Panelhead

I had a K&N in almost all my vehicles the last 25 years. And I drive a lot, 40 - 60k a year. Never had a problem with engine controls, oil consumption, or any other problems. But after reading of the issues with Audi and other MAF sensors, took them all out.
The fuel filters are now on a three year, 36K maintenance cycle. They are cheap and after freeing up the 10 year old original easy to swap out.
I think mine was original and was clean. But a couple tanks of bad gas and it can plug.

mattsimis

So replaced the MAF and its pretty much the same symptoms, a series of 5 shudders at approx 1900rpm. If you push through it, it will clumsily get above 2100 RPM and run fine. Its also fine from idle to 1900 rpm.

I dont think its a fueling problem anymore (as I suspect I would see other problems too and maybe a DTC) and its clearly not a MAF problem. I think the reason it ran ok without the MAF was that the car acts like sports mode without the MAF, where the revs are generally higher per gear and avoids the problem for the most part.


Things I changed recently:
- Air Filter
- Spark Plugs to NGK BKR6EQUP (3199)
- Oil and Oil filter
- Some vacuum hoses in an attempt to fix this problem
- Fuel filter x2


Again.. there are no error codes in the Engine section aside from the engine mount code (which I cant imagine is the problem as its not at all unsmooth when idling or revving). Can a coil pack (or a bunch of them more likely) die when replacing the spark plugs?

MP4.2+6.0

I skimmed this again. I don't see any codes. Are you sure there are none? In any module? Including tranny one? Many things like coil packs, plugs, vacuum leaks, etc. you can almost eliminate if no codes, so it's odd.

Please confirm you are using real VCDS and scanning across all drivetrain modules. If still no codes anywhere, maybe back to fuel pump questions.

mattsimis

There are no relevant codes, in Engine I have a code for Engine Mount and a check Steering Wheel Control Module DTC, in the Steering Wheel section I have a code for the Cruise Control stalk (it was completely broken off when I got the car, 4 weeks ago, I have an unfitted replacement here). Those codes were there before the the problem started, which was about 1 week after buying the car but after I had given it a service. There is always a zero count in misfire detection. Lambda live reading looks fine. MAF looks fine.

Yes I have a real VCDS and yes scanned ABS, Steering, Transmission and Engine and a smattering of other modules.

Fuel pump aside, isnt the 1900-2000 RPM range also the point where the torque convertor locks and unlocks? The shudder is heavy enough to feel like a transmission "bunny hop".

MP4.2+6.0

I'm not sure where it locks, and mine is a W12 where all is super smooth and subtle. But yes, the RPM range you identify does strike me too as where is may lock. Also k now/remember that the ZF 6 speed is pretty cool and unusual in that it can lock in most any gear, other than maybe first. Most conventional units only lock off the top gear.

Ultimately if you conclude in that direction it may be torque converter, you might entertain a basic fluid change before anything more drastic. Decent preventative maintenance at higher miles/years anyway.

dvs_dave

When you were running it with the MAF disconnected you said the shudder went away, but came back with a new MAF installed?

That means it's not the MAF or tranny and still something with the engine electronics. What does the engine do when in neutral and revved to the problem speed?

mattsimis

Yep, in Sports mode and with the MAF disconnected the RPM is higher and the problem just not there in any meaningful way. Its really evident when cruising.. but actually driving hard or barely moving at all and there is no issue.

When rev'ing the engine in idle nothing of note, no stumbling or other problems.


It looks awkward to strip the intake plastic tubing from the MAF to the TB out.. is it? Id like to check if there is a vacuum or leak there.. perhaps I dislodged something when fitting the new air filter.

mattsimis

Update:

- Checked each vacuum line and every one of them broke once disturbed. Replaced all lines with some rather bling after market tuning. Now have a bucked of old vacuum lines.
- Checked each spark plug to see if any showing any sign of misfire. All looked the same (and were newly put in my me only 3wks ago)
- Reseated the Coil Packs as it looked like 2 of them were not nicely clipped into the wiring harness
- Checked the resistance reading on Pin 2 and 3 of each coil pack, all read 380-400 Ohm between those two pins (and open on all others).

Result: No change, even fixing what was surely a vacuum leak made not apparent difference to performance.


Last night, decided to see if i could change the effect/feeling by swapping the positions of the ignition coils (randomly). Did this and the problem seemed 90% better and my GF says it seemed fixed this morning when she drove it...
I would still like to replace the whatever part if failed though. :|