# Persistent misfires on bank 2 all cylinders. Looking for some ideas



## H100VW (May 10, 2001)

Hi, a guy at work recently bought a 2003 A4 with a 2.4 litre V6 BDV engine in it. I came late to this party and would probably have advised against the purchase if I had been consulted.

Anyway, he took it to a local shop as he thought there was a problem with the auto box. It "wouldn't change into top gear". This shop drove around the block and found Bank 2 had multiple misfires in every cylinder when they scanned it. 

Saturday,30,May,2015,10:36:55:07224
VCDS -- Windows Based VAG/VAS Emulator
VCDS Version: 14.10.2.0
Data version: 20150311
www.Ross-Tech.com

Dealer/Shop Name: DMF
Workshop Code: 999 12345 000000

VIN: License Plate: GARYA4



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Address 01: Engine Labels: Redir Fail!
Control Module Part Number: 8E0 909 552 C HW: 8E0 909 052 
Component and/or Version: 2.4L V6/5V G 0004
Software Coding: 0004581
Work Shop Code: WSC 63351 000 00000
VCID: 2E5800FFBA0B7D51CC3-515A
4 Faults Found:

16684 - Random/Multiple Cylinder Misfire Detected 
P0300 - 001 - - MIL ON
16688 - Cylinder 4 
P0304 - 001 - Misfire Detected - MIL ON
16690 - Cylinder 6 
P0306 - 001 - Misfire Detected - MIL ON
16689 - Cylinder 5 
P0305 - 001 - Misfire Detected - MIL ON


Readiness: 0010 1000

The shop replaced the plugs and coilpack but the missing stayed. They were pretty stumped being a generic shop and not a Euro specialist. 

This is where I picked up the ball. It seems to run a little smoother from a start but the miss worsens over the next minute or 2.

The plugs in 456 came out pretty black compared to the ones from 123. Swapping the around made no difference.

The physical timing looks spot on. Certainly if it's out, it's not enough to be causing what I am seeing. Although in the morning I plan to make sure that the crank pulley isn't lying to me about it's position. I'll rotate the motor and watch for #1 rising to TDC.

Today I swapped the injectors side to side, no change. Wasn't really expecting a change. 

I took the cam cover off and checked the timing chain/cam alignment, which is spot on.

I have replaced almost all the vac lines as they broke one at a time as I touched them. :facepalm:

Took off the inlet manifold and gave that a bit of a clean and also examined the inlet path barrel thing. 

When I put it all back together, it did seem to idle a little cleaner but won't rev past 3000 in neutral, just as before.

I forgot to say I did a compression check as well. all good numbers there, especially on 456 180psi.

A couple of things that I have noticed is the exhaust temps. The left pipe seems a decent amount cooler than the right. It also feels like there's less flow, which probably isn't that much of a surprise, if it's not burning correctly?

While poking around with VCDS I noticed that one probe 456? has a really low voltage. A blip of the the throttle causes both to change. Obviously the one with teh higher voltage has more change.

Group A:	'033 
Lambda	Voltage	Lambda	Voltage
TIME 
Marker	STAMP % V % V
0.11	0	*0.045* 0	*0.83*
0.29	0	*0.045* 0	*0.835*
0.45	0	*0.045* 0	*0.83*
0.61	0	*0.045* 0	*0.83*

Misfire counters.

Group A:	'062 Group B:	'016 Group C:	'015 
Duty Cycle	Duty Cycle	Duty Cycle	Duty Cycle Count	Count	Count Count	Count	Count 
TIME TIME TIME 
Marker	STAMP STAMP STAMP 
0.01	13.3	86.7	14.1	7	0.17	*35	220	227* Enabled	0.35	*0	0	0*Enabled
0.52	13.3	86.3	14.1	7	0.69	*35	223	230* Enabled	0.86	*0	0	0* Enabled
1.04	12.9	86.7	14.1	7	1.21	*35	226	233* Enabled	1.38	*0	0	0* Enabled
1.55	12.9	86.7	14.1	7	1.73	*35	229	237* Enabled	1.9	*0	0	0*Enabled
2.07	12.9	86.7	14.1	7	2.24	*35	232	240* Enabled	2.4	*0	0	0* Enabled



I can disconnected either B1 or B2 probes and the ECU notices straight away. I am surprised that the ECU hasn't called the output low? It's indicating a massive rich mixture I think. The exhaust doesn't smell rich, nor are the plugs as black as I would expect.

I can't find any vac leaks.


So does anyone have any ideas? So weird that 3 cylinders are afflicted. :screwy:

Thanks for any help you guys might offer.


Gavin


----------



## O_o (Nov 12, 2009)

I don't quite understand your VCDS log (not clear which signal is which in the 1st one, and I have no idea what column is what in the 2nd). However, I'd guess that the driver's side catalytic converter is blocked. Misfires on one bank only are usually because of an intake or exhaust problem, and since you noted the bank 2 exhaust seems not to flow much (although, I thought there was a cross-pipe between the two sides --- ??), it seems logical to start looking there. An intake leak is a possibility, but would lead to a lean condition, whereas you seem to be running rich (black plugs). Either way, I'm surprised an O2 sensor isn't barking at you....

Also, was there oil in the plug wells when you checked them? Cars of this age are prone to PCV failure, causing oil to seep through the valve cover gasket. Seems odd that it would only be on one side though, unless the breather is blocked. I can't remember which way the PCV flows on these, so that might not even make sense. Which side has the PCV valve again? Driver's?


----------



## H100VW (May 10, 2001)

O_o said:


> I don't quite understand your VCDS log (not clear which signal is which in the 1st one, and I have no idea what column is what in the 2nd). However, I'd guess that the driver's side catalytic converter is blocked. Misfires on one bank only are usually because of an intake or exhaust problem, and since you noted the bank 2 exhaust seems not to flow much (although, I thought there was a cross-pipe between the two sides --- ??), it seems logical to start looking there. An intake leak is a possibility, but would lead to a lean condition, whereas you seem to be running rich (black plugs). Either way, I'm surprised an O2 sensor isn't barking at you....
> 
> Also, was there oil in the plug wells when you checked them? Cars of this age are prone to PCV failure, causing oil to seep through the valve cover gasket. Seems odd that it would only be on one side though, unless the breather is blocked. I can't remember which way the PCV flows on these, so that might not even make sense. Which side has the PCV valve again? Driver's?


I just cut and pasted the text and it screwed with the formatting.

In the first section, I just bolded the lambda voltages. The car is RHD but the #2 bank doesn't change, still 4, 5, 6. So the voltage is way down on that side but still changes slightly when you rev the engine. Like you say, it's well rich.

The car had new cam cover seals before I became involved, to get a roadworthy ticket. Not at a Euro specialist though as they didn't change the plug facing the firewall, which is still leaking like a champ on both sides.... 

The bold numbers in the second section are the misfire counts, they were increasing all together but after I pulled the intake manifold for a look one cylinder seems to have improved. Not sure if it's relevant to your thinking but on a cold start, it runs much cleaner and only starts shaming visibly after 30 seconds or so. 

I have a shufty scope and will try and have a look down the pipe through the lambda probe hole, if the rain ever dries up in the Sunshine State..... Queensland :laugh:

Thanks for you input, much appreciated.

Gavin


----------



## O_o (Nov 12, 2009)

LOL. I completely misread your post. Low lambda voltage indicates a lean mixture, but when it's that low, it could also be a failed sensor. The latter makes sense, since on a cold start, it runs in open loop, ignoring the O2 sensors. Also, when it's warmed up, it will trim as rich as the ECU will allow, which would explain the black plugs. Try testing the B1 sensor, or swap it with B2 and see if the misfires follow. Also, is it the front or rear sensor? Looking at the log for the other one might also provide a clue. 

If the sensor checks out, then I'd say you may have a leak in the intake manifold or runners. If it really is that lean though, you've got a pretty big leak, and it would be very surprising that you hadn't found it already.

The oil coming from what sounds to be the half-moon seals is definitely not normal, and indicates a blockage in the PCV system. It's also possible that oil is leaking into the combustion chamber through the inner gaskets, causing misfires and plug fouling.

By strange coincidence, while you're having a soggy winter down in the Sunshine State, we haven't had a drop of rain in nearly two months here on the Wet Coast. It's only June, but the grass is already dead!


----------



## H100VW (May 10, 2001)

O_o said:


> LOL. I completely misread your post. Low lambda voltage indicates a lean mixture, but when it's that low, it could also be a failed sensor. The latter makes sense, since on a cold start, it runs in open loop, ignoring the O2 sensors. Also, when it's warmed up, it will trim as rich as the ECU will allow, which would explain the black plugs. Try testing the B1 sensor, or swap it with B2 and see if the misfires follow. Also, is it the front or rear sensor? Looking at the log for the other one might also provide a clue.
> 
> If the sensor checks out, then I'd say you may have a leak in the intake manifold or runners. If it really is that lean though, you've got a pretty big leak, and it would be very surprising that you hadn't found it already.
> 
> ...


Thanks for taking the time to reply. Brisbane airport was gripped by fog yesterday and the planes were diverted all over the place. So I missed out on an opportunity to have a look at the car again. Couldn't get up to my elbows in it with aircraft still to see. 

The owner really needed to get it fixed, so has had it towed. I'll chase him to find out what the result is.

I'll also pass on your ideas in case they lead to a fix. 

Usually our grass is dead through winter, as all the rain comes over summer. Not this year it would seem. :screwy:

Cheers

Gavin


----------



## O_o (Nov 12, 2009)

I hope he gets it sorted out, and it doesn't cost him an arm and a leg. If it does turn out to be an exhaust leak, you should tell him not to buy OEM replacements. They'll probably cost more than the car is worth.

Finally got some rain on Thursday. Not nearly enough to make it green again though.

Cheers.


----------



## H100VW (May 10, 2001)

O_o said:


> I hope he gets it sorted out, and it doesn't cost him an arm and a leg. If it does turn out to be an exhaust leak, you should tell him not to buy OEM replacements. They'll probably cost more than the car is worth.
> 
> Finally got some rain on Thursday. Not nearly enough to make it green again though.
> 
> Cheers.


The word is, the cat was blocked on that side and the other wasn't far behind. It's getting "fixed" on Monday. 

Gavin


----------



## Armagon (Apr 19, 2004)

Have the same problem here except that the car is a customer's. The problem was on bank 2 misfire on cyl 4-5-6

I change the cam tensioner and the chain. 
When removing all I took note that the chain had 14 rollers between the 2 marks. So I thought that I found the source of the problem. So I Put it all back together with new hardware and it was worst. I took the compression, 130 psi on 4-5-6. After I got the code p1347, I browsed RossTech to find this :
http://wiki.ross-tech.com/wiki/index.php/17755/P1347/004935

It was saying a different thing than the Bentley was specifying. So I removed the cams again and redid all as on the picture in the link. The engine runs better although it get misfire on cyl 4-5-6 still and I checked compression and I have 180 psi on all 3. Funnily I have 160 psi on 1-2-3 cylinders.

I drilled a hole in the downpipe on bank 2 cylinders to see if the cat is blocked, but it didn't help anyhowm I still have the same problem. No power and misfire on 4-5-6 cylinders.

Don't know what to do anymore.


----------



## H100VW (May 10, 2001)

Armagon said:


> Have the same problem here except that the car is a customer's. The problem was on bank 2 misfire on cyl 4-5-6
> 
> I change the cam tensioner and the chain.
> When removing all I took note that the chain had 14 rollers between the 2 marks. So I thought that I found the source of the problem. So I Put it all back together with new hardware and it was worst. I took the compression, 130 psi on 4-5-6. After I got the code p1347, I browsed RossTech to find this :
> ...


I did all that too mate and it was a blocked cat on that side. The other was on its way to the same result. It would barely rev at all and with the downpipe disconnected from the manifold it was all good.

We just knocked the guts out of it and the car has been running fine since.

Gavin


----------



## Armagon (Apr 19, 2004)

I removed the o2 sensor from the bank 2 and it still gives me misfires like I never did anything. That's the thing I can't get over.
I just tried new plugs this morning just in case and no change at all. 

Mine, I can drive it up to 120 km/h, I can rev it to 5000 rpm, t just has no power. And now that I removed the o2 sensor, it does the EXACT same thing. 
Thanks for you advice though.
The chain was like on top of the first picture and I re installed it like on the second picture, in the bottom. The compression changed from 130 psi to 180 psi on all 3 cylinders of the bank 2


----------

