Have been having a rash of strange MAF lately. All were over 10 years old. ECU/Consult showed no codes.They read correctly at idle [1.2 volts] but produce errors [higher voltage than is normal] as the flow increases.

One interesting unit [swapped on my Q] produced 4.55 volts at 5,100 rpm [vs maybe 4.15 volts normal]. The results were the injector time went from 10.3msec to 12.3msec [roughly 20-23% more fuel] and the ignition advance dropped by 2-3 degrees. The engine lost power and felt sluggish from extreme richness.

Perfect for a 50 shot of Nitrous but not very nice for a standard Q.

Research is underway as to the cause, as this seem the exact opposite of what used to happen with bad MAF......the voltage would be too low reading low air flow.......leaning the engine excessively.

My last MAF failure (1.5 years ago) produced excessively rich running as well.

So rich I was trailing soot.

Fred...

But that was at idle and low rpms...........these appear fine until WOT and 4-6,000 rpm..............some component changes making the temperature appear to drop [which makes the thin fim thermistor think more air is flowing].

If the heater were to generate less heat the system should respond across the air flow range equally.

Microscopic analysis and hopefully Bosch willl answer me?

Interesting. My Q has always had an issue with sooty exhaust (deposited on the top of the rear bumper and backside of the touring wing) as well as poor fuel economy (best of 16 mpg).

Given that I have access to the Master Techs here at S. of I., what should I have them test?

i would think they should hook up the consult and take it for a drive. consult will show maf voltage. maybe i should test mine, i don't get soot, but according to the wideband on the dyno my a/f dropped below 11:1 at 4200 and dropped off the chart at 5800. i attribute this to bad KS, but i can check the MAF easy enough, and it's free.

AZhitman wrote:Interesting. My Q has always had an issue with sooty exhaust (deposited on the top of the rear bumper and backside of the touring wing)

Thats how my AMF problem started, except it got worse real quick.

If you have soot deposited I would think a new MAF a good idea.

Fred..

Q45tech wrote:But that was at idle and low rpms...........these appear fine until WOT and 4-6,000 rpm..............some component changes making the temperature appear to drop [which makes the thin fim thermistor think more air is flowing].

If the heater were to generate less heat the system should respond across the air flow range equally.

Microscopic analysis and hopefully Bosch willl answer me?

Mine got so bad that by the end, I had to give it WOT just to maintain hiway speeds (or less).

Fred...

Well I spray cleaned the {bad MAF} with brake cleaner {{ screen up on a white paper towel to look at residue coloration [fully evaporates]}} and installed on a spare air box top [so I could swap easily]...............the {bad unit} seems good again or at least it is providing a more normal voltage compared to mine [and others tested]. Sample still too small to say for sure what is correct!!!!!!

http://www.seanhylandmotorsport.com/maf ... po...d=109

$300-$360 for the above device to modify the MAF output voltage in 400 rpm steps

Still higher at WOT [6,700 rpm] 4.41 vs 4.35 making the injection time 0.3 millisecs longer.........3,4,5% [???] more fuel but no loss of ignition advance.

There must be a cliff in programing above which it [some number] says TOO MUCH.I seem to remember 4.44 volts a few years ago [when it was very cold outside]. WE have seen 4.55 volts is tooooooo much.

A 32F day in Miami might be 6% denser air than my ATL 70F readings.......that would only add maybe 0.02-0.03 volts

Remember the equation to translate MAF voltage into air flow has a 2.5 power exponent..........so small changes at the 4.0 volt ranges are big changes in air flow.Without an exhaust gas temperature probe or a wide band O2 sensor.....or a dyno hard to tell what is the ideal.Each 0.01 millisecond is 1.2% at 10 millisecs [correcting for pintle rise time]. But luckily there is little difference in 10.5>11.5 AF as far as power production is concerned.

Maybe we'll get a 32F day soon [yuck] to correlate the change.

I drove home [10 miles but 35 minutes in traffic] with the {cleaned bad MAF} installed seemed ok, so far, but mine is sitting in the back seat with all the tools it needs to change it.

The seem to be good MAF, dirty MAF or inaccurate MAF, and BAD MAF.

Guess what the MAF started acting funky again after being good for 2 days...........back to my old 13 year old one on the side of the road.

maf, part of the nissan soul. one more thing to give the car character. mafs are so funny sometimes. i have a bunch of spares that are skewed one way or the other but still drivable. how do you monitor yours all the time? consult? generic scan tool? fancy gauge in the car?

Use a Consult so that I can store 50 readings [of all sensor data] per second of acceleration.Still looking for an inexpensive 0-5 volt small digital panel meter with peak store.

I must have 200 feet of chart paper with each sample being 6"......400 sample runs of all data on my car using the exact same location and zero to 80 mph runs broken down in 3 second increments.........in various ambient temperatures.

wow, has anyone ever called you a diagnosis nazi before?

j/k

That's my hobby, to acquire every diagnostic tool and insite available. Why else do you think I charge double the dealer rate to look at a car.............as here, mostly I give my time away.

man you are hardcore. do you have any factory training or what? what is your background?

Electronic Engineering BSEE, MS Physics, MBA. I am not a technican, nor do I work on cars for money. "tech" stands for technical not technican. [I actually worked with vacuum tubes in the mid 60's] before transistors were common.Owning a Q for almost 14 years helps plus I have access to T3 where the OLD ONES live!

Factory training is kindergarden, most of the best have 2 year trade school ASAE degree at minimum.