Mop

Hey Folks,

So I've owned a used 2012.5 991.1 C2S (non PSE, PDK) for 2+ years now. Recently hit 75k miles (bought with 42k in 2018) and haven't had major issues / unfixable issues til now. I had a major service performed by a reputable indie nearby at around 55k miles. Have had oil changes on schedule. Also, I'll post up a rough guide on swapping out the VVT solenoid at some point as there didn't seem to be a reference on the forums already (for the 991.1 series at least + thanks to VII7 for the help!)

Hoping to get some insight from those who have more experience with 991 misfiring issues I'm seeing:I've done a ton of lurking and reading and I completed the below: Unfortunately, after doing all this, I went for a somewhat spirited drive on the highway and easily induced the shudder/vibrating misfire issue again with the flashing yellows stated above. FEC is still permanently on. The only things I can think of now are:The weird thing too is that sometimes on a very smooth road and driving straight (with little road vibrations), the engine seems to pull very smoothly with no issues. But it seems vibrations aggrevate the issue.
My plan is to get another full diags check with the indie shop and possibly try another. But after that, I think I might need to cut my losses and sell the p-car for a discount sigh...
Any info would be greatly appreciated as I really do not want to resort to dumping the car and taking a loss on it to buy something else. I also am not a mechanic / an expert--

Thanks!
Steven

Here are some ref photos below of the wiring situation:
Wiring on a nearby part next to the coils

New .03 Solenoid going in:

981KMAN

Just out of curiosity,.... when you changed the ignition coils, what brand & revision did you use? Did you change them or did your Indy Mechanic?

The P1433 is a Vacuum System Fault - which may lead you to the know Change Over Value issue, where coolant leaks onto the Vacuum manifold and screws up several COV's.

I am not familiar with the P10XX codes. Can you list what these actually?

polobai

My guess is a loose connection or harness issue-looks like you have already replaced everything else...No mice damage right?

Mop

- Yeah should be no mice. Car has been driven as a daily, stored in a garage, and no indication of rodents (urine / fur / seen anything)
- My concern is the amount of labor and cost associated with swapping out the entire engine harness. Doesn't sound like something the avg DIYer could do haha-- Any way to check (know good probe points?)

- So I personally switched out the ignition coils. But the indie did do the spark plugs prior and I didn't see anything out of the ordinary. Perhaps a mismatch in OEM vs Porsche parts would be a concern? This was done last month with BERU OEM parts I bought off FCPEuro: BRU-ZSE052
https://www.fcpeuro.com/products/por...kt#description
- Ah yes thanks for pointing that out on the COV / vacuum leak. Actually my car did suffer from that fault earlier this year with the cooling systems (exhaust valves stuck open + fault). The indie shop did repair and swap out my COVs (3x of them seemed bad) which addressed the fault. Apologies, mixed up the two code pages. Sadly a lot of issues with this 991.
- As of now, I only see P0305 (Cyl 5 misfire) and U0418 (PSM control unit memory fault) when the shop pulled the codes again this AM (thanks RMG enterprises! Would recommend if you're in the bay area)


As a brief update, I visited RMG this morning and they pointed at potential carbon build up? Likely will do a diags with the dealership now--

To note, it's weird that the P0305 cyl 5 is the only code displayed but with a reader, my shop was able to pull the following:
- M310_Misfire counter, 10 trips, cylinder 1 = 12
- M320_Misfire counter, 10 trips, cylinder 2 = 13
- M330_Misfire counter, 10 trips, cylinder 3 = 9
- M340_Misfire counter, 10 trips, cylinder 4 = 6
- M350_Misfire counter, 10 trips, cylinder 5 = 37
- M360_Misfire counter, 10 trips, cylinder 6 = 14

It seems all cylinders are misfiring yet cyl 5 is significantly higher. The only thing I would relate this to would be maybe me switching out cylinder 5's sparkplug again specifically? Would torque spec or swapping only a few spark plugs actually be a noticeable difference?

Thanks a ton for the input!

Joec500

Would bore scoring cause these types of fault codes? Otherwise I have 80k+ miles on my motor and have yet to have any issues related to carbon buildup.

981KMAN

So this issue happened about 20K miles after the major service, and all the Ignition coils were replaced after the problem started..... yet did not solve the issue... Correct?

Cracked or Bad ignition coils / spark plugs usually appear in one or two cylinders, yet you state issues with all 6 cylinders. Obviously Electronic Ignition issue. I like your idea to let the Dealer figure it out.

Best of luck.

Mop

- Good to note. Yeah scouring the forums, hard to find similar cases or anything regarding carbon build up
- Really hope it's not bore scoring. Sounds like I'd need to bore out the engine further or get a new engine haha.

- Yeah that is correct. 20k after major sounds right for the issues appearing. And ignition coils did not fix.
- Sigh sounds like itll be dealership. Unfortunately im part of the "can afford a used 911 but dealership pricing is too much" club.

Thanks for the help! Will update the thread later incase it helps someone else down the road--

GONEIN10

your P1041 and P1044 relate to fuel injectors 1 and 4. The P1433 is fuel pump related. You may very well have had a bad batch of fuel and have contaminated the injectors.
Flow rates can be monitored via scan tool diagnostics. If this is the case you would be able to have the injectors bench tested to confirm flow. If the scan tool shows a variance in fuel delivered but the injectors check out OK via bench testing then the culprit may very well be the ECU as this is where the injector drivers are located.
I would also check the fuel rail pressure regulator with the scan tool.

Mop

- Thanks for pointing this out. Will def mention this to the Porsche tech (appt in 2 weeks LOL). I'm kinda hoping the change-over-valves that failed and got replaced took care of these P1xxx codes
- Think running Techron fuel additive through might make a difference? Guess it couldn't hurt so i'll just give this a shot--

991.1 Guy

My friend had a similar issue. We change plugs, MAF, coils, injectors, etc. It ended up being a faulty fuel pump. You might check fuel pressure.

GONEIN10

I don't believe fuel additives would help. I'm inclined to think that fuel issue is definitely the problem. The fuel pump code you have is for high pressure it would lead me to believe that the fuel pressure regulator could be the problem. Hope you get it resolved and that they let you know exactly what the problem was. post back and let us know

Joec500

Hmm the fuel pressure pump sounds like it could be a real possibility. I had similar codes and issues when I had my old N54 powered BMW 335i, which was notorious for HPFP issues. Hopefully it's a matter of a relatively simple component swap.

Mop

- That does seem to make sense and sounds like a good route to go down. Thanks a ton for the input!
- In that case, the plan is to communicate this with the Porsche tech, but i'll see if i can do voltage drop test + pressure hold test on the FP.
- Dumb question, is there a good resource to check Part number list and locations? Can't seem to find straightforward guides on 991 specific setup. I hope it's similar to the 996 and resides both in the front. Seems like on the 996, the FP is coupled with the sender? Sender = Regulator? Can't find appropriate Part Numbers haha--
- And yeah for sure, i'll keep this thread updated for future ref--

- Good data point. Seems to be in line with GONEIN and Joec's recommendations regarding fueling. I'll likely do a pressure test.

- Got it, thanks! Do you reckon it'd be a bad idea to putt around in the car still with a faulty FP? It's my only car/daily. I assume the misfiring wear caused to the engine or other components would be negligible.

Mop

So funny thing happened. Thanks to GONEIN, 991.1 guy, JOEC, and everyone!

After using Techron Fuel System Cleaner, the Check Engine Light (Fault Engine Control) actually went away after about 20ish miles of driving. Seems the engine rev's out a little smoother but there is a somewhat still noticeable shudder during some roads / acceleration pulls. I think all the suggestions regarding fueling seems to be aligning. Plan to get the diags run with Porsche on 1/18 and hopefully it'll point to a faulty fuel pump or regulator. Or if I can get to it myself sooner, I'll try a pressure test this weekend and see what the V drop across the two components are.

Will update down the road when I find out-- Thanks!

Mop

Hey folks, just closing the loop here and providing an update incase it helps others--

After a week of back and forth with Porsche of Redwood City in the bay area (would highly recommend, I worked with Greg from the service department and the service and attention to detail was impeccable. Did not attempt to sell me unnecessary things and helped to explain everything to a tee. As well as chatted with Michael, the service tech, who provided insight):
- Turns out, after another sparkplug and coil swap, which helped for about 2 days, the issue sprung up again specifically for Cylinder 5 misfiring (CEL, PSM, Start/Stop failures/lights). They were able to reproduce the issue in the shop and seems to be coming from the LIFTER/CAMSHAFT which points to an internal engine issue. There is a well defined lifter tap from cyl 5 and their guess is that it is gunked up and not opening/lifting as designed, hence, fuel additives seeming to temporarily help with the issue. Unfortunately, they would need to disassemble the engine to confirm this which would be an extensive job. At that point, it would make sense to make the swap out but at a cost of ~$9k. I called up some indies to see comparison but they pointed out some important factors: engine reassembly is a difficult job with high risk, mistakes can be catastrophic and 2 of them declined to even attempt/quote the job. Plus porsche dealership would offer a 2 year warranty on the parts itself.

Now just at an impasse with what to do:
- wholesale for a loss and just accept it
- continue to use fuel additives to see if it can help with the gunk assuming its the issue and continue driving
- repair, but i dont see myself forking over 9k. Might make more sense to move to a cayman gt4 or another 911 at that point.

Thoughts?