# 1.8t misfires under load



## bvariant (Dec 16, 2003)

(First time, long post here, so please take it easy on me.) I’m trying to diagnose a new hesitation problem when opening the throttle modestly hard under load. It started about 5 days ago and has twice drawn a flashing CEL for 2-5 seconds, though the car feels like it’s running normally at all other times.

The car’s a 2004 Passat 1.8t (4Mo/5M) with 70k miles, an APR93 chip and R1 diverter valve for several years, and stock (PFR6Q) plugs with 14k miles that were regapped to 0.030” when this began. Fuel filter’s 3 years old with 22k miles on it, PCV system was almost entirely replaced (prevention) about 18 months ago and was clean at that time.

The relevant VCDS scans (fault, fuel trims, misfires, pre/post O2 sensors, cat) I’ve done so far are listed below. The things that concern me are noted in italics in the scan results:
a) Misfires, which are spread over all cylinders when logged over a few minutes, though the fault scan notes #4 also. 
b) A pretty sudden, noticeable increase in partial throttle trim (I understand 3.9% is still in spec) from a very solid baseline of 1.8-2.3% during a few years of every few month logs.
c) A cat efficiency number of 4.53: is this even realistic? Especially in light of the “cat OK” diagnostic at the end of the scan?

I’m hoping this is a MAF or vacuum leak problem, though what I’ve read suggests the cat number is very scary. Looking at every vacuum hose (which I haven’t yet had a chance to do, the ones visible from the top are fine) seems obvious. I’m also inclined to unplug the MAF as a diagnostic, since I assume a WOT run for air mass would just give me more misfires and probably wouldn’t be interpretable.

Anything else you guys would try or suggest? Thanks. 

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Summary of results:

1)	fault scan
a.	2012/05/10: _intermittent misfires P0300, P0304_

2)	lambda logging (blocks 014/031/032)
a.	idle trim 0.6%, _partial throttle trim 3.9% (up from 1.8-2.3% at baseline)_

3)	misfire logging (blocks 014/015/016)
a.	2012/05/10: _short runs of 1 to 2 random misfires, all cylinders, but at least half the time with no misfires over 3-5 minutes. _ 

4)	pre-cat O2 sensor test (block 034)
a.	2012/05/10: idle engine speed 800, cat temperature 435C, dynamic 1.616, B1-S1 OK

5)	post-cat O2 sensor test (block 036)
a.	2012/05/10: voltage 0.82-0.84 over 2.5 seconds in time stamp, B1-S2 OK

6)	catalytic converter (block 046)
a.	2012/05/10: 1960 /min Engine Speed (G28), 615.0∞C Catalytic Converter Bank 1 Temp, _ 4.53 Catalytic Conversion Bank 1, Cat B1 OK Cat. Conversion Test Bank 1_

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Fault scan: 
Thursday,10,May,2012
VCDS Version: Release 11.11.3

Chassis Type: B5.5 Passat 4Mo/5M/1.8t
Mods: APR 93 program/APR R1 diverter valve

Scan: 01 03 15 16 17 19 46 56 (only modules seen by VCDS when run from default file)
Mileage: 113070km/70258miles
-------------------------------------------------------------------------------
Address 01: Engine Labels: 06B-906-018-AWM.clb
Part No SW: 4B0 906 018 DP HW: 8E0 909 018 A
Component: 1.8L R4/5VT G 0002 
Coding: 0016701
Shop #: WSC 13112 025 444135
VCID: 72F6D0EB6EB4009

2 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected 
P0300 - 001 - - Intermittent
16688 - Cylinder 4 
P0304 - 001 - Misfire Detected - Intermittent
Readiness: 0000 0000

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Address 03: ABS Brakes Labels: 4B0-614-517.lbl
Part No: 4B0 614 517 H
Component: ABS/ESP allrad 3428 
Coding: 04275
Shop #: WSC 05311 
VCID: 265EFCBBC2FC2C9

No fault code found.

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Address 15: Airbags Labels: 6Q0-909-605-VW5.lbl
Part No: 1C0 909 605 C
Component: 09 AIRBAG VW61 04 0003 
Coding: 12345
Shop #: WSC 05311 
VCID: 245AE6B3B4C0DE9

No fault code found.

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Address 16: Steering wheel Labels: 1J0-907-487-A.lbl
Part No: 1J0 907 487 A
Component: Lenkradelektronik 0005 
Coding: 00118
Shop #: WSC 05311 
VCID: 2F70199FED066D1

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 3B0-920-xx5-17.lbl
Part No: 3B0 920 929 B
Component: KOMBI+WEGFAHRSP VDO V04 
Coding: 15235
Shop #: WSC 01079 
VCID: 265EFCBBC2FC2C9
WVWVD63B24E262539 VWZ7Z0D9169317

No fault code found.

-------------------------------------------------------------------------------
Address 19: CAN Gateway Labels: 6N0-909-901-19.lbl
Part No: 6N0 909 901 
Component: Gateway KCAN 0001 
Coding: 00006
Shop #: WSC 05311 
VCID: F0F25AE3B0B8B29

No fault code found.

-------------------------------------------------------------------------------
Address 46: Central Conv. Labels: 1C0-959-799.lbl
Part No: 1C0 959 799 C
Component: 80 Komfortger·t HLO 0003 
Coding: 00258
Shop #: WSC 05311 
VCID: 376021FF1556A51

Subsystem 1 - Part No: 1C1959801
Component: 80 Tırsteuer.FS KLO 0202 

Subsystem 2 - Part No: 1C1959802
Component: 80 Tırsteuer.BF KLO 0202 

Subsystem 3 - Part No: 1C0959811
Component: 80 Tırsteuer.HL KLO 0202 

Subsystem 4 - Part No: 1C0959812
Component: 80 Tırsteuer.HR KLO 0202 

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio Labels: 3B7-035-1xx-56.lbl
Part No: 3B7 035 180 G
Component: Radio NP2 0016 
Coding: 04031
Shop #: WSC 05311 
VCID: 245AE6B3B4C0DE9

No fault code found.

End ---------------------------------------------------------------------


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## groundnpound (May 5, 2011)

*Misfire Issues*

I have had similar issues, and it was actually 2 separate things. One occurred as a result of my coil pack being cracked. the second was just simply worn/old spark plug wires. Mist of water on the wires while under load showed the shorting THROUGH the 7mm wires. 

Once I changed these 2 things, symptoms went away. 

Now, my issue occurred on a different motor, but these 2 things are pretty easy to check and rule out and wont cost you ALL of your cash.


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## groundnpound (May 5, 2011)

groundnpound said:


> I have had similar issues, and it was actually 2 separate things. One occurred as a result of my coil pack being cracked. the second was just simply worn/old spark plug wires. Mist of water on the wires while under load showed the shorting THROUGH the 7mm wires.
> 
> Once I changed these 2 things, symptoms went away.
> 
> Now, my issue occurred on a different motor, but these 2 things are pretty easy to check and rule out and wont cost you ALL of your cash.


By the way - the cat reading will be WHACKED as a result of dumping RAW fuel into the exhaust during a misfire, so I would not be TOO freaked about that. 

Yet.


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## Anony00GT (Mar 6, 2002)

Check for vacuum/boost leaks. Verify the MAF.

Fix the issues and then re-evaluate the cat. It may be OK (for now), but you will destroy your cat if you don't fix this asap.

Groundnpound, he has individual coil packs (COP), not a single coil pack with wires. They can be swapped to verify though.


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## bvariant (Dec 16, 2003)

Concerning the misfires/cat efficiency number: thanks and duh (my goof), it certainly makes sense that things would not be right. 

It was definitely fuzzy thinking on my part about the misfires, which are at 0 for minutes at a time while idling (you have no way of seeing from my original post). But the cat test is at 2k, not 800 rpm. 

ground, did you also see a minor increase in partial throttle trim before replacing the wiring/coil pack? Thinking through it, I can get as far as misfire--->unburned fuel and increased O2 to precat O2 sensor--->precat sensor sees this as a lean state (since it measures O2 and not HC)--->calls for positive trim. Realistic or not? 

anony, thanks very much, too: I've never seen a glowing cat, but I'm completely on board with avoiding what can happen long before it gets to that point.


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## stan067 (Feb 25, 2010)

Swap #1 coil with #4 clear codes. 
Next time the cel flashes pull codes and see if the miss fire is at Cly #1 or still #4.
If the miss moves to #1 cly replace the coil. Real cheap at dealer! 
May want to see if the coil recall was done? Call dealer give them the Vin.

Good Luck


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## Anony00GT (Mar 6, 2002)

Stan is correct, it only takes a minute to swap coils and verify. IIRC, the recall Bulletin has part numbers for coils that fall into the recall and coils that don't.


If miss follows the coil, easy/quick diagnosis. If not, look towards MAF. Verify no vacuum/boost leaks either way, they're very common on 1.8T's.

Also, after looking at the scan again, I'm fairly sure that 0002 is way behind and you need an ECU software update.


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## [email protected] Parts (Nov 27, 2006)

One thing to add guys.


THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## bvariant (Dec 16, 2003)

You are way ahead of me, but I'm not going to waste what I wrote before the last couple of posts appeared!

-----


Very reasonable, I’ll certainly check coils first since they're easy. I've had three or four (nothing like losing count) fail already, but none in the last 2.5 years so am probably overdue. 

I'd put them farther down the list just now since all my previous ones crapped out catastrophically in different positions with obvious burn marks down the sides; VCDS clearly showed single cylinder failures and less frequent misfires of the other cylinders before I pulled them. (The final couple were so obvious I identified them by shuffling alone.)

I’m currently running a mixture of the last two revisions, which have obviously done better. It makes good sense that they could fail more subtly than the originals, so I’ll let you know if that turns out to be it.


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## bvariant (Dec 16, 2003)

Well, a classic case of over thinking the problem. If you have a 1.8t and misfires, where do you look first? Congrats to the coil pack crowd. 

I thought it might be different this time since my first set of misfires was P0300/P0301/P0304; the second occasion was P0300/P0304 only. But shuffling the coils from 1234 positions to 2143 made things clear. (Logging 014/015/016 under low load said nothing, but putting my foot into it far enough to trigger a CEL gave a clear spike of misfires on the #3 (formerly #4) coil that immediately resolved with throttle off.)

The hesitation's now completely solved with a new coil (one of the two spares I keep around); the problem was in a 06B 905 115R version, which I think is still current for AWM's. 

As Jack predicted, there is a little bit of burning on the #3 and #4 leads of that coil. Also, my last failure was in the #4 position as well. There are still a few low level misfires that I've chased for roughly 4 years, so I'll definitely be doing the requisite search for harness inspection and repair; if anyone has a good link for that and the ground bridge bus, I'd be very appreciative. 

And will look at new cat numbers/fuel trims over the weekend. 

Thanks again.


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## [email protected] Parts (Nov 27, 2006)

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## bvariant (Dec 16, 2003)

My finances aren't particularly flush for the moment, but (particularly if you think it would be of general interest and wouldn't just send people off copying your ideas while you're trying to make a living from them) I would love to see it.


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## [email protected] Parts (Nov 27, 2006)

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## blazerpounds (Mar 19, 2008)

I would be interested in seeing a DIY or make it yourself kit for coil packs.


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## [email protected] Parts (Nov 27, 2006)

We do have individual kits so you can crimp it in.


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## manual_tranny (Jan 7, 2011)

Check the ground on the valve cover for the coil packs. This caused an intermittent misfire around 50-70% throttle and noticeable power loss. The small bolt can come loose from vibration. Fixed my issue.


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