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Car (2008 A6 4.2 FSI BVJ) has been running rough for a while, exhaust sounds lopey (aftermarket) and it’s a little shaky while idling. Power doesn’t seem as strong as it used to be either. Was chasing misfire codes for the longest time, been in and out of the stealership a few times. Had a flashing CEL light under hard acceleration sometimes, got codes for random misfire and specific ones for cylinder 1 mostly, once and a while cylinder 2. Have replaced all 8 plugs, coils and even changed the injectors. After plugs and coils the light came on once in a while and after I changed the injectors I can’t get the light to come on, but the car still runs rough. Not getting any codes at the moment but after thumbing through some forums I see that the PCV or pressure relief valve or oil separator (whatever the preferred term is) can possibly cause misfires or misfire behavior. My question is how is it specifically tested? I see a lot of posts about turbocharged engines and a couple NA but I’m still a little fuzzy. I feel like mine may be bad per the videos, but there’s so many contradictory viewpoints out there.
With the car idling I hear the lope in the exhaust, then I unscrew the oil cap (turns hard) and lift. I gotta pull pretty hard to get it off and once it’s removed the car starts running really rough an stumbling bad until I put the cap back on, then it smooths out a bit, but not as smooth as these usually run. One post said something about placing a piece of paper or cardboard over the oil filler hole and if it flutters it’s ok, but if it blows it upward or sucks it down, something is wrong. When I place the piece of paper over the filler hole, it almost sucks it right into the cam cover. Wondering if I’m on the right track because when the cap is off, it just sounds like a more pronounced version of how the car already runs poorly. Anyone else had these types of symptoms? Or does anyone have a 4.2 or 3.2 FSI that can try the experiment I described and see if they’re getting similar or different results? The dealer just charges me a diagnostic fee and swaps around coil packs and plugs each time and tell me they can’t figure out what’s wrong. Been in multiple times and they have replaced the separator plate gasket (leaking), valve cover gaskets (leaking down by spark plugs), oil filter housing gasket (leaking) and an intake port/valve cleaning. Car still runs funny but they’ve ruled out timing chains and components. I myself have replaced the plugs, coils, injectors and at one time the HPFPs (misfire with EPC light and would not go over 3K RPM) and the battery, all OEM Audi parts. The dealership is not that good and that’s a common opinion shared around town. If anyone has any input I’d greatly appreciate it. I have VCDS and a pretty high mechanical skill set but mainly with slightly older domestic vehicles. Just trying to make my my buddy purr like she used to, but these cars can get complicated. Sorry fo the long winded posts, I just try to be thorough so hopefully you don’t have to ask too many questions. Thanks again.
sounds to me that your timing skipped bro.........................
Did you miss a very important oil change or did you allow your ignition coils to go really bad and messed up your spark plugs?
it cost $8,000 roughly to fix that timing jump
I'm curious whether you did some progress with the engine?
I have exactly the same car (2008 A6 4.2 FSI BVJ engine) and I'm trying to solve same symtomps as you very rigorously described.
I bought the car a month ago (originally it was a car, used by Czech Police) and started solving problems of this nice car and engine.
Already cleaned intake valves, replaced injectors and learned a lot from Audi SelfStudyProgramme manual about the the engine.
It's not necessary to describe my engine beaviour, as it really corresponds to how your engine behaves.
I'm only not sure about the exhaust sound, as I don't know how it should sound, but it seems ok to me, both banks are generating same sound from the exhaust.
I noticed that the vacuum under the oil cap is quite strong, and the behaviour when you remove the oil cap, or disconnect the main hose to oil separator...
I'm not sure how strong it should be, so I started thinking about the PCV valve.
And when I started searching information on PCV and the engine oil cap vacuum I found your thread.
I see that replacing the PCV (oil separator) is probably not the solution how to make the engine run smooth again.
I found that the shakes corresponds to spikes in mass air flow chart readings, and ignition timing angle variations, if it runs smoothly for short time, then these spikes are not present.
So I replaced MAF sensor, still the same, so the MAF is not the cause, but the spikes and variations are the result of the issue (charts attached).
Currently I think that the issue may be in the vacuum leak or other issue...
I also think about the worst case... the timing chains, but I still hope, that it's not the case...
Attached is the screenshot of Group 93 Camshaft Adjustment Adaptations, which should show the state of timing chains (from what I've read at various forums).
Bank 2 is not good, but maybe not so bad that its necessary to do the timing chains now...
Could you check your values in Group 93 by VCDS ??
I hope that we can help each other, or someone else, with solving the problem and make the engine run smooth as it should.
I think that the cause is same for both our engines.
Things seemed like they were going good for a while, car was running decent, got a code a week or two ago on my way home from work driving normally, if I remember it was p0456 and something about a “very small evap leak detected”. Googled that and a lot of signs pointed to the N80 valve under the the cover near the oil filter housing. Stopped at an auto parts store, picked one up for under $30, cleared the codes, it didn’t come back and the car seemed to run smoother. Matter of fact, better than it had in a while even though I remember changing that a while back from the dealership’s parts manager’s suggestion. Drove the car normally since then, mostly back and forth to work, seemed fine.
Today I left it at the shop across the street from work for the day so they could diagnose an oil leak. Been leaking for a while and now I can smell it burning while I drive and it smokes under the hood when I pull in the garage. The shop left an estimate in the car for two valve cover gaskets and an oil separator for just over $700. Gonna call them tomorrow and talk with them about it and how they came to that diagnosis because I want to mention that separator was replaced less than a year ago, and the valve cover gaskets about two years ago. Maybe they know something I don’t (which I’d hope so). I’m a decent mechanic, but I haven’t worked in a shop for years. Might be rusty. When I get a chance, I’ll hook up VagCom and compare my values to the ones you posted. Works been busy lately so my free time is scarce. We’ll work towards this together.
Just getting tired of this, I just paid the thing off in June so I’d like it to last a while yet and hopefully have it treat me decent.
I hope too that it’s not timing chains, there’s a couple people around here with these that are pushing 200k miles and they’re doing fine. I don’t miss oil changes, I changed the car with VagCom to set the intervals to 5k instead of the 10k that came from the factory. I change it every 5k with Liqui-Moly Leichtlauf and factory filters from ECS tuning. I also drive it very conservatively, rarely actually using it to its full potential.
I’ll call that shop tomorrow, discuss their diagnosis and go from there. I’m due for another oil change, but I wanted this leak figured out and possibly fixed before I go dump $100 worth of oil and associated items in it.
Thank you for your reply, I'll check also the N80 valve function, it connects the intake with the fuel tank to allow gasoline vapors to be sucked to the intake, if I understand it right.
Regarding the oil leak, when I did the intake valves cleaning and injectors related work, I also did a oil filter housing gasket replacement (seals 079103121BE and N90959701, price fo both 15 USD).
As I've read this is a usual oil leak and smell on this engine (MY photos attached), so if I had the intake manifold out, it's worth it to do the seals replacement.
Could be the same in your case..
It's strange that the shop want to replace valve cover seals and oil separator if you did it recently...
...maybe they think, that you had excessive vacuum in the engine, which sucked in the valve cover seals?
And if the vaccum in the engine is regulated with PCV, thay also think, that PCV is faulty.
But the oil leak must be visible around the valve cover seals to cause smell...
I'm usually trying to find the cause by myself, as the shops usually do a lot of costly replacements, which do not target the real cause of the problem.
Maybe not all shops, but this is my experience with tricky problems.
If you'll have time, please try the VAG, I'm really interested in your values of Group 93.
Do you think the the vacuum in the engine (on oil cap) lowered with oil separator (PCV) replacement.
I'm trying to decide whether to replace it.
Best regards, David
Before cleaning and oil filter housing gaskets replacement. After oil filter housing gaskets replacement.
A couple years ago, the local dealership performed a recall on the catalytic converters, they had to take a majority of the front end apart to do the job. I asked that while they had it that far apart to check for anything else that could use attention while it was accessible. They ended up replacing the oil filter housing gaskets, valve cover gaskets, did an intake valve cleaning, outer tie rod ends, alignment and I think the separator was mentioned as well. I’ll see if I can find the work order invoice. Since then I replaced the valve cover gaskets myself once, the oil separator, check valve (twice), plugs and coils, vvt solenoids and a couple other things. Not sure if these items are prone to constant failure, some other problem causing the failure or if I’m doing the work incorrectly. I’m a former mechanic and spent 10 years working at a Harley dealership, so I know my methods are meticulous and everything is researched for proper torque patterns and specs. I’d like to keep the car because it’s paid off, but with my current job I have very little free time and most of that free time is spent remodeling my house right now. Been contemplating getting a different car, but I don’t want to take on another payment with the house project.
I’ll see if I have some free time on Sunday to hook up VagCom, it’s my only day off during the week.
Today I have come to the conclusion, that the cause of the problem is in the timing chains. I removed the lower engine cover and with the engine running, you can hear the rattling from the area where the timing chains are. The rattle is synchronous with fluctuations in engine operation. It is not very audible from outside the car, but when listening from below it is quite clear. On Monday, I'll start looking for a service to replace the timing chains. The car has 187t miles (300t km), timing chains were probably never changed. The values in group 93 also point to this. I'll let you know how it's going.
I have the non-fsi 4.2 and I can tell you the fix with my intermittent rough idle and missfire codes were due to a bad oil separator, leaking jet pump, and cracking vacuum lines to the egr valves. I also used a DIY smoke machine and ended up resealing my covers and intake.
I bought new vacuum tubing at advance and replaced all the lines and rubber elbows. The heat from the egr cracked the elbows and I could not see it.
The aftermarket jet pump did not feel right, so I epoxied the original and was working better.
The aftermarket oil separator was junk. Got an oem audi and it then ran fine.
The intake and valve covers needs to have new gaskets AND the oem locktite sealer applied or it will leak again.
You can check the timing in block 93 with vagcom. If you have misfires, track if they are in a certain cylinder and swap the coil pack to see if it follows it.
Just some things to check before taking it in and dropping more cash on it.
Thanks raspeita, that’s some good info. I should get a hold of a smoke machine and pump some through to see if it’s got a vacuum leak, could very well be due to the extreme under hood heat these cars can create, I always work on it cold (other than oil changes) because I’ve been burned on things that I would not think could burn. What’s the jet pump you reference? Not familiar with that one.
David, I changed the oil tonight after work (every 5k miles) plus tried to tighten up my steering rack to get rid of some play. Got home and hooked up VagCom to reset the SRI. While it was hooked up, I tried to match your screenshots the best I could. I’m not extremely savvy with VagCom, so I’m sure I did something incorrectly. If I was guided through, I’m sure I could get better info. I took a couple screenshots myself trying to copy what you had and asked. My values look slightly different, the car was running at idle, did not give it any throttle. Was yours at idle? Did you rev it up to a certain RPM? Was the car driven under a load? I’ll post up what I did and you can get or give an opinion on it. Might need a little more guidance.
Also, that rack adjustment I referenced, I got a little turn out of that bolt with an open ended wrench, but I need a little more. Tough to get in there with a tool. Steering wheel has a little wobble, but all the tie rods are new and the u-joints in the column appear tight. Anyone have experience with this?
Last edited by BrandoMeats; 10-29-2020 at 06:44 PM.
Reason: Add info
The top edge where the sonic weld is came loose on mine. I simply epoxied it.
Not sure what your 093 numbers point to but the timing is retarded by around 4 degrees. Someone with more experience in that would have to chime in. I know that before I did my timing guides and adjusters mine was advanced.
10-01-2020, 10:14 AM
