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Discussion Starter #1
Hi

now really need help.

so 1992 manual turbo supra stopped boosting more than 0.3. I changed knock sensor. After that it started shut the engine in the trafficlights when warm.

After that i cleaned maf sensor.
Now i can start the engine easily. Iwill be running 1-2 second and shutdown. It will not respond any gas during that 2 seconds.
Could here be somekind of stock immobilizer or what this really could be?
I am out of ideas now. Thank you for help!
 

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if a intake hose ripped/cracked it would give your similar symptoms. the entire intake needs to be sealed bc the car has to draw all air through the air flow meter. a leak anywhere in the intake tract (all the plastic/rubber hoses) would cause the issues you are seeing.

can you elaborate on how you cleaned the air flow meter ? very easy to destroy the delicate electronics in there by spraying solvents in there.

have you pulled the diagnostic codes to see what faults the ecu is recording / storing ?
 

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Discussion Starter #3
Thank you.
haven’t check codes, because engine light Stay off. But probably could still read them.

I cleaned the maf with this maf cleaning spray from rcr and let it dry few hours. Did you think that I broke the air flow sensor?
 

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Why did you replace a knock sensor? And how did you "clean" the AFM... (Ps, you don't have a MAF), AFM sensors are extremely delicate and it could be possible you destroyed it.
 

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Discussion Starter #5
Why did you replace a knock sensor? And how did you "clean" the AFM... (Ps, you don't have a MAF), AFM sensors are extremely delicate and it could be possible you destroyed it.
Why did you replace a knock sensor? And how did you "clean" the AFM... (Ps, you don't have a MAF), AFM sensors are extremely delicate and it could be possible you destroyed it.


I replaced it because wiring was shit so i make new wiring and sensor.

I cleaned it with crc maf cleaning spray.
How do i know if i just destroy it.?
Makes sense because car wont start after AFM cleaning.
 

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I wrecked my first airflow meter years ago by cleaning it with spray. It was an expensive lesson to learn. You can wipe off any oil from the exterior but nothing goes in those holes. One time I left it unplugged and had a surprising start up. You can pick up an airflow meter on eBay with the following part number. 22204-42010 Watch out for people selling Lexis airflow meters. They have a slightly different part number.22204-42011 They may work, but I would go with the OEM part number.
 

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The TSRM troubleshooting guide that Captain posted will most likely help you find what is wrong.

My off the wall guess from similar symptoms a very long time ago with my first Supra? Make sure your AFM harness is plugged into the AFM. Sounds obvious, but start with the simple things first!
 

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Discussion Starter #9
I wrecked my first airflow meter years ago by cleaning it with spray. It was an expensive lesson to learn. You can wipe off any oil from the exterior but nothing goes in those holes. One time I left it unplugged and had a surprising start up. You can pick up an airflow meter on eBay with the following part number. 22204-42010 Watch out for people selling Lexis airflow meters. They have a slightly different part number.22204-42011 They may work, but I would go with the OEM part number.
Thank you.
I will test that troubleshooting and if not working i will order new one.
Well at least now i know that I have afm and not maf :)
 

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I wrecked my first airflow meter years ago by cleaning it with spray. It was an expensive lesson to learn. You can wipe off any oil from the exterior but nothing goes in those holes. One time I left it unplugged and had a surprising start up. You can pick up an airflow meter on eBay with the following part number. 22204-42010 Watch out for people selling Lexis airflow meters. They have a slightly different part number.22204-42011 They may work, but I would go with the OEM part number.
FYI, the KV sensor in the "Lexus" AFM's will work.
 

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Discussion Starter #12
Okay, now engine is running but still boosting just 0,3 bar. fault codes are 21 and 31. what exactly this 31 code is? is VAF same as AFM? or
 

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Okay, now engine is running but still boosting just 0,3 bar. fault codes are 21 and 31. what exactly this 31 code is? is VAF same as AFM? or
21 is your O2 sensor and 31 is the AFM signal.
For the O2 sensor, follow this: TSRM O2 Diag
As for the AFM code since you've tested the AFM and it seems to be reading right, it's time to trace the wire from the AFM connector to the ECU. You'll want to trace THA, KS, and E2 back to the ECU and measure the resistance from connector to connector. I high resistance would indicate problems in the wiring itself which can lead to throwing the code 31.

Hi I did this and ohmmeter says 3,23 so its okay, but this only meter that temperature signal is working? How I can test more my AFM so I really know if it measure air or not?
The temps listed are to show what the resistance should measure for that given range. If you're getting a reading of 3230 ohms I am going to guess/hope it's around 10ºC when you measure it. The actual airflow measurement is tricky and I know of no way to measure it with common tools. Best bet here is to measure the resistance from AFM connector to ECU connector to make sure the wiring is good.
 

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The 31 code means the Karman Vortex signal or air signal from the MAF is not making it to the ECU. Like Captain said, meter the 3 wires he mentioned from the MAF to the ECU. Also make sure there is 12 volts to pin 4 on the MAF and that pin 5 reads to ground. Just put the positive lead on 4 and negative on 5 and that will check them both.
 

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Discussion Starter #15
21 is your O2 sensor and 31 is the AFM signal.
For the O2 sensor, follow this: TSRM O2 Diag
As for the AFM code since you've tested the AFM and it seems to be reading right, it's time to trace the wire from the AFM connector to the ECU. You'll want to trace THA, KS, and E2 back to the ECU and measure the resistance from connector to connector. I high resistance would indicate problems in the wiring itself which can lead to throwing the code 31.



The temps listed are to show what the resistance should measure for that given range. If you're getting a reading of 3230 ohms I am going to guess/hope it's around 10ºC when you measure it. The actual airflow measurement is tricky and I know of no way to measure it with common tools. Best bet here is to measure the resistance from AFM connector to ECU connector to make sure the wiring is good.
thank you!
if I want figure out my wires from o2 2 heater wires should give me 12v and the one that goes to ecu will give me less than 5v right?
 

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The 31 code means the Karman Vortex signal or air signal from the MAF is not making it to the ECU. Like Captain said, meter the 3 wires he mentioned from the MAF to the ECU. Also make sure there is 12 volts to pin 4 on the MAF and that pin 5 reads to ground. Just put the positive lead on 4 and negative on 5 and that will check them both.
thank you!
so problem will probably be in those 3 wires.
 

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thank you!
if I want figure out my wires from o2 2 heater wires should give me 12v and the one that goes to ecu will give me less than 5v right?
Heater will be measured by resistance and the signal to the ECU is a bit more complicated but covered in the flowchart that I linked to above.
 
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