MAF - 2.8 V6 4Motion

[Scarlet]

I had the following VAG-COM codes - only recently came on.
17532.P1124 Bank 1 mixture adaptation air (add):system too lean.
17534.P1126 Bank 2 mixture adaptation air (add):system too lean.



16891.P0507 Idle air control system:RPM higher than expected



Last week I checked the coil packs and plugs, cleaned the Air Filter & Box, cleared the faults and carried on searching for explanations. This week 16891.P0507 has come back. So I've cleaned the MAF and cleared the fault and will see what happens.

The car's being more thirsty since it's last *********** service and of late has been idling faster and rougher once warmed up. Still goes like the beast it wants to be though.

All the forums fret about the MAF, but if you're not sure and nobody appears to be 100%, is there anything else that could be "clogged up"? Lambdas? Can you tell which sensor a fault code has come form and if so how?

Any advice appreciated.

[Crasher]

There is a pipe that runs from the back of the inlet manifold, almost at cylinder six near the air inlet pipe and the pipe then runs back across the rear of the engine, changes to a corrugated pipe and then into solid again before going into the EVAP canister as a rubber hose. This pipe has a habit of splitting in the corrugated section so check around this for air being drawn in, those fault codes are classic air leak codes. If you disconnect this pipe from the inlet manifold, be extremely careful. The connection to the manifold is a little sod to get off and it is very easy to snap the fitting off of the manifold. If you do this you will be very distressed as the manifold takes a few hours to swap and costs over £500. Before you ask, no it wasn’t me; it was one of my mechanics on my business partner’s car at 4 o’clock in the afternoon on Christmas Eve!!!! By the way, cleaning the MAF WILL kill it.

[Scarlet]

Crasher - you were spot on. Split in corrugated section of pipe. Many Thanks. Car's ticking over smoothly @ 750 rpm, fuel consumption's coming back up. Fortunately appear to not have damaged MAF.

[HOTSHOT III]

+1 for a split in currugated section of the pipe between the inlet manifold and EVAP canister!!

I had exactly the same fault codes as the OP on this thread, in exactly the same order with the same symptoms (increased fuel consumption, idling too fast etc.). Just like the OP I changed the plugs, swapped out some of the coil packs for known good spares and 16891 P0507 kept coming back.

Ross-Tech no longer lists 17532 and 17534 so in desperation I googled them and this thread came up. I've been chasing this for weeks, replaced the split section of pipe in situ using 8mm ID clear braided fuel line and zip ties (took 10 mins), just been out for a 30-mile road test in torrential rain, 750rpm tickover when hot and no EML even after switching off and restarting a few times.

Old (but gold) thread I know but I just had to register on this forum just to say thanks to Crasher and Scarlet for helping me with this. MOT coming up so we'll see if the light stays away.

Thanks again!!

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[Crasher]

Back when these cars were more common that convoluted piping was always splitting. Once when one of my techs was changing one, the plastic fitting on the inlet manifold snapped off.

[HOTSHOT III]

Back when these cars were more common that convoluted piping was always splitting. Once when one of my techs was changing one, the plastic fitting on the inlet manifold snapped off.

I'm really glad you mentioned the plastic inlet manifold in your reply to the OP as the same thing might have happened to me if I hadn't done the repair in situ.

Before getting my 4Motion I had a Mk4 Golf estate with 2.0L AZJ engine. Previous owner broke the check valve which clips on to the plastic inlet manifold next to the dipstick and re-glued it badly, causing the engine to squeak on idle due to a small air leak. I tried to improve it and made it worse, whereupon VW quoted me, yes, £500 for a complete manifold. I was lucky enough to get a complete, good condition used one from a breaker. Took half a day to fit but the car definitely started and ran better afterwards. In those days I didn't have a code reader so it probably threw up all manner of faults.