KE-Jetronic Air Flow Meter Potentiometers

Hello FChat,

I am banging my head against a wall regarding the Air Flow Meter Potentiometers in my US F113A040 engined 1990 Testarossa KE-Jetronic. I've always had a funky acceleration issue when AFR tuned "properly" so I've been compensating by richening the mixtures with medium success. I'm ready to fix it right, so after testing everything else, I'm down to these potentiometers...

I have tested both pots at the air flow meter terminals, and both have a dead spot somewhere between 3700 Ohms and 4200 Ohms. All the information I can find regarding testing these pots says there should be a smooth curve of resistance from 800 ohms to 5300 ohms, but BOTH of mine have this dead spot in the same place. Ok... no big deal... replace them both I thought. I ordered two new ones from ebay, but they're not the same spec as the originals, different resistance between 1+3 terminals, and different range of resistance through the sensor plate travel on terminals 1+2... Ok... wrong parts... find the right parts... easier said than done.. So I started thinking, maybe my original parts are Ferrari specific, and not faulty? Which then begged the question, "Should there be this dead spot in the resistance travel?" Can anyone confirm the test results should be a smooth resistance curve through the entire range of motion of the air flow meter travel?

I mean, what are the chances BOTH of my pots have a dead spot in exactly the same place? If the dead spots were in a lower range (like idle or cruise) I could understand, but this high in the meter's deflection, seems unlikely...

Here's a pic of the devices, I would expect some visual indication of the faults, but these look good!
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Many Thanks! I will absolutely test it this way.

 

Thanks for the proper test procedure... I performed it this morning and the voltage test revealed a similar result to the resistance test. I now believe I just need to find two replacement KE-Jet Air Flow Meter Potentiometers spec'd for this car. the part number on the housings is 3437224031, but I can only find 3437224035 or generic version(no number) from suppliers. Has anyone had luck locating any of these devices? I have only tried the cheap generic ones thus far, so I don't know if the 3437224035 fits the bill, can anyone confirm or deny?

It seems there is a specific range of resistance for these cars, as the generic replacements I tried were a different range...even when adjusting the small trim pot on the new devices, I couldn't get to the range the WSM specifies. My original pots certainly are in the proper range, just the gap at ~4000 ohm, which most likely explains my poor performance through acceleration and certain cruising rpms.
thanks

 

Thanks (I have searched...) , but that search only reveals the same "USED" ones your ebay link points to. Likely removed from a car with similar issues, because why else would they separate this device from a KE-Jet assembly?

I have emailed both Ricambi and AWItalian (neither has these particular parts), and searched endlessly, for days now...

So, has anyone had luck or experience with the 3437224035 version of this device? Or has no one needed these?

Steve, I very much appreciate your willingness to help and reply. But I do challenge anyone to find a pair of BOSCH 3437224031 Air Flow Meter Potentiometers, new, or compatible.

Thanks to all!
-john

 

I haven't tried an <actual> -035, only the cheap generic (no numbers) from ebay which were not the proper spec, not realizing there are variants...
I did clean the carbon tracks with electrical cleaner (no change), then with super-fine grit metal polish (came quite clean, although no change...)
If you look at the pic I posted, the tracks look pristine, so I was baffled to have the breaks in the pot travel...in the approx same places no less...
Even my 10x loupe can't see any evidence of damage or wear. Very weird and unlikely, but the tests don't lie...thus I must keep trying.

Given the hopeful post, I shall get a couple -035 units, bench test, and report back.
Thanks for your input!

 

Well, results are in... The KE_Jet Air Flow Meter parts advertised as 3437224035 do not match the original 3437224031 specs... at least on the bench.
I will try the parts in-situ with the test outlined by Steve M., and report results. If the voltage ranges are anywhere near the correct numbers, I'm probably gonna try to take for a drive with them...Anyone wanna talk me out of it with reasonable concerns?
This is a bummer for future repair outlooks, as I cannot find replacements at ANY ke-jet gurus for these potentiometer devices.
I am so surprised no one has had to deal with these in a repair...
thanks to all for input

 

The resistances measure as follows: (all values are approximate)

original device (3437224031) pins 1+3 : 450 ohms
replacement device(3437224035) 1+3: 1600 ohms

original device (3437224031) pins 1+2 : 850 ohms through 5400 ohms (with a gap at about 4000 ohms, like a scratchy volume knob on old radio)
replacement device (3437224035) 1+2 : 1900 ohms through 3000 ohms (smooth the whole way)

I conjecture that these results will mis-align the enrichment signal, thus I probably shouldn't test drive...any opinions??

To the last post-er: thanks for the links, but those are used devices with visible wear on the potentiometer tracks... most likely swapped out for similar issues, which is non-linear (scratchy) resistance tracking over the swing of the air flow meter plate.

 

Indeed... I will do the voltage test without running the engine.
I like the way you think!
thanks