Misfires: Season B Episode 6

[Spike00513]

Searching,
but requesting help

Progressively, it keeps getting worse. The car has never ran so poorly.

What could it be? Fuel? Air?
Ignition?
Coilpacks were supposedly changed under dealer recall ~60k-mi ago. Doesn't that mean it now has invincible million-mile coilpacks made of unobtanium and angel tears? Or is that false, and they go bad? How?

Everything else seems maintained.
Young O2's. OE spark plugs, gapped. Fresh intake filter.
But, eBay fuel-filter (the 4-prong regulator kind), and stock pump.
I've not yet checked fuel pressure.
An EVAP line is torn so fuel economy dropped, but that shouldn't cause this. Or so I think.

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Seems to like doing it more under load.
For example,
If I cruise on the highway, feels fine.

But load? Bucking/shaking, flashing CEL, and all that.
Bass thud, lopey rumbling. Standing outside the car idling, you can hear and feel it in your chest, and see the engine shaking.
Or, if I try gassing it in high gear, at low speed, such as 4th at 15-20mph.

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I haven't looked at VCDS-log or TorquePro fuel-trims.


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I will CEL/DTC-scan. Should I paint-mark the coils, switch 'em around, and see if it follows?
Throw some NGK Coppers at it bcuz cheap/why-not/get-it-out-of-the-way?

I hear these engines run hot - is that killing the coils?

Thank you

[walky_talky20]

Yes. Even the latest, greatest recall/TSB/Campaign issued coil packs will eventually fail. Just a little slower than the originals. They gradually lose max attainable output voltage with time/heat/miles until they cause problems. 60k sounds about right.

Usually the first indicator is misfires under load, especially under high rpm and high boost on turbo engines. The higher pressure means the air is packed tighter in the chamber. The spark must jump over more air molecules (or something science-y like that) and therefore requires more voltage. If the coilpack can't make enough voltage, you get a nice misfire. Put in a fresh set and you'll likely be all set.

[Spike00513]

Yes. Even the latest, greatest recall/TSB/Campaign issued coil packs will eventually fail. Just a little slower than the originals. They gradually lose max attainable output voltage with time/heat/miles until they cause problems. 60k sounds about right.

Usually the first indicator is misfires under load, especially under high rpm and high boost on turbo engines. The higher pressure means the air is packed tighter in the chamber. The spark must jump over more air molecules (or something science-y like that) and therefore requires more voltage. If the coilpack can't make enough voltage, you get a nice misfire. Put in a fresh set and you'll likely be all set.

So just coils? Not something else also, or instead entirely? Such as MAF?
Fuel pump? Filter?

Looks like it may be 3 misfires. How do you know which cylinder is where?
Audi says 'ignition sequence' is 1-4-3-6-2-5, but that doesn't tell me where those numbered cylinders actually are.
(so that I can paint-mark the CP's and switch them around)

I looked up cylinder-numbering images and the info is conflicting.

[walky_talky20]

Cylinders are numbered front to back, Bank 1 first, then Bank 2. It is an odd numbering scheme, but that's just how Audi does it. This is for the 3.2, but it is the same for 3.0.



And I cannot guarantee it's the coils. It's likely, but there are other possibilities. You can check the coil strength. There is a cheap tool for that. There are also more ghetto-like methods.

[redline380]

cough *MAF* cough

[Spike00513]

16534 - Oxygen (Lambda) Sensor B2 S1
P0150 - 008 - Malfunction in Circuit - MIL ON

16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - MIL ON

16688 - Cylinder 4
P0304 - 001 - Misfire Detected - MIL ON

18339 - Coolant Fan Control Module (J293)
P1931 - 002 - Malfunction - Intermittent

[walky_talky20]

Check your fuel trims. Turn the key on and read block 032.

[Spike00513]

Check your fuel trims. Turn the key on and read block 032.

I just switched coilpacks cyl 4 and 5, to see if the misfire will follow.
In the process, I noticed one of the camshaft-position-sensors (specifically, G301: back of the engine bay near the coilpacks) was broken in half with the connector dangling.
06C905163B.
Whats left of it is dry and brittle, like a stale Hot Cheeto.

That explains the -Open Circuit DTC- that I cleared.
Used=$15, New=$45.
I wonder if that's the cause of all this mess, and if I don't even need a coilpack anymore.

I will check fuel trims like you said.
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What to do. eBay is $25, but the last time I got a (magnetic?) engine sensor from there, the O-ring was a rolled up Post-It note.
ECS $45 is at least Hella. And used will probably have 100k+ mi and break in half in 2 weeks.

[diagnosticator]

It is surprising there is no camshaft position sensor fault DTC.

Replace #4 coil pack, or better, replace all of them with OEM coil packs.

Try and find the fault for the B2S1 O2 sensor circuit, then fix it. That is the post cat O2 sensor, bank 1.

[old guy]

B2S1 is the drivers side front wideband sensor.

[SleeperAvant]

It's shocking how quickly some coilpacks can fail due to heat. Depending on where you are given the weather, those under hood temps can drastically degrade the voltage output of your aging coils.

[MikTip]

Here was my miss-fire cause....

[MikTip]

Fixed my miss fires!