Hermosa

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Originally posted by lexiss_sc400
Oh yea how bad is it excatly to run with my MAF disconnected, I heard that my car would just be running lean. But would it mess up any part of my engine or cause the engine to fail.
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I just noticed that there is no signal from my Karman AFM anymore (93 SC400). I was wondering why my fuel mileage was so bad lately. I think when there is no signal from the MAF, the car follows some sort of default safe fuel curve based on RPMs and throttle percentage. The car runs fine but is as pig rich as a NA car could be. I am getting roughly 230 miles per tank right now.

Anyway I will double check the AFM again and then buy another too see if I can record a difference.

Hopefully I can report back on positive results.

Any comments on this hypothesis?

Current state is a fluctuation of 0.065 to 0.090 volts all the time whether at idle or WOT.
Compare this to a plain wire in the car with a fluctuation of 0.000-0.015 volts.

Hermosa

Okay did a check and found out the behavior.

Karman AFM was okay.

It appears that when the ECU thinks that the signal from the AFM is not making sense (piggy back ECU making it too lean) then it shuts down the AFM and uses a "safe" fuel map based on other parameters(rpms, throttle, etc). At that point you could actually remove the AFM and the car will drive the same.

The voltage from the AFM when it was being read was a periodic fluctuation between the current reading and around 5V which is maximum.

Lexiss_sc430

iTrader: (2)

Hey Hermosa,
You know the weird thing is that my car actually performs better when the MAF is disconnected; I launch way better and the car bones out off the line. My shifts are strong and the car actually leaps forward after the shifts, its like in-between shifts it gets a kick in the ***, its tight. The only think I have noticed that is a problem is that I run a bit rich and there is a bit of black carbon residue on my exhaust tips when I run this way, oh yea and my gas mileage suffers a bit but I'm cool with it. Lastly from what I remember when I went to the tracks I got a better time by .04 when I ran with my MAF off.
I dunno what can be going on but any info would help. i.e. if its bad or good

Tommy

Hermosa

Well my car ran 12mpg until I found out what happened. Fuel was spitting from the exhaust pipes. Mileage is now back to normal. Did your car work fine after you reset the ECU or did the check engine light stay on? If so then replace the sensor in the AFM. It is easier to replace than the entire AFM assembly.

Does anyone know the effective max temperature for the AFM?