Here is a Ford bulletin on bad MAF's. Some of it may apply:

ISSUE:
This TSB article is a diagnostic procedure to address vehicles that exhibit lean driveability symptoms and may or may not have any Diagnostic Trouble Codes (DTCs) stored in memory.

ACTION:
Follow the diagnostic procedures described in the following Service Tip. The revised diagnostic procedure is a more accurate means of diagnosing the symptoms.

SERVICE TIP

MASS AIR FLOW (MAF) DISCUSSION
MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.

If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle.

NOTE: THE FOLLOWING PROCEDURE MAY ALSO BE USED TO DIAGNOSE VEHICLES THAT DO NOT HAVE FUEL SYSTEM/HO2S SENSOR DTCs.

Symptoms
Lack of Power
Spark Knock/Detonation
Buck/Jerk
Hesitation/Surge on Acceleration
Malfunction Indicator Lamp (MIL) Illuminated - DTCs P0171, P0172, P0174, P0175 may be stored in memory

OBDII DTCs
P0171, P0174 (Fuel system lean, Bank 1 or 2)
P0172, P0175 (Fuel system rich, Bank 1 or 2)
P1130, P1131, P1132, (HO2S11 lack of switching, Bank 1)
P1150, P1151, P1152, (HO2S21 lack of switching, Bank 2)


Look at the BARO PID. Refer to the Barometric Pressure Reference Chart in this article. At sea level, BARO should read about 159 Hz (29.91 in. Hg). As a reference, Denver, Colorado at 1524 meters (5000 ft.) altitude should be about 144 Hz (24.88 in. Hg.). Normal learned BARO variability is up to ±6 Hz (±2 in. Hg.). If BARO indicates a higher altitude than you are at (7 or more Hz lower than expected), you may have MAF contamination. If available, Service Bay Diagnostic System (SBDS) has a Manifold Absolute Pressure (MAP) sensor that can be used as a barometric pressure reference. Use "MAP/BARO" test under "Powertrain," "Testers and Meters." Ignore the hookup screen. Connect GP2 to the reference MAP on the following screen.

 

I have replaced 2 MAF sensors in 1 year (2 year old TT). I have an Upsolute chip. The first MAF sensor went bad 6 months after the chip was installed. The second was 1 year after. I think that the chip may make the acceptable range of MAF sensor operation more critical (narrower usable range) and is therefore indirectly related.

 

I am 6000ft above sea level. I corrected my mistake in my previous post. There is also an O2 pronlem that is causing a CEL.

 

What symptoms does the car exhibit when the MAF goes bad? In other words, How do you know it's bad?

 

What codes are you getting when you are deciding the MAF is bad? Are they just O2 sensor faults such as 1123 and 1125?

 

A sudden drop in power accompanied by PSM and ABS lights.

 

MANA I would like to see logs of your MAF. Being 6,000 feet up your turbos have to work extra hard to produce to same boost as a car at sea level. All of that extra air gets pulled past the MAF.

I assure you my previous suggestion will work.

 

Don't the turbos have to work extra hard to get the same amount of air [boost] to the engine as at sea level? Isn't the point that at 6000' there is less air? How would getting the same amount of air past the MAF be a problem???

Mike

 

ABS, PSM lights are the dead giveaway with no CEL. The CEL side will throw 1125, 1128 which are O2 errors normally associated with adaptation, fuel pressure etc. The odds of both left and right banks going out without failed turbos are less than none.

FWIW we see little failure on the pre 2000 cars since they are not drive by wire. Same does for Egas Audi and VWs.

 

I blew my MAF about 2 weeks after installing the EVO airbox.

 

mine went about two week later.



boris

 

Well I had a new MAF installed and made it home without an issue ....

 

Glad to hear you've at least made it that far...and whatd ya think of the 500hp Cayenne turbo?

 

Thanks!! I'll be ordering a CT later this week ...

 

Hey Bill, I live over in your area, how about a ride in that thing sometime? I've never been off the dealer lot in it, and its just so mysterious to me how it feels beyond 10% throttle. That'd be awesome And its a damn good thing we got a bolt in that brake pad hold-down pin, the inner pad was startin to rattle.