Stutter rough idle when first starting car and clears up after 3-4 seconds.

[old guy]

Car has been sitting since noon yesterday.

Battery voltage 12.2 Immediately after start went to 13.9 charging rate.

LPFP primed to 117 psi. Upon starting pressure peaked at 1,275 psi and immediately dropped to 860 psi within the first second.

High idle at 1300 rpm. When idle dropped to 750 rpm the fuel pressure dropped to 570 psi.

[NitroViper]

3 cold starts so far after putting the Coolant temp sensor, k04, and tune. Every one of them bad stuttering for a few seconds. Check engine light went on for a second once. But that's just a misfire code that goes away. Lets hope this isnt a trend because before all that was changed it was just random.

[Smac770]

Some data from capturing fuel pressure and ignition timing from a variety of starts.
red - many hours cold start that had quite a bit of kicking in the first few seconds and then again from time to time throughout the high idle; as always, gets smooth once it goes normal idle
orange - many hours cold start that was plenty smooth
green - about 7 hours since last start, we see it went high idle fuel pressure but warm start ignition timing
purple - about 5 hours since last start, doesn't go high idle
blue - about 15 minute since start, so the fuel pressure starts out around 160 bar rather than the 4.3bar (430kPA) that the others start from

I was experimenting with turbo and group uds and such trying to get a decent fine resolution to the data, but either VCDS cannot do it or the ECM, when sending data through the J533 to the OBD port, cannot do it. You can get lots of samples per second, 30 in one instance, but you just end up with a lot of repeated data values. Thus why there's a lot of horizontal flats to the data instead of sharp points.

First 2.5sec:
first 2.5 sec.jpg

Movement of the FP (fuel pressure) lines from "0" would indicate cranking, movement of the IT (ignition timing) lines from 0 would indicate ignition. I suspect the light purple FP line is late because of the data sample resolution issue noted above. We see red took a longer crank than the others, which I remember being the case. Sounded like 4 cycles rather than the normal 1-2. Still plenty quick to be "in spec", I feel.

We see the two very cold starts burst past 60 bar and then come back down to the high idle 50 bar value. The two cool starts come up towards 50 bar, but then split on their path. Purple 5hr drops down to the standard idle 40 bar (as did the rpms to normal 750rpm, for me), while green 7hr takes its time working back towards 50 bar as it went high idle (1200rpm). Blue doesn't show up yet, it's still falling from that heat soaked 160 bar.

The timing for all goes negative on ignition, does some bouncing around, then we see the two very cold starts head off to the high negative space while the rest are in the mild negative space, eventually moving into the mild positive space.


19-37 sec:
fuel timing mid high idle.jpg

This is really just to show the steady state. We see the green 7hr timing, where it's running high idle, is in the 6-11 positive range. The purple 5hr timing, which is running normal idle, is the same pattern, but in the normal idle range of 0-5 positive. Red and orange are doing their thing in the negative 16-18 space. Notice the wave on that light purple fuel pressure line. Mine has always idled, in the high or normal spec, at around .2 to .05 bar below specified.

First 14 sec:
first 14 sec.jpg

Expansion of the startup to show that transition to the steady states for ignition timing seen in the previous image.

End of high idle:
high idle end.jpg

Here's the end of the high idle, roughly 62 seconds after ignition. High idle doesn't always last this long, but it did in these samples. At the same time that the rpm moves from 1200 down to 750, we see the fuel pressure actually go up from 50 bar to 60 bar. Old guy mentioned that his high idle runs 60 bar the whole way. I assume this is the transition from the catalyst warmup dual injection mode to the engine warmup dual injection mode. It runs along for about 12 seconds that way, before dropping to normal single injection idle mode at the normal 40 bar fuel pressure.

During that engine warmup phase, we see the timing on the very cold starts come up into line with normal. We see the 7hr green, which was looking like normal idle, but at about +6 degrees compared, is now bouncing around a lot before settling down like all the others around 76 sec in.


So the logged cold start smooth and cold start kicking look, in regards to these parameters, the same. The red did fire up the fuel pressure faster, and did take longer cranking to actually fire up, but these caliber of scan tools are not going to provide the necessary resolution to identify any issues. The engine sees 50 bar for high idle average FP, and it seems fine with that. I imagine the higher pressure value for old guy is a tuning change they made with B8.5. Nothing we can do about that without hacking the ECU tune.

The ECU does not acknowledge any misfires during the cold start, so what is the kicking? No idea. There's no way to confirm if it's a crank spin rate issue without a high resolution scope to monitor the crank position sensor signal. All in all, I don't bother with it; it's not impacting the vehicle operation.

[Smac770]

The forum engine needs to stop messing with attachments smaller than 1920x1080. The images seem to be clear enough for the purpose, but they are not as clean as what I uploaded.

[old guy]

Wow! Excellent work as always

I have been observing my cold, intermediate and warm starts for the past week or so. I'm seeing pretty much the same thing that you are recording with the exception of the high idle fuel pressure. On a truly cold start mine stays at ~ 60 bar until the idle drops to normal. Then it stabilizes at ~ 40 bar.

On an intermediate start I believe the residual block temperature determines the advent and duration of the high idle. Sometimes I get a short duration fast idle and other times I get a typical warm start. I need to start recording the temperature to confirm.

I suspect that you are on track with the 60 bar cold start fuel pressure being a B8.5 revision to address some of the stumbling that so many of the B8's seem to experience.

[old guy]

This is interesting. This particular TSB has been showing up on multiple forums when searching for A4 B8 cold start issues.

[Traptalk]

I only see a burst to 50 bar (5 MPa, 5000 kPa, 725 psi) during engine start, and just 40 bar (4 MPa, 4000 kPa, 580 psi) during high idle as well as normal idle.

As for sitting cold fuel pressure, mine will be 4.25 bar (425 kPa, 61.6 psi) before a cool start and as low as 3.25 bar (325 kPa, 47 psi) before a cold start.

What I notice in Nitro's latest video is that ignition timing is really advanced during the stalling out. I don't know if the timing is a reaction to the stalling, or a cause. But on mine, I see only a minor blip to the positive advance just as the fuel pressure hits 50 bar and starts to turn south towards 40 bar. This lasts for only a quarter second. All the rest of the time, my ignition timing is mild negative. As it slows the idle down under 1k, the timing goes and stays mild positive.

I see the timing mild positive but it blips high positive (13.x) each moment the idle drops below 750 (climate system on, A/C off) as it appears to be maintaining rpm in the 750-770 range.

Even once I'm driving, I never see double digit negative timing adjustment except rare blips just above idle (8xx rpm). I do get positive values up to 30.

No idea what A THR is (total harmonic resonance?). Also, how is it attempting to compute vacuum? Did you install a pressure gauge on the manifold?


So I don't think fuel pressure is an issue. It looks fine to me. I might log more with different starts. But it takes an overnight wait to get a cold start with long high idle. Also note, I have a B8.0 CAEB. They might have changed runtime parameters in B8.5 CAEx, or also on the CPMx motors.


fuel temperature - any thoughts on where the ECM is making up this value from? Other VAG vehicles have a G81 fuel temp sensor, but like they removed the G410 low pressure line pressure sensor, we also have no G81. I see nothing in the connectivity of the fuel pump to imply a fuel temp signal is overlaid on the fuel level signal from the pump to the J285 (instrument cluster). I notice that the fuel pressure value is available at all times, but the fuel temp value is only active while the engine is running. Engine not running, value is an immediate -48°C. I assume it's the same kind of phantom bologna as the exhaust temp and exhaust temp before cat, since the engine has zero means to measure those. Unless the 02 sensors somehow rely that value.


As for residual pressure on the high pressure rail after shutdown, 2-3 times idle is not even close. It's over four times. I was at 172 bar (~2500 psi) when I stopped logging at around 25 minutes.

Not sure how fuel temp is measured in vcds but it seems to conflict with the temperature reading from my Bluetooth ethanol content sensor

[NitroViper]

This is interesting. This particular TSB has been showing up on multiple forums when searching for A4 B8 cold start issues.

Hmm my pcv and crank seal are both new.

[old guy]

Hmm my pcv and crank seal are both new.

But not the ECM Flash update?

[NitroViper]

Nope no ecu flash. Ive read somewhere that you dont need it. I dont feel like spending another $150 to test something and it keep doing it. Already wasted $250 on a HPFP for nothing. :(

[Smac770]

Nitro, you have a white cap or black cap PCV on? You just did work on the engine, but prior, did it have a white cap or black cap? I wonder if you have a mismatch to your current ECM tuning. Actually, you have a tune. I wonder how that tune accommodates the adjustment from black cap to white cap.

"We’re following TSB# 2024812/3 for your repairs. The condition is described as an EPC light and idle below 500rpm sporadically at first start of day while stationary, which is exactly your concern. The issue is caused by Engine control module software and the range of crankcase vacuum allowed. The repair includes replacing the crankcase breather valve with an updated part that allows for more vacuum, replacing the front crankshaft seal with an updated part capable of handling the increased pressure, and a SVM (software) update to control the vacuum and resulting readings."

It's probably been in some thread somewhere at some point, but tracking all that down, .... What crankcase vacuum do you read? I wonder if it bounces around on your stalling starts. I would have thought though that they would reduce the vacuum to reduce oil consumption; less pull by the manifold on the oily vapors.

I already have the white cap due to the oil consumption stage 1, so I see the same numbers as old guy for block vacuum at idle. Never watched it at startup.

But do you get an EPC light when it near stalls?

[Smac770]

Not sure how fuel temp is measured in vcds but it seems to conflict with the temperature reading from my Bluetooth ethanol content sensor

Yeah, that's kind of what I'm worried about. No clue how Bosch is generating that value, VCDS is simply reporting the value at that PID. I wish Audi would stop cutting out all the reality sensors.

[NitroViper]

Nitro, you have a white cap or black cap PCV on? You just did work on the engine, but prior, did it have a white cap or black cap? I wonder if you have a mismatch to your current ECM tuning. Actually, you have a tune. I wonder how that tune accommodates the adjustment from black cap to white cap.



It's probably been in some thread somewhere at some point, but tracking all that down, .... What crankcase vacuum do you read? I wonder if it bounces around on your stalling starts. I would have thought though that they would reduce the vacuum to reduce oil consumption; less pull by the manifold on the oily vapors.

I already have the white cap due to the oil consumption stage 1, so I see the same numbers as old guy for block vacuum at idle. Never watched it at startup.

But do you get an EPC light when it near stalls?

I have the white top PCV, I do not have the ECU flash for it. I bought it before I did my engine to see if it helped. I cant remember if it started like crap before I changed it tho.

[Traptalk]

Yeah I thought those white tops were only for the b8.5 or cpma/mb motors 2013+

[NitroViper]

Yeah I thought those white tops were only for the b8.5 or cpma/mb motors 2013+

https://www.rockauto.com/en/parts/%C...eparator,11868

it says its for this car.

Maybe ill just replace it with the black top one

[Traptalk]

I don’t see any fitment info in that link

[Traptalk]

So black top for up to 2012 models and the white top is from that date forward

[NitroViper]

I don’t see any fitment info in that link

you click the part# 06H103495AK and a thing pops up.
FCPeuro has the white top for my 2011.

Easiest cheapest thing for me is to just buy a black top one for my car to see if it fixes the stutter.

[BradyBoi55]

It could be a misfire. If its bad enough it would throw a code for the cel. If its very minor then it is most likely normal. No engine runs perfect. When an engine is cold you see those imperfections because it runs pristine at operating temp. My car has been doing it since I bought it. If its not too bad just keep an eye on it and make sure it doesn't get worse. I was worried about it when I noticed it also.

[NitroViper]

https://www.ecstuning.com/b-hamburg-...YaArqCEALw_wcB

that page says that doesnt fit my car... but thats the one that came off it. Red gasket with white plunger.

[Smac770]

It's been covered before. Audi changed over the PCV from a black cap on the B8.0 to a white cap on the B8.5 (when exactly did they start using white cap on new builds; ECS implies Mar 31 '12). The difference being the tuning for the block pressure.
But oil consumption stage 1 procedure was to replace the PCV with a white cap, and if the vehicle was a black cap, to flash it so the ECU understands the change and also replace the front crank seal (but not the rear crank seal? Bean counters at work).

B8.0 A5 CAEB cylinder head, we see both the A -> E -> AC -> AH black cap line and the J -> AE -> AK white cap line. And the same parts bulletin 1-84 reference that has never been seen here.
https://audi.7zap.com/en/usa/audi+a5.../1/103-103049/

If your engine is the original ECU software, it never had the stage 1 for oil consumption performed, the PCV should be the black cap line.

But now we see those work orders for replacing the black cap with the white cap if there was stalling. Could the white cap without matching flash invoke stalling? I'm not even sure how the PCV would cause stalling unless the diaphragm was tearing. In which case, why not just replace the diaphragm (not that a dealership would do that). Was it necessary to go white cap, or were they just trying to replace the black cap at every opportunity?

Well, we've been waiting for someone with (or should be with) black cap to see if swapping to white cap without the flash causes any changes (issues). If you do throw a black cap back on there, I'd be curious what value you see for block vacuum during idle.

[NitroViper]

Im about to order one of these cheap ass black tops from ebay for $20 just to see if the cold start stutter goes away.... When my cars PCV hose popped off the other day during boost the car rant like crap, it didnt want to start at all and just stalled. That tells my the PCV has a huge factor on the way the car runs and maybe starts...

It's just FCPeuro has 2 different ones with the black top for my engine. The one I replaced had a red gasket with a white plunger, they also have a version with a green gasket and a red plunger. Who knows if mine was already replaced before I bought it.
Like I said, the one I took off had a red gasket and white plunger.

RED GASKET
https://www.fcpeuro.com/products/aud...trp-06h103495e

GREEN GASKET
https://www.fcpeuro.com/products/aud...co-06h103495ak

THIS LOOKS EXACTLY LIKE WHAT CAME OFF MY CAR ORIGINALLY. BUT THAT PAGE SAYS IT DOESNT FIT MY CAR.... 2011 A5 2.0T Quattro
https://www.ecstuning.com/b-hamburg-...YaArqCEALw_wcB

[Smac770]

ECSTuning:
Not sure what ECS is trying to say with "From production date 1/17/2012" for the A5 vs "Fits up to production date 3/31/2012" for the A4. I suspect someone put something in wrong somewhere.

FCPEuro:
E = AC = AH = black cap, and the pics of the red gasket one show a black cap.
J = AE = AK = white cap, and the pics of the green gasket one show a white cap.
I don't understand the confusion.

[Smac770]

https://www.ecstuning.com/Audi-B8_A5...Emissions/PCV/

So they are using a transition date of Jan 16 '12 for the A5. Not surprising, the A5 in ROW came out before the A4 and transitioned to B8.5 before the A4. But I'm pretty sure they have the black cap/white cap backwards regarding which is before and which is after the transition date. Call them up and see if they agree.

[NitroViper]

Im talking about the one I took off originally before I put the white cap on. It had a red gasket and white plunger or whatever you want to call that white circle on the under side of the pcv.

You can see the new white top on the left and my original on the right. The right image you can see the red gasket with white plunger. FCPeuro has 2 different versions as I posted above. The ECS site says it doesnt fit but its the same part number and has the white plunger and alot cheaper than FCPeuro site. So I kinda wanna stick the same exact style that came off the car back on the car.
Im about to buy a no name one on ebay for under $20 lol.

20200519_194517.jpg20200519_194513_HDR.jpg

[JLAllroad]

A few notes

This whole PCV debacle could have been avoided if you would have just answered my question in your original PCV thread.

I wanted to know what part number you had and what you were replacing it with. I asked to determine if either were incorrect for your model/build date understanding the number of revisions over two different paths (black top vs white).

That said without and ECM flash and crank seal (for this purpose) you should have followed the black top path.

“If your vehicle's current breather has part numbers 06H1034695A, 06H103495E, or 06H103495AH "Black Top" then this will be a direct replacement. If you would like to update your crankcase breather to the "Clear Top" you will need to update the front crank seal and update the ECM software level at your local Dealer.”

I know that you are also quoting multiple gasket and valve colors but this is also produced across multiple vendors.

Personally I would stick with OEM given the repercussions of a failure and revision history.

That said, if you purchased via FCP you may want to reach out to see if they will credit you towards an OEM PCV.


Sent from my iPhone using Audizine

[NitroViper]

ECSTuning:
Not sure what ECS is trying to say with "From production date 1/17/2012" for the A5 vs "Fits up to production date 3/31/2012" for the A4. I suspect someone put something in wrong somewhere.

FCPEuro:
E = AC = AH = black cap, and the pics of the red gasket one show a black cap.
J = AE = AK = white cap, and the pics of the green gasket one show a white cap.
I don't understand the confusion.

I dont know why I didnt notice the AK has a white top lol. Confused myself.

That said, if you purchased via FCP you may want to reach out to see if they will credit you towards an OEM PCV.

I bought it from RockAuto, so im screwed there. They dont have anything in stock anyways.

[NitroViper]

https://www.ebay.com/itm/162028750882

thats insanely cheap to just test it out.

[old guy]

Don't waste your time and $$ reverting to a black top. Go back and reread post #166. The TSB indicated that replacing the PCV breather valve with a white top and an ecu update cured the problem. Going back to the black top simply recreates the exact conditions that were addressed by the TSB in the first place.

Here's some additional info on the TSB. It clearly indicates that when you update the PCV breather you need to update the ECM.

[NitroViper]

Don't waste your time and $$ reverting to a black top. Go back and reread post #166. The TSB indicated that replacing the PCV breather valve with a white top and an ecu update cured the problem. Going back to the black top simply recreates the exact conditions that were addressed by the TSB in the first place.

Here's some additional info on the TSB. It clearly indicates that when you update the PCV breather you need to update the ECM.

Ive read #166, its just I doubt they kept the vehicle for a week to see if it happens. Its very random and sometimes itll goes days without it happening. When these cars were new or even years old I doubt they all started having a cold start stutter problem. They add the PCV to try and remedy the oil consumption issue. Maybe they got lucky it if fixed the cold start stutter for some? So reverting back doesnt really scare me because im sure it would last a few years without issues if it fixes it? I doubt all of the sudden id have another oil consumption issue and thats seems like its the only other issue of that PCV? It would be nice to know tho if it fixed it reverting back. Wouldnt know for weeks tho to be sure. Not saying youre wrong or anything, thats just what Im thinking and $20 isnt much of a gamble.

[old guy]

I would rather deal with an occasional cold start stutter than to put on a cheap PCV combination valve. It just isn't worth the risk. A faulty PCV can cause considerable damage depending upon how it fails.

[NitroViper]

I would rather deal with an occasional cold start stutter than to put on a cheap PCV combination valve. It just isn't worth the risk. A faulty PCV can cause considerable damage depending upon how it fails.

I agree but as much as I keep hearing flash the ECU for $150 and change the front crank seal its worth a try to go backwards. I cant afford the $60 for the ecstuning one at the moment. It just sucks I threw almost $250 away on a HPFP as a test. Im to poor to just keep throwing money at it. I dont care if people judge me about that like they have in the past on here. If it fixed the problem atleast we would know what it was.

[dalmation53]

like a rear main seal

I would rather deal with an occasional cold start stutter than to put on a cheap PCV combination valve. It just isn't worth the risk. A faulty PCV can cause considerable damage depending upon how it fails.

[Smac770]

The black cap PCV is designed for a 20 mbar (.6 inHg) crankcase vacuum. The white cap PCV is designed for a 100 mbar (3 inHg) crankcase vacuum. The white cap appears to be yet another design change for the Gen3 which was backported to the Gen2 for/during MY12. It appears at least two TSB actions discuss converting black cap engines to the white cap:

2027731 - Engine oil consumption too high, originated Nov 2, 2011.
2024812 - EPC light illuminated, low idle on first start of day, originated Aug 10, 2011.

Both involve replacing the black cap with the white cap, replacing the front mail seal, and updating the ECM software. Regarding the ECM, my assumption is the increased vacuum will cause increased air flow through the breather valve, resulting in additional air flow into the intake manifold bypassing the regulation of the throttle body. So the ECM needs to know this modified rate so it can manage the throttle body appropriately to deliver the intended total air volume to the valves. I'm guessing at this. I can't see what other impact the increased vacuum would have that the ECM would need to care about. I also have no idea if the breather hole behind the little valve on the bottom is adjusted on the white cap PCV so that the total breather valve air flow is actually intended to be the same under both vacuum levels. But if that were the case, why does the ECM need to know?

For the purpose of 2024812, which I could not find on NHTSA but one incomplete reference seemed to imply it was only for MY11 vehicles, I assume the reason for the change is to make the variations causing the issue to be smaller relative to the overall design. A small issue is a greater percentage of 20 mbar than it would be of something 5x larger, 100 mbar. I for one, had a black cap to 84k miles and never noticed any rough idle, or any high idle "kicking" like I get from time to time these days.

For the purpose of 2027731, I actually can't see how this helps reduce oil consumption. Maybe this is why I never see anyone saying stage 1 solved their oil consumption. The oil consumption issue from rings is oil getting burned up in the cylinder. Is increasing the vacuum supposed to help suck the gasses in to push the oil back in? If the oil consumption issue was excess oily air getting pulled into the intake track, maybe the greater vacuum and likely faster air flow improved the operation of the coarse and fine oil separators?

But if you replace the black cap with the white cap without the software update, I imagine now you have extra air flowing into the intake manifold and leaning out the situation. As closed loop cannot offset that at startup, you end up with lean mix and possible stalling? Same for having the update and trying to go back to the black cap; now you end up rich at idle. NitroViper, are you noticing any lean at idle fuel trim?

2027731 has a chart for black cap vs white cap software:
PCV software versions.jpg

I myself have a 2009 with white cap and VCDS reports ...AL 0001. Note, these replace the ECM updates for the 2027082 for the errant P0234 overboost DTCs.


As an aside, it appears there was a problem with white cap PCVs up through MY14, and a campaign 17F9 occurred in Nov '15. It mentions a diaphragm repair kit 06H198542A:
https://www.genuineaudiparts.com/oem...kit-06h198542a
Curious. It is not relevant to black cap, but I suspect so long as you only use the diaphragm (same recommendation if you were using the Dorman kit), it would be fine.

[Smac770]

I also wonder if you have an abnormal leakage air value (IDE01911). I dug up an old log where I was started up around 3.5 and ran up to as much as 4.9 (kg/hr). This would have been white cap days.

There are also IDE01917 and IDE01918, leakage after and before throttle valve. But these just start 0 and eventually change to -1. No idea what to make of those PIDs then.

[NitroViper]

Smac you make my brain hurt lol. Give me a simple answer, try the black top or not? haha

[Smac770]

What is the software info reported for the ECM?

[NitroViper]

What is the software info reported for the ECM?

I dont have VCDS, I have OBDeleven but that app is such a mess I could probably never find it. Im sure it's never been updated Ill go look tho. Hope my IE tune doesnt change it.

[Smac770]

Another thought; if the source of the idle fluctuation is due to excess air ingestion due to the higher crankcase vacuum of the white cap, remove that as a factor. Unplug the pipe from the PCV to the intake manifold and block off that intake manifold opening. See if your starts are any different. If not, it's unlikely the PCV is involved in the issue, I would suspect. Again, guessing, but it's something to try to add data to the whiteboard.

- - - Updated - - -

https://store.034motorsport.com/chec...di-volkswagen/

[NitroViper]

Screenshot_20200823-184149.jpgScreenshot_20200823-184248.jpgScreenshot_20200823-184338.jpg