S3 1.8t APY Engine: MAF 4 pin???

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Spacecowboy

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Recently came into possession of an early (pre-facelift) S3. Its running rough, done a smoke test and replaced some PCV pipes.

I pulled the MAF plug off to see if things improved which they did so ordered a Bosch replacement. Plugged up today and no difference.

So I thought I'd check the plug connector and to my surprise it only has 4 pins - one is blank.

The MAF that came off has 5 pins as does the replacement.

Is there a specific MAF for this year and engine code?
 

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Spacecowboy said:
Recently came into possession of an early (pre-facelift) S3. Its running rough, done a smoke test and replaced some PCV pipes.

I pulled the MAF plug off to see if things improved which they did so ordered a Bosch replacement. Plugged up today and no difference.

So I thought I'd check the plug connector and to my surprise it only has 4 pins - one is blank.

The MAF that came off has 5 pins as does the replacement.

Is there a specific MAF for this year and engine code?
Click to expand...
MERRY CHRISTMAS
Good evening, I have included a wiring diagram, MAF testing and engine mechanics for the APY and others to assist.
By any chance, is that plug damaged, as it does not look right? all the best @MPH
 

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  • Engine Mechanics AMK APY BAM AUL.pdf
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  • Current Flow Diagram.pdf
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  • Maf Testing.pdf
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Many thanks I'll take a look this evening. It doesn't appear to be damaged - I removed the rear of the plug in case there was a wire hiding but nothing there.

Merry Christmas to you, too.
 
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Spacecowboy said:
Many thanks I'll take a look this evening. It doesn't appear to be damaged - I removed the rear of the plug in case there was a wire hiding but nothing there.

Merry Christmas to you, too.
Click to expand...
PAGE 398 section No 75 in the current flow diagram is where the APY begins to save you, as looking on the pdf
 
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If I've read this correctly 2, 3, 4 & 5 are used but No.1 is fallow which would indicate my plug is correct but the MAF is not?
Screenshot 20251224 222043 Chrome
 
The Audi A3/S3 8L (1998-2003) 1.8T (APY/AMK/BAM engines) typically uses a 5-pin Bosch MAF sensor, with common OE part numbers being 06A906461E or 06A906461M. Bosch units (such as 0 280 218 065 or 0 280 218 381) are the standard. Too much wine now lol, but from what I can make out, 5 pins seem to be correct. I trust you ordered a new one via your original part number
 
I ordered this one:

ebay.us

Air Mass Sensor fits AUDI S3 8L1 1.8 99 to 01 Flow Meter Bosch 06A906461E New | eBay UK

AUDI 06A906461E. VW 06A906461E. AUDI A3 (8L1) S3 quattro Hatchback Petrol 03/1999 04/2001 AWD 20 210 154. Type Mass Air Flow Sensor. BOSCH 0 280 218 034, 0 280 218 035, 0 986 280 211. AUDI TT (8N3) 1.8 T quattro Coupe Petrol 10/1998 08/2001 AWD 20 224 165.
ebay.us

I'll check the part numbers again on the outgoing one tomorrow. But unquestionably, the plug is a D shape 4 pin plug unless someone has, for some reason, yanked out one of the wires. Baffling.
 
MPH said:
Presuming you have done a scan via VCDS, are any fault codes thrown after clearing the existing ones?
Click to expand...
Yes I have VCDS. Original codes were showing intermittent fault with Mass Airflow Sensor and Lambda sensor. Most seemed to be related to low battery. I scanned again today and no engine codes but she is still misfiring.

Comparing the APY diagram with others in the resources you sent over seems to indicate that pin 1 is not used (I.e. 4 pins altogether). So the question is: does it matter if I run a 5 pin MAF?
 
Have you put a new MAF on, I have an AMK engine & it has 4 pins, I’ve got a miss fire too.. had a lot of vacuum leaks, so will now focus on MAF & o2 sensor ( bank 1) wires & fuse


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The 5th pin is for IAT sensor thats fitted to some MAF's... not required for 20v engines

<tuffty/>
 
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<tuffty/> said:
The 5th pin is for IAT sensor thats fitted to some MAF's... not required for 20v engines

<tuffty/>
Click to expand...
Yeah I read that too. I spoke to the dealership and they confirmed what I have is correct for APY so I will go with that. I'm now wrist deep in valve cover gaskets, loom tidying, pipe renewal and general servicing. Cheers for your help chaps.
 
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Jangol said:
Have you put a new MAF on, I have an AMK engine & it has 4 pins, I’ve got a miss fire too.. had a lot of vacuum leaks, so will now focus on MAF & o2 sensor ( bank 1) wires & fuse


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Click to expand...
Yes MAF connected. I've moved on to other potential issues that may cause a misfire.
 
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What’s next on the list??

I’ve done PCV system pretty much, going for a boost sensor next as that’s come up on VCDS


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Jangol said:
What’s next on the list??

I’ve done PCV system pretty much, going for a boost sensor next as that’s come up on VCDS


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Click to expand...
Good luck chap. Let us know when you get to the bottom of your misfire.

For me, I've smoked the system and found and fixed leaks. I'll be checking PCV valves tomorrow and probably just replace the PRV.

If it still misfires after that then it really only leaves injectors or more likely coils and plugs as they have mostly snapped in some way. Oh, and spark plugs. But as I have the valve cover off and the timing belt feels too loose for my tastes, I'll do timing belt, tensioner and pump whilst I'm in there with camshaft seals, both ends too.
 
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Update:

I’m ditching the PCV & going catch can (wish I done that 1st off), as I found another split hose on the main PCV system..

Hoping that gives me the relief required to move onto something else.. feeling like getting a 25 year old car wasn’t the one


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I'm staying stock where I can. Some hoses I have no choice but to go silicone as they are NLA.

Valve cover and tensioner gaskets done. Also a few hoses. Spark plugs, MAF and coil pack plugs replaced. Vacuum hoses done today, a few were disconnected from rotting out. The PCV is an audi part (could be the original) and tests fine. Its running much better now, but...

Its always been a bit 'hissy' at the back of the engine since i bought it in November however now I've done all those bits, its very pronounced. Any clues anyone? I'll post a video.
 
Not sure if this is still relevant (so little forum space compared to adverts :D) but narrow band k04 framed APY / APX MAFs are different to wide band AMK / BAM / BFV MAF and as hoggy said the is not air temp sensor in our MAFs just a space where one can be fitted.
 
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Stuart B said:
Not sure if this is still relevant (so little forum space compared to adverts :D) but narrow band k04 framed APY / APX MAFs are different to wide band AMK / BAM / BFV MAF and as hoggy said the is not air temp sensor in our MAFs just a space where one can be fitted.
Click to expand...
Cheers yes I agree.

With regards to the monster vacuum leak, I've found the culprit

20260112 161901


This connects to the one way valve then into the brake servo. If anyone can identify the part number that would be handy.
 
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It's the other side of this pipe after the 1" connecting hose, just past the silver corrugated heat shield. It's split right where it connects into the check valve.
20260112 181802
 
Stuart B said:
Not sure if this is still relevant (so little forum space compared to adverts :D) but narrow band k04 framed APY / APX MAFs are different to wide band AMK / BAM / BFV MAF and as hoggy said the is not air temp sensor in our MAFs just a space where one can be fitted.
Click to expand...
So to check, the MAF I've fitted and been quoted by Audi to be correct, is correct? I.e. I can fit a 5 pin MAF to my 4 pin harness without issue?
 
That's a really common place and causes middle, loud banging from ignition retardation and sudden solid brake pedal. The TT pipework seems a little better under the brace, but my TT failure was a weird push-fit ribbed cone kind of affair, i think to allow the engine movement not impacting the firewall connections. I just clamped mine past that connection, if you don't know the car's history... someone might have already tried their own repair, I doubt my repair would have lasted much longer than a couple of years due to the motor pulling, pushing and vibrating that connection.
 
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Spacecowboy said:
It's the other side of this pipe after the 1" connecting hose, just past the silver corrugated heat shield. It's split right where it connects into the check valve.View attachment 282922
Click to expand...

Hi could I get some more pics of the location of this pipe please, I think I have the same issue.. be good to see how hard it may be to replace & also the cost for the pipe


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Jangol said:
Hi could I get some more pics of the location of this pipe please, I think I have the same issue.. be good to see how hard it may be to replace & also the cost for the pipe


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Click to expand...
What engine do you have, as I have uploaded a pdfs above for the following engines: Engine Mechanics AMK APY BAM AUL all the best @MPH
 
MPH said:
What engine do you have, as I have uploaded a pdfs above for the following engines: Engine Mechanics AMK APY BAM AUL all the best @MPH
Click to expand...

I have an AMK engine.. will go find that pdf, that you’ve kindly uploaded


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Hose was cracked at the one 1 valve… hard to see until you remove all the pipes out the way…

I’ve replaced with a nice length of silicone hose, will give it a good test tomorrow.. then I can take my time & hunt down an original pipe.. saying that maybe the silicone hose could be a keeper..

Thanks guys for sharing how it was resolved for you..

Just an pre cat o2 sensor the change & car should have no more faults


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