89T AFM failure - 7MGTE

bosco659

bosco659

Toyota nut
Oct 11, 2005
42
0
0
Canada
After driving on the same afm for over 20 years, all of a sudden I have gone through two afm's in about 3,000 miles. Bad luck or is there something that might be causing this frequent failure. Al wiring looks good and afm body is solidly mounted to the wheel well.

Any ideas?

Thanks
 
bosco659

bosco659

Toyota nut
Oct 11, 2005
42
0
0
Canada
No oil leaks down accordion hose.

Car ran well with original afm then suddenly failed throwing a code. Threw in a spare used one and car ran fine. Drove for about 3000 miles without issue and then one night coming up to a stop light the car stalled and the check engine light came on. Threw a code for he afm. Put in another one and car runs fine.

Agreed could have been a used one on its way out.

Wiring at the afm is in good condition. Tested continuity between afm plug and wiring upstream and no breaks or bad connections. I suppose there could be an issue further up in the wiring harness.

When the engine threw a code it would still idle ok but with light acceleration the engine would misfire and stall.

Will see how the most recent unit lasts. Thx for comments.
 
Last edited:
Mikael_7m

Mikael_7m

Built 7M
Apr 26, 2009
283
0
16
Australia
Hope someone can shine some light here for me.
I am having this exact issue now. Had been running with the same AFM sensor for several years and it fails recently. Installed one from a friends car and it ran good for a month or so and then threw a code 31 again. I just tested the wiring at the ecu connectors.

VC and E2 = 5V
THA and E2 = 5V
KS and body ground:
while ignition is on = 5V
Engine running = still 5V

Car will start and run at 10:1 and will rev but misfire. Barely wants to idle.
What else could be wrong, is it in fact the AFM that's gone bad again?

p.s my accordion hose is a little oily on the inside.
 
Nick M

Nick M

Black Rifles Matter
Sep 9, 2005
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Mikael_7m;1973292 said:
Engine running = still 5V
Click to expand...

What is 5V running? Both KS and THA, or just KS? If you have 5 volts on any car, as they all have 5V refrence, the resistor is unplugged or open. If it was short (electrically) it would show ground.

KS is a frequency measurement. Put your meter on Hz and see what it says at idle.
 
Mikael_7m

Mikael_7m

Built 7M
Apr 26, 2009
283
0
16
Australia
Nick M;1973345 said:
What is 5V running? Both KS and THA, or just KS? If you have 5 volts on any car, as they all have 5V refrence, the resistor is unplugged or open. If it was short (electrically) it would show ground.

KS is a frequency measurement. Put your meter on Hz and see what it says at idle.
Click to expand...

Sorry I was supposed to say that the Ks and body ground either running or not was still 5V.
The rest checked out with the TSRM with ignition and while running.

I'm not entirely confident at using a mulitmeter yet. Not sure if mine has Hz.
Mine looks like this one:
1284950296651_hz-cnmyalibaba-web2_3335.jpg
 
Nick M

Nick M

Black Rifles Matter
Sep 9, 2005
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If you have 5V at VC (voltage constant) at the meter and no Hz output, then the meter has a problem. You should check against E2 ground.
 
Mikael_7m

Mikael_7m

Built 7M
Apr 26, 2009
283
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Australia
Nick M;1973457 said:
If you have 5V at VC (voltage constant) at the meter and no Hz output, then the meter has a problem. You should check against E2 ground.
Click to expand...

Sorry i'm a little confused. I tested VC and E2 with the multimeter. I stuck the positive rod in the VC and the negative rod in E2. It was reading 5V with the ignition on.
Have I measured it incorrectly? Still learning how to use the meter. Could you explain more about the Hz?
 
Nick M

Nick M

Black Rifles Matter
Sep 9, 2005
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Hz is cycles per second. The cycle in this case is on/off of the signal. This is a function of the Karman Vortex meter. 5 volts on VC and E2 is correct. You do not use voltage to measure the AFM output. You use Hz, which I don't see on your Harbor Freight meter. There is a book spec from Toyota not in the repair manual. 30 Hz at idle.
 
Mikael_7m

Mikael_7m

Built 7M
Apr 26, 2009
283
0
16
Australia
Nick M;1973547 said:
Hz is cycles per second. The cycle in this case is on/off of the signal. This is a function of the Karman Vortex meter. 5 volts on VC and E2 is correct. You do not use voltage to measure the AFM output. You use Hz, which I don't see on your Harbor Freight meter. There is a book spec from Toyota not in the repair manual. 30 Hz at idle.
Click to expand...

Thanks for clearing that up. I might have to invest in a more advanced meter and learn how to use it properly. Thought i'd add that I installed another AFM this morning and car runs good again. Far out, why is my car chewing through these AFMs. They're getting harder and harder to find. Standalone time.
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
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Redacted per Title 18 USC Section 798
The trick to longevity with the Karman is to keep what it's breathing clean. That means no water or oil along with a good filter that isn't changed before it's due, which is something most people mistakenly do. My filters usually went well beyond 60K miles before reaching the pressure drop limit I set. Even though they looked god-awful filthy I knew they were filtering better than new as time went on.
 
7M4EVR

7M4EVR

New Member
Oct 8, 2012
695
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0
fah, fah away
JJ sorry for a possible dumb question, but how do you monitor this pressure drop? And thanks for sharing, i didnt know a filter that is essentially "broke-in" would filter any better than a brand new one.
 
7M4EVR

7M4EVR

New Member
Oct 8, 2012
695
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fah, fah away
Cool thanks...extremely basic stuff but new to me. I might have to pick me up one of those just so when people asks me what it is I can seem like I know what I'm doing lol.

This would be especially great for cars that the air filters are enclosed and a pain to get to to check to replace.
 
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