Could it be a MAF Sensor

So I've had my 996 for a few weeks now and I initially reported getting a CEL. I took it to brooklands kent and Barry said it came up as an 'idle stop' which meant the RPM dropped below a certain level for a bit (I think I remembered that right anyway). It was then fine for a few days until I put another 200 miles on it then when I was running to the shops the light came on again. I've also noticed it's now started idling around 1k warm where it was 800 before and I can also smell some unburnt fuel from time to time. I'm thinking the MAF sensor isn't giving the ECU the correct data hence the unburnt fuel and high revving. I'm far from an expert though so I was wondering if this sounds right? I'd be keen to change it myself since it looks fairly easy have many people done this is it really as easy as unplugging and unscrewing the old one and replacing it? Thanks again !

Certainly worth a punt. Not expensive and very easy to do if you have security Torx bits. (If I remember correctly).

Cheers! They're not as cheap as I thought actually ~£170 but I might still have a go. I'll probably get a fault detector plug in for the OBDII. Only thing that concerns me is surely it would just say MAF is broken on the fault code if that was the case?

Hi Get a code reader. If you have a fault code it may point to a component or it may not. There is a lot of expertise on the forum to help you diagnose any issues. You will be able to read the MAF flow rate and voltage as well as things like fuel trims which can help diagnose air leaks and such. Just changing components is a bit hit and miss. Having said that if cost is not an issue and you enjoy tinkering then why not. All the best Berni

Thanks Berni. That sounds like a sensible first step. I got myself a cheapish one from Amazon let's see if it works and shows anything useful

I thought you had put this car through a PPI? Surprising then to hear of CEL and now MAF sensor so soon after collecting it? A PPI should have included a download of the DME and assessment/clearance of any fault codes that were generated in its time. Perhaps you should take it back to the guys who did the PPI and have them sort it all out. It is hard to imagine these faults happened spontaneously so soon after collecting the car. What else is lurking to eat into the bank account?

Hi Cheshire, Yes I had Sid from Porsche Torque do it and he didn't flag anything of this nature. That's a good idea I can give him a call

Just hand the problem back to the guy who did the PPI. I doubt this has developed so soon after you acquired the car. It is quite possible the car has been faulty for some time. These cars throw up fault codes which is why a PPI must include a full download of the ECU/DME data using PIWIS (not some cheap generic eBay code reader). PIWIS is the official Porsche fault code reader and has far more functionality than some cheap reader off eBay (which can still be useful in a limited sense). The PPI should check for logged fault codes and clear them. Sometimes the fault code cannot be cleared - when the affected part causing it has failed and needs to be replaced. This is a safety feature and prevents a mechanic clearing codes when a part needs replacing. That MAF sensor price is a Bosch price at £170. The official Porsche part is over £800. https://www.design911.co.uk/fu/pt25...7-05/996-TURBO-2000-05/Air-Mass-Flow-Sensors/ So you need to be sure it is the MAF sensor before replacing it. Trying this and that can become very expensive on a Turbo. They can eat money in your bank account for breakfast. It seems you need to get to the bottom of the CEL and idling issue. Was any of this highlighted in the PPI?

Have you tried just cleaning it? I did mine over the weekend as I had high fuel consumption and fuel smell on start up. Just remove sensor spray a ***** load of cleaner onto the exposed circuitry and in all the nooks etc. Let it air dry and reassemble. I've driven the car 30km since and there is a difference in both litres /100 (MPG) and no fuel smell anymore. Just be careful not to touch the resistor looking things. Jim.

I'd start by removing and cleaning the MAF sensor and also the throttle body (if you're in the area). You'll need a couple of cans of the appropriate cleaner. But ideally you'll get a code reader (or have the codes read) to see what's up before you start replacing parts. Some garages are only too happy to replace random parts at your cost instead of diagnosing the actual issue first.

Some inexpensive options for you to consider there. Good luck.

Thanks again. The PPI didn't flag any fault codes and this was tested. Porsche Torque is in Uxbridge a long way from me in south london so if it is something as simple as cleaning/replacing the sensor I'm happy to just do it myself. Do you guys have any tips on what cleaner to use? I've also read that you can ruin the sensor if you're not careful is it particularly delicate?

Can't help on this one. But I have heard it is pretty sensitive and it may be perfectly OK before attempting to clean it which renders it non-functional. If you are not sure, then consider taking it to an indy near you to have it tested and cleaned if required. That SE quadrant of England is liberally peppered with OPC's and indy specialists.

You've done well, I had mine for 8 years before I had the eml come on! A couple of years ago the engine management light came on and when I checked there was a code for idle fuel trim. P0175. I reset it and car was OK for about a year but then it happened again and this time had codes for both banks p0172 and p0175. I checked everything and could find nothing wrong, the maf voltage was in spec although at the high end! In the end I decided to replace the maf and that sorted it! Fuel trims back to the middle The car was smoother to drive although it has since gone a bit jerkier! I didn't notice any difference in idle So to sum up when my car had an over reading maf I got codes for idle range fuel trims and the car had become slightly jerky to drive over a couple of years. Idle was not affected. The previous maf had only done 25k miles but that was over a long time! I was still surprised it was faulty. I paid £170 from bosch dealer and it looked identical to the one I took out. Ipa is the stuff to use to clean maf, I tried cleaning mine and it didn't really help. Ps very rare to get code for maf, a bad maf usually gives codes for fuel trims or you get the ABS and PSM warning

How old is this car ? sorry if you said and i missed it ... early cars have an idle stabiliser valve on the side of the throttle body .. if applicable to your car then thats the first place to start . What fault code number did the garage get ? Maf sensors will never throw a fault code if out of spec .. only if open circuit . Maf is possible .. i'm not sure atm but its on the list . Best check .. a tester on the car , ignition on but engine not running .. maf voltage should be 1.0 volt .. there is a plus minus of 0.9-1.1 but imho anything more than 0.3 out and it's time to replace .. or clean if you wish and recheck . Car running and in the region of 18kgh .. much lower and air leaks might be the cause .. smoke test for this on the inlet manifold .