Misfire after aborted scan, ECU comm problems, 2005 S4 Cabriolet b6 8H BHF 4.2 V8

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Uwe

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Jack, what is WD?
See how WD is green and has some dotted underlines? Hover your cursor over anything that looks like that and the forum software will decypher it for you.

-Uwe-
 
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RichS

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Thanks Uwe...this is my first ever forum, thank you for hastening the learning curve. So here is my WD, along with a few underhood pics showing a ground from the ignition harness with compromised wiring. Next step is to test grounds or find a way to mechanically ground terminals 2 and 4 from each coil to the battery...cut and divert the harness? and perhaps find the path to grounds 121, 19 and 343. The pictures may or may not be that ground. Is there any way to find where grounds 121, 19 and 343 are physically located?


 
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Jack@European_Parts

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I always extract the grounds at the coils directly, further a I create a custom bus back to the battery, & that far exceeds the OEM specification for wire size.
 
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   #44  

RichS

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Thanks Jack...I ran separate grounds back from #1, I saw no change in performance though in retrospect i wish that I had used bigger wire...I may try again.
I did measure resistance in all coil grounds (16 total paths) back to the battery, and they were all 0.6 to 1.0 ohms except for cylinder #4, pin 4, which was 0.7 ohms.

I have now noticed that upon starting and running after clearing DTC's, even at idle, it runs great, even cold. It is not until adaptation begins, and the lambdas start to spread negative / positive from one bank to the other that cylinder 1, then 3-2-4 begin to miss. It does not miss at all above 1200 rpm even after adaptation.

I plan to pull the manifold and implement the manifold rebuild kit 079-198-327 or equivalent to get the stuck intake manifold flapper valve to move at 5000 rpm. It will also give me a chance to look in the head to see if there is valve damage evident.If there is a manifold leak at the head, it will also tell me. If there is some mysterious obstruction in port #1, I'll also see that.

Does anyone know if I can remove the manifold without moving the lock carrier to the service position? I have read it both ways.

To summarize to date - this is getting long, I am open to suggestions. Thank you all for the help so far.
Problem started suddenly after DTC’s were cleared from engine- laptop died while doing so
#1 cylinder misses below 1200 rpm
Runs without missing from 1200-5000 rpm
Recent major can-bus work to fix door wiring harness, dry rain infiltration from floor, removed entire interior to fix connections to comfort module, etc. Restored can-bus from single wire operation to two wire, cabriolet top now works reliably. Passenger seat module died from corrosion / short.
Minor indentations through carbon on #1 piston top from intake valves (see pictures)
Compression on all cylinders within 147-165 psi tested cold, most at 160 psi
Injector flow test at factory spec, upper limit though, but consistent between injectors (see pics for spay pattern)
Runs without missing from 1200-5000 rpm
Manifold flapper valve is stuck – actuator attempts to turn it at 5000 rpm, it cannot move
Found and fixed missing injector pintles and resulting vacuum leaks, changed plugs, some improvement
Currently has minor leak from plastic elbow between MAF and throttle valve
Tightened intake manifold bolts – some were 1/16 turn loose to torque
Scans and photos exist in previous posts
 
   #45  

ivagp

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leakdown test on #1, better if u do all or do a runnig compression test. fix leak because its reading false air. is #1 the only piston that has struck
 
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   #46  

RichS

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Aha! one of these things is not like the other one audi S4 B6 cam misalignment

An update - I pulled the intake manifold, un-stuck the variable volume flapper, bought a new PCV (PRG) as the manifold had lots of oil in it, also lots of carbon.
I pulled the valve cover on bank 1 to check cam alignment, and it appears that the exhaust cam lags behind the intake cam by at least one sprocket tooth (see picture).
I found a fragment of chain guide atop the head near the exhaust sprocket (see pic). Lastly, I found a divot in the bank 1 head at the point where the timing chain enters the exhaust sprocket. The chain feels tight, no slack above or below the sprockets.

It appears that someone was here before me, the valve covers have been removed, and the block valley was dated 5/15/2013 with 4 rings. The chain guides that I can see do not appear worn or cracked - but I have not removed the timing chain covers.

I am tempted to re-time the exhaust cam alone, with engine in place. If I can find the service history of the car, and find that someone else has been at the timing chain...so be it. I might still pull everything and go through heads, valve seals, valves, valve springs, chain guides, and more. #1 has two very small divots, 3/8" long, from the exhaust valves contacting the piston. Compression is still acceptable, I may do a leakdown test as well, (yes, I am listening, Jack!) Turning the engine by hand, I get no valve contact with the piston.

The car has no chain noise on startup. It idles very rough. It is (was) smooth at 1200 rpm. #1 cylinder misfires, then bank 1 starts to misfire.

Gentlemen and ladies, thoughts? Can I time just time the exhaust cam to get the alignment slots all to be parallel, so that camshaft locator tool T40046 would fit? Is there a possibility that the adjustor on the intake cam is at fault? Wait, that adjusts relative position of the exhaust cam to the intake cam... I still have too much chain between the intake cam sprocket and the exhaust cam sprocket.

Well, here are the pics...


 
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ivagp

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first things first your welcome. secondly before wasting to much time make sure the valve is not bent, i dont know how your going to do it but you need to do a leak down test on all cylinders. in order to do a leak down your going to find a way to close all the valves on the cylinder your testing, you might have to take off the chain or loosen it. sorry ive mentioned this earlier make sure oil pressure is good, i like to hookup the pressure gauge and drive about ten minutes and the check the oil psi. some like to check volume but ive never checked that maybe jack or someone can chime in on how to check for oil volume. also plan on dropping the oil pan to clean oil pick up tube.
 
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RichS

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Next...

first things first your welcome. secondly before wasting to much time make sure the valve is not bent, i dont know how your going to do it but you need to do a leak down test on all cylinders. in order to do a leak down your going to find a way to close all the valves on the cylinder your testing, you might have to take off the chain or loosen it. sorry ive mentioned this earlier make sure oil pressure is good, i like to hookup the pressure gauge and drive about ten minutes and the check the oil psi. some like to check volume but ive never checked that maybe jack or someone can chime in on how to check for oil volume. also plan on dropping the oil pan to clean oil pick up tube.
I think I can get all the valves closed - they do appear to close. Or maybe I can adjust the bank 1 exhaust cam timing first, hopefully with engine in car, then do a leakdown. Adjusting the cam may be a challenge, as the bolt takes 100 Nm + 1/4 turn to torque. I'm not sure how to hold the cam. I'm not sure if the sprocket pops off by itself when loosened, or must be pulled. I may have to make a special tool to apply the torque without removing the timing cover.

I wonder what else I find in the oil pan...I wish I knew what chain guide that chunk came from. Good idea on checking oil pressure - I have the gauge set from the the work on my other car (an A8 D2).

Long term, I see the engine coming out of this car...it's just too much fun to give up on. And the canbus works without error now. Plus, my six year old picked up a Torx driver and a triple square, counted the flutes, and correctly named each tool, much to my wife's disgust.
 
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Jack@European_Parts

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Note to self ............never buy BHF, unless ran on non synthetic oil, and changed every 3K with proper detergent.

VAG oils and tolerances, are not to be trusted..............last 20 years proves this pretty clear.
 
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ivagp

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i have a friend that has a shop. he had one that needed a chain, i warned him before he started. he'll never do another one. a lot of specialty tools and the whole front cradle needs to come out. book is about 25hrs, if its ur first time double that
 
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RichS

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Re the BHF engine – yes, Jack, I can see that…we did buy this car eyes wide open, knowing that the engine would have to come out some day. Tell me about the non synthetic oil comment, is it because of sludge? I use Mobil1 0w40 currently, I am open to suggestion.

The bank one exhaust cam is 15 degrees different, behind the other three cams. Coincidentally, the sprocket has 25 teeth…one tooth is 14.4 degrees.

I used Snap-On MT 324 leakdown tester with 110 PSI source 9-18-2016. Engine was cold, as it is torn apart right now. All cylinders were within 8% - #1 10%, #5 5%, #4 10%, #8 10%, #6 13%, #3 8%, #7 10%, #2 8%.

I noticed that some cylinders held at 20-30% leakage for a few seconds, then dropped for final reading – is that normal? I zeroed the tester between each cylinder. It appeared to have at least 3-4% deadband, so I zeroed it in the same regulator direction each time.

Next up – drop the oil pan to look for sludge (and tensioner pieces) and to check the strainer per ivagp’s suggestions. The crank is locked in place for cam adjustment. When the engine is back together, I have an oil pressure test kit ready.

I am also refinishing the valve covers – there was big time corrosion. When I media blasted, what was black became deep ruts. It appeared to have a zinc chromate, yellow / green primer, strange choice. Is that factory?

Thanks All.
 
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RichS

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Was the prior owner an A&P or in aviation/military?
Unknown to me. The car had a few owners.
Interesting oil thread. Yes, the oil gets very, very hot - the entire area underhood seems to be far hotter than most cars.

By the way, does anyone know of a self study manual for the BHF 4.2 liter engine? And how to get one?

Thanks, all.
 
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RichS

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well, Houston, a problem...the OEM exhaust cam bolt I ordered from ECS was 125mm long...and has visible runout. The one that came out of the cam was 100 mm long. The ECS bolt does not wind in far enough. The good news is that I think the procedure will work with the right part. Still researching part numbers tonight, off to the dealer tomorrow.
 
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RichS

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Greatly appreciated Jack - is there a self study manual that is specific to the MPI, BHF engine? Or is the FSI engine as close as we get?
 
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RichS

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And in conclusion - the car went back together well, and runs better than ever. The difference in power and smoothness is significant. No sludge present that I can find. No chain rattle, hot or cold. I also had to replace the center radiator, PRG valve, and repair various vacuum leaks. Currently, there are no engine error codes or misfires at all.

I still have to reprogram a new passenger seat controller, and figure out why the passenger side window does not always drop automatically on door opening - but hey, the car runs well. Lots of interior trim to fix as well.

Thanks to all that commented. Your comments pushed me to figure out what was really going on here, and gave me the courage to pull it all apart. I took almost all of your suggestions.

After owner research, I may yet pull the engine. Regardless, I am watching carefully for any sign of chain rattle or misfire, and stepping up my oil change frequency. It appears someone has already removed the engine valley plate, perhaps for check valves, so I am researching that. We anticipate enjoying this car a long time. I won't fear taking the engine out thanks to this experience and your collective insight. Next up - oil pressure test, at some point timing chain tensioner service and perhaps valve stem seals if not heads.

Regards,
Rich
 
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RichS

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I realize now I mistakenly did not post the summary update! I apologize, I thought I did.

The biggest problem was that after sitting for a few weeks, I started the car, and since the cam chain tensioners were not pressurized...one intake cam skipped one tooth, resulting in a 14 degree change in the cam setting. Examination with a camera inside the cylinders of the RH bank showed that the intake valves kissed the top of the pistons, removing carbon but not incurring damage! (It passed a leakdown test). I replaced the cam bolt and re-timed the cam, and all was well. If you make a special tool, this can be done - in my 8H 2005 BHF series audi cabriolet - without removing the engine. You have to lock the crankshaft with a special tool, but you can make the cam alignment tools. Since the repair, there have been 20,000 trouble free miles. I did have to tighten up the intake manifold, repair the variable intake mechanism, and a few other details, so almost every comment was valid - thank you all. Yes, Uwe, Jack, very wonky indeed. Credit also; my Audi dealer, who sends a mechanic out to read my Ross-tech scans at no charge...Phil from Des Moines Audi finally shook his head sadly and said, "It's time you looked inside the engine...valves...". For a 40 valve engine, these words invoke fear.
 
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