When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello All, I recently Purchased a 2017 970 4S with 38000kms. Obviously was super excited to get the car but that excitement was tainted when the car fluttered, shook and stalled 2 hours into my owner ship. after towing it back to the dealer I bought it from the just to be safe, the car had a bunch of fuel codes which they cleared and all seemed to be fine, only for the check engine light to come on later that same night.
The cars symptoms are:
1. it idles very rough as RPM drops low. when i put it in sport mode and RPM is held higher there is no shaking.
2. noticeable ticking/clicking sound liner to RPM's heard in the cockpit, I'm no expert but kinda sounds like a injector working, may be completely normal.
3. Idk if this can be relate but there was a clanking noise either from the parking brakes under incline pressure at stationary or something else around the time this happened. (again could be completely normal and unrelated, I'm just trying to share as much as possible)
The next day I took the car to Porsche and they took a look at it and came up with the following codes attached in photos below: Porsche say it needs new O2 Sensors (car was sitting for a little bit; Idk if that's relevant information here) but the dealer i bought it from and another mechanic i took it to are saying its fuel pump related and the rough idle and engine light has nothing to do with O2 sensors. in the Screen shots the dealership sent me it does say that the fuel codes are passive and the O2 sensor code is active I've attached a photo of that below also.
I'm stuck between the two diagnoses and i don't know what to do, if anyone can share their insight on this or of they had the same experience i would greatly appreciate it!
its probably going to be related to the fuel pump. Its going to be hard to make a accurate diagnosis without seeing a datalog. Its not going to be that O2 sensor. That O2 sensor does have an effect on fuel trim's but with it being after the cat its job mainly is to monitor efficiency of the cat. It will ask for minor adjustments to fuel trims but nothing that will cause any noticeable difference in how the engine performs. I would try to look at the data log of the fuel pump and look at commanded pressure vs actual and see what you got. Its probably going to be low fuel pressure is causing the issue. That would be where the lean code can come from. If the fuel pressure isn't correct its going to inject a lower volume of fuel into the cylinder than what is actually needed.
The O2 sensor project was a dealer money grab and has nothing to do with this.
First things first. The EA839 2.9 is rough idling engine by its very nature. It is an unbalanced 90-degree V6 with a balance shaft. The balance shaft is a band-aid to attempt to cover the imbalance of a 90-degree V6. All 2.9s vibrate at idle. Some people notice it more than others. I notice it in my Cayenne S 9Y0.1. Having said this, I love the 2.9 in my car.
You have an early build EA839, which unfortunately has a reputation for failed rocker arms in Audi installations. I think there is one EA839 Porsche installation that has recently been identified on this site with a failed rocker arm. Rocker arm roller bearings are the root cause of the failure, and the rollers were increased in diameter in 2018 or so, and there have been few, if any, failed rocker arms reported by Audi or Porsche owners with the later engines.
Then comes ignition and fuel. Fuel pump failures, both high pressure and low pressure pumps, are rare to find reported on rennlist or audiworld for the 2.9. I would not put fuel pump failure at the top of the list. Same comment with fuel injectors - possible but unlikely until you rule out other factors. I am a fan of aggressively replacing spark plugs and ignition coils, and I recommend you do this to rule out variables.
But before you replace any parts, use an endoscope to inspect the rocker arms, and open the oil filter housing to look for metal particles in the bottom of the filter housing. If your rocker arms have smaller rollers, I would follow a diagnostic path for failed rocker arms. If the roller bearings are larger diameter (on a 2017 I don't think this will be the case), I would continue down the fuel pump and ignition components path.
Failed rocker arm resolution path is likely new cylinder heads. The dealer will probably try to sell you a new engine, arguing that metal particles have traveled through the engine. Quite possible, and it would be a judgment call whether to replace the heads, engine or sell the car.
Summary: use an endoscope to see if you have the old or new rocker arm roller bearings. Lots written about this on audiworld includig photos. YouTube has a VW mechanic that is slamming VW for this - turn the volume off an ignore the vitriole, and simply look at the photos in the videos.
Great Insight thanks, I Told my dealer this when I was there and he didn't seem to know how to look that up. do you have any recommendations as to how to find this data? would my normal OBDII scanner work?
09-02-2023, 02:45 AM
HELP!! ROUGH IDLE!
