Hi guys, forgive me if this has been covered previously a thousand times, ive searched the archives and can't find anything that answers my question directly, that may be because ive not searched properly! Any way ive got a 2000 A4 1.8 TQS totally standard, the other day on the motorway it all of a sudden accelerated like never before, felt really good. Since then though feels really flat and powerless, MPG's have gone up and fault code 16487 has popped up, anyone got a clue where to start looking, what the possible causes are etc?

Thanks

 

Sorry, make that MPG's have gone down!!!

 

That code definition is:

16487 = MAF short to positive

Check the wiring for your mass airflow sensor (inline on the intake piping to the throttle body). You may want to get some electrical contact cleaner and clean the contacts - that may help. If not, you're probably looking at a new MAF sensor.

 

Ok, i can check that out as im an electrical engineer, i suspect that the MAF has an internal short circuit then, i was kind of hoping a quick clean and it would be fine. I will check it out, thanks for your help man

 

Just a quick thought, anyone have any testing method for the MAF? resistance values etc.

 

I don't have them offhand, but I'll be working on my car today, so I'll get pin-to-pin measurements and post them here. My MAF has no problems and I have no codes, so I should be seeing accurate readings.

 

Well now im confused! I cleared the fault codes and drove around this morning for a while, checked the codes again to see if the same codes popped up and nothing! However the problem still exsists, i took a look at the MAF sensor anyway it was spotless, gave it clean and went for another test drive, the problem is still there, no power almost like there is no boost and i cant hear my turbo anymore, the fault code hasnt come back either! What now?

 

In order for it to throw a MIL on an OBDII car, the fault needs to happen 3 times under the same conditions. Keep driving, it will come back on.

Do you have a way to look at fuel trims and O2 sensor readings (scan tool or VAGcom)?

 

I do havea way of looking at readings but the software i have doesn't support all the functions as it isn't registered! I must say it felt much better coming to work this morning, but it is still down on power. What do you suggest by looking at the fuel trims & O2 sensor?

 

Looking at the fuel trims can tell you if your MAF may be giving you false readings. Looking at the 02 sensor readings is just a guideline to make sure the feedback system is working up to speed and to dually verify possible false MAF readings.

For example: If you MAF was giving false high readings, your ECU would bump up the fuel trims. The O2 sensor readings would then show a rich condition because it's dumping unnecessary amounts of fuel.

But the fact you had a code specifically for MAF short to positive is interesting. It makes me think you have a wiring issue (internally or externally), not necessarily just a sensor issue as I was implying. There's no standing water in your cowl around the ECU water box by chance, is there?

Resistance readings of a good MAF would be best. I don't have access to a wiring diagram right now, but I'll try and dig one up.