Suspected MAF failure please advise on graph

[chard]

Hi everyone,
I am having power loss problems and suspect my 3 month old genuine Bosch MAF sensor is failing.
I took a plot of it here in this graph. It appears to be giving much too low actual versus requested and also seems to default at just under 500 in a few places.
From this graph can anyone please advise if they think the sensor is failing as it seems hard to believe this is happening since it is only 3 months old.
Thanks.

 

[GTDI4]

Have you checked the map sensor on the intercooler pipe?

 

[chard]

There isn't a MAF sensor on the inter-cooler pipe. The MAF sensor is after the airbox and measures the mass airflow and it is this measurement that I have logged in vagcom and put in the graph. The graph shows that requested is not being met and sometimes it defaults to just under 500.
Is the graph visible in the thread as for some reason I just get an icon showing?
Looking at the graph it is strongly pointing towards a failing MAF sensor but I have only done around 1000 miles and had this sensor installed for 3 months, so I am surprised it has failed so early. I was hoping someone could review the graph and offer a second opinion.
The sensor in the inter-cooler pipe is the intake boost sensor that measures turbo boost. I don't have a problem with the pressure as far as I know.
Thanks for the reply.

 

[stennyboy]

What air filter you running?

How is the car running? What are the symptoms?

 

[FlyTDI Guy]

Keep in mind that MAF will follow boost so you could be having boost issues which the MAF readings are reflecting. Have you logged boost or do you have a boost gauge? Low readings could be due to intake restrictions like clogging, snow screen, dirty air filter, etc. Not sure what your operating conditions were when you logged but when checking your MAF, you should follow the instructions on Ross-Tech. See details here... http://www.ross-tech.com/vag-com/cars/tdi.html

If your MAF readings were dropping out, the default value is 550. A bad MAF will usually flat-line at that value regardless of specified. That could be constant or just intermittent as well. I'm not seeing that. What I am seeing is a lump after specified drops indicating boost is not dropping crisply. Try re-logging following the Ross-Tech instructions and see what you get.

 

[GTDI4]

There isn't a MAF sensor on the inter-cooler pipe. The MAF sensor is after the airbox and measures the mass airflow and it is this measurement that I have logged in vagcom and put in the graph. The graph shows that requested is not being met and sometimes it defaults to just under 500.
Is the graph visible in the thread as for some reason I just get an icon showing?
Looking at the graph it is strongly pointing towards a failing MAF sensor but I have only done around 1000 miles and had this sensor installed for 3 months, so I am surprised it has failed so early. I was hoping someone could review the graph and offer a second opinion.
The sensor in the inter-cooler pipe is the intake boost sensor that measures turbo boost. I don't have a problem with the pressure as far as I know.
Thanks for the reply.[/QUOTE
ID parts sells it as:2.5 Bar MAP Sensor (ALH)
[a4_25bar_map] In the Bentley Manual it is listed as Intake Air Temperature (IAT) Sensor (G72)> What ever the name In my case as you I was having the same problem. In my case I replaced the (what ever you want to call it sensor). It solve the problem. This was after testing the MAF and N75 valve.[/I

 

[whitedog]

The MAP sensor and the IAT sensor are two sensors in one.

OP, log the MAF as ROSS TECH outlines and post up the graph. What you have posted is just two and three second bursts. You need a hard pull.

 

[greengeeker]

As others have suggested - you need a better log of everything that is going on. Do a long sustained pull in 3rd (4th preferred) gear logging groups 1,3,11 from 1700 rpm to redline. This will give us the best indicator of what is going on with your car.

 

[chard]

Thanks for replies.

A bit more detail on my symptoms.

Mid December 2014 driving along, decide to give car full power in 3rd to clear things out a bit, get to around 4K rpm and then power suddenly drops back. From this time and for the next couple of days, power delivery is weeker just like a failed MAF.

I didn't take any plots with VCDS to verify, I just changed the MAF for a new one and all has been well until a couple of days ago.

So driving again recently I did the same thing in 3rd gear, got to around 4K rpm and power then feels a bit like before and drops away a bit. So I start to look at things and took the plot as per graph.

I guess it may not be the MAF and could be coincidence that when I changed it, the condition (whatever the problem really is) rectified itself reappearing again recently.

Today the car feels almost OK and I haven't yet had time to plot the recommended data but I will do this soon and post back once done.

Unfortunately my commute has changed to a 5 mile round trip, so the car doesn't even warm up properly, unless I take a detour. I don't like running the car like this but that's how it is for now. I wouldn't be surprised if the intake/EGR valve or VNT is getting clogged. I do take it out at weekends and give it a good blast.

I cleaned all the intake and turbo VNT at 65K miles. A few years ago now, and the turbo was free moving back then. The inlet was fairly cruddy but not as bad as some pictures I've seen. The EGR now looks like it is pretty chocked up, so I will take it off and peek inside the inlet manifold at the weekend. I don't think the problem I am having is down to clogging though, as I don't think it wouldn't rectify itself like this.

The other thing I have noticed over the last couple of years is that the engine is not as smooth when idling. The gear shift, sun blinds and sunroof vibrate a little whereas before they didn't. I'm probably due for injector servicing now at 122K miles. I'll check the balance in VCDS at the weekend.