u/No_Mobile9369

I suppose I may have multiple questions on this… I have a customer that had someone trying to diagnose a multiple cylinder misfire/ poor acceleration/ hard to start. They came to me with new plugs, coils, oil separator/pcv, and new Bosch MAF sensor installed by someone else.

Codes upon arrival

P2177 and p2188 lean condition off idle and rich condition at idle

P0300,1,2,3,4

Hide a cylinder code

P0491 AIR system insufficient flow bank 1

While idling engine vehicle runs great after accelerating short term goes -25% and then vehicle will eventually throw 1 and 4 constant misfire and then extended crank/ hard to start condition thereafter. With spark plugs removed after this condition 1 and 4 are fouled but not wet (2&3 are clean/ appear new), plug / coil swap no change. Compression/ leakage test show no issues/ running compression looks good (I’ve seen bad rocker arm bearings miss a beat,no missed beats seen). Cylinders appear clean not much carbon buildup, intake valves do have carbon buildup on intake side (I do plan on walnut blasting to clean them but I don’t believe this to be main issue). High pressure fuel actual and desired match whole time. Crankcase vacuum at dipstick is around 2-2.5” supposed spec anywhere from 1-3”. Smoke tested crankcase/intake system and no leaks found. 2 odd things seen on scan tool was while monitoring MAF g/s drop to zero at time when throttle snapping (at first snap 0 then up depending on snap, I haven’t seen any read zero before so that threw me off) and also on hard snap there is a pretty consistent double knock/click sound heard at intake camshaft (this camshaft does have the variable style lobes? Is this a normal noise when the actuator solenoids change love position?). It double clicks/knock on start of snap and then when rpm’s drop back down it double click/knocks again which would be consistent with solenoids changing the intake lobes?

I’m suspecting bad injectors for misfires and also performing walnut blasting - any other things I should check/look at/ check

Does that intake camshaft normally make the noise? I had removed solenoids and pcv and used boroscope to inspect lobes as best as possible with no worn down camshafts or abnormalities. All solenoids 7.5ohms resistance and all activates the same when supplying power/ground.

Is maf drop like that on a throttle snap normal?

Wanting to learn as much as possible on these engines as I currently work on almost any make and model that come through the shop. Thanks for any input.

Also first post on Reddit. Google brought me to Volkswagen page when reviewing another’s separate issue. So I hope this is within community rules (thought about the guidelines after typing this out… smh)