF that "works". It tests fine and I'm able to get the truck to idle smoothly and rev high. However, to get there I had to dig in to the VAF quite a bit and compare it to a faulty OEM. I found that the clock spring that runs the flapper, and potentiometer was quite a bit more tight than it should probably be. That was leading to the engine failing to fully move the flapper. Not enough vacuum. I backed off the spring and got full range of motion with vacuum. Then I discovered that there was adjustment available in the armature itself which significantly helped the idle.

I finally have this thing running, but all this VAF tuning has me concerned that I could be following a procedure to set them up correctly. All my tuning has been by ear. I know there's a procedure to adjust/tune the VAF bypass though it didn't seem to do much, if anything, for me. Does anyone have any information on these meters beyond the generic install/testing process?

Ultimately I'd like to remove and replace the VAF with a MAF, but the conversion modules for that seem to be rare and information isn't that great for my year.

Thank you for your attention. I feel like I'm pretty far offroad with this project!
 
@Rifleman Thank you so much for your reply. I do have that spare VAF I could send off. Have you used that service before? If so, how much was the rebuild?
 
I have not had the need for their services yet, thank God, But i have read other threads here on mud that report that they do good work, As to their cost to rehab a VAF meter, their web site lists a cost of $365 dollars
 
Last edited:
extremesitting said:
@Rifleman Thank you so much for your reply. I do have that spare VAF I could send off. Have you used that service before? If so, how much was the rebuild?
Click to expand...

They did two for me earlier this year and they both work well. Expensive but our option in 93/94 VAF land are limited.
 
TheGrrrrr said:
They did two for me earlier this year and they both work well. Expensive but our option in 93/94 VAF land are limited.
Click to expand...
I've got my spare VAF packaged up to send off. In the meantime I have the frankensteined VAF in the truck and it's running ok. I'd need a wideband O2 sensor in the exhaust to get the tune better than it is right now and going that route would cost about as much as getting the spare rebuilt correctly. It idles really well, but it's not a happy camper before it's warm. FWIW the ECT checks out fine.

Did you have to tune the air bypass screw in the VAF after installing the rebuilt units? I'm hoping that's pretty close but it is designed for fine adjustment of AFM as needed.
 
extremesitting said:
I've got my spare VAF packaged up to send off. In the meantime I have the frankensteined VAF in the truck and it's running ok. I'd need a wideband O2 sensor in the exhaust to get the tune better than it is right now and going that route would cost about as much as getting the spare rebuilt correctly. It idles really well, but it's not a happy camper before it's warm. FWIW the ECT checks out fine.

Did you have to tune the air bypass screw in the VAF after installing the rebuilt units? I'm hoping that's pretty close but it is designed for fine adjustment of AFM as needed.
Click to expand...

I just installed it and rolled. Truck runs great. I wouldn't even know what screw to adjust.
 
If you have replaced all those parts with new OEM Toyota and it still won't run, I think you can only have one of two problems: the engine harness or the ECM. or maybe both.
 
i'm about to sendoff my AFM from my 94 to the Bavarian boys, is it really just to a UPS store in the bay area?

any tips for packing it so it doesnt get too beat up? thanks.
 
No experience with Bavrest but I've heard a few good reports over the years.

Since you have learned some of the tricks for adjusting these you can consider continuing on the diy path, which could include adding a wideband o2 / air-fuel ratio gauge and then working to get the tune to where you want it with the AFM on/in the truck. I've not done this on an 80 / odb1 toyota so you'll have to do your own research to ensure this is a viable option. On other vehicles I've successfully added wideband o2 with real-time air/fuel ratio gauge and then been able to tune the afm under operation until I got the fuel ratio, power and operating temps that I was aiming for. How the computer manages AFM input vs other signals like temps, factory o2 sensors and timing adjustments will need to be understood so that you can reliably understand the impact that your AFM tuning changes are having. I also found it beneficial to add cylinder head temp sensor / gauge so that I could monitor tuning impacts on operating temps that are less buffered than coolant. etc.

A benefit of the DIY approach is that it may help you have confidence in your setup with the ability to manage it long term. Many folks may prefer, and have more confidence in sending the unit to someone like bavrest and then having it operate within factory specifications. I'm not sure which camp I'd fall in with an odb1 80 and it would likely depend on how stock or modified the engine systems were beyond the afm.
 
Okay, I'm going to add a little something to this thread. I just watched an old U Tube video by THE CAR CARE NUT. For those Mud members who may not know who this guy is. He worked as a master Toyota tech at a Toyota dealership for 10 years before opening his own shop specializing in Toyota, and Lexus. The subject of the video i watched was on when, and how, or if you should even try to clean a Toyota MAF sensor.

He went over vain airflow meters, old style MAF sensors, and the newest styles of MAF sensors. In the video he said that the old style of MAF with the temp bulb and heated wire is cleanable with MAF spray cleaner. He went on to say that the newest style of MAF sensor has 2 heated wires along with some type of micro chip in it, and if you try to clean it you'll ruin the micro chip inside it thereby destroying the sensor.

He finished off the video by talking about the vain airflow meter used by Toyota in the 80's to the mid 90's like the one's used in our trucks. He said to NEVER TRY TO CLEAN the inside of this meter (the swinging door inside it is VERY FRAGILE and easily damaged) or to open it up and try to repair/adjust it yourself. His suggestion if it tested out as being bad per the tests listed in the factory service manual. That it was best to have it repaired/serviced by a company that knows what they are doing, and has the tools and experience to repair it correctly.
 
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