# 2.5L 2012 Passat 127k miles, P0305 Only



## Luckranout (Oct 16, 2020)

Cannot get another cylinder to misfire, done almost everything i can, began with spark plugs and ignition coils, no luck then went on to look at intake side and found nothing obvious so decided to replace pcv since it leads directly to cylinder 5 and i replaced the diaphram about year 1/2 ago, Switched cylinder 4 and 5 injector and the misfire is still stuck in cylinder 5, i tried to do a compression test but my **** gauges blew out at 140 where both cylinders 3 and 5 stopped at. anything obvious i can look at ? the misfire only occurs at idle and is intermittent. when i did the valve cover the cam lobes were not scored, yet i did not investigate the valve springs. any advice on small things to look for? i will be compression testing soon once i get proper gauges, i am not burning any oil i lose maybe 1/2 a quart in 5k. should i take the valve cover off again and reinspect the cam lobes / try to see if i can inspect valve springs? anything on the air side i could look for? i sprayed intake down with carb cleaner to check manifold for leaks with no luck. am Stumped Thanks for any input!


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## le0n (Jun 12, 2013)

clamp shut the n80 hose that leads away from the engine.

a faulty n80 could potentially be a source for a vacuum leak.
(it draws air from the rear of the vehicle, so the under-the-hood carb cleaner trick would miss this)


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## Luckranout (Oct 16, 2020)

Unsure if that will help as only cylinder 5 misfires! And at idle when cold it seems. The part is cheap I may go for it but it doesnt seem likely as i feel it would cause a lean condition.


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## le0n (Jun 12, 2013)

you don't have to buy the part (N80 Valve), just test as i've proposed.
sometimes you can just clean it out if there are charcoal bits in there.

if it is faulty (stuck in open position), the temporary clamping of the hose will cure the vacuum leak for diagnosis purposes.

you may get a improper flow error for the N80 valve, but that will go away when you remove the clamp device (small vise grips with two small dowel rods if you don't have the tool)

vacuum leaks anywhere can cause misfires.

this engine can only leaks vacuum from a few places, and this is the more ambiguous place to narrow down.


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## Luckranout (Oct 16, 2020)

I should be more clear of everything I've done and maybe on the issue, but it does not misfire fully just sets the CEL, on the freeze frame the fuel trims are not excessively high only 3% if that, now for the air leak I've sprayed down the manifold with the airbox off and nothing, anything before or at throttle body would cause a lean not just cylinder 5. After compression testing it there Is nothing obvious wrong. I am stumped.


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## le0n (Jun 12, 2013)

Luckranout said:


> ... now for the air leak I've sprayed down the manifold with the airbox off and nothing, anything before or at throttle body would cause a lean not just cylinder 5.


the faulty n80 will leak from the vacuum hose at the back of the vehicle, not in the engine bay.

regardless of leak location, the system may be flagging cylinder 5.

if it is a minor leak, it may not be enough to invoke multiple misfire or even the random misfire codes.

have you tested your PCV again, you stated that you replaced it a few months ago. i don't recall many people having long-term luck with just the diaphragm replacement.
the simple oil filler cap test may give an indication if it is properly venting the crank case vapors.


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## Luckranout (Oct 16, 2020)

Yes everything is 100% sealed up in intake and pcv is also good to go. Sadly with a lil more diag and checking misfire counters cyli 5 is only cylinder every experiencing issues, I put a new intake gasket on because I wanted to Inpsect my intake valves. Atm I'm looking for advice on how to check valve springs, as I'm not sure it would be a lower end issue.


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## le0n (Jun 12, 2013)

find someone with vagcom or equivalent to run a diagnostic scan on the timing.

wondering if it is a chain tensioner issue.

i just realized that a vagcom auto-scan had not been run, or at least you have not stated this.


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## Luckranout (Oct 16, 2020)

That's a big possibility, I guess I have to hang my head and take it in I do not have the tools for timing , and with the cold weather dont think I'd like to time it outdoors


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## le0n (Jun 12, 2013)

i wouldn't jump to this grave conclusion yet, it's just that the early mkv 2.5s had tensioner issues.

search this forum for someone with vagcom in your area.


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## JF007 (Nov 25, 2020)

Hello all, I had to make an account because I’m having the exact same problem. Only code thrown is p0304. My car will do an intermittent misfire at idle when it’s been idling for more than 15 seconds. As soon as you give it gas or if it’s under load, the miss goes away. I’ve replaced all the spark plugs and coils because my ‘11 2.5l Golf has 111k miles. Swapping coils hasn’t helped but injectors are in the mail. Replaced valve cover,gasket,PCV, can’t find any leaks. I’ve done compression test and all cylinders were showing great equal compression. Coil wires look fine and normal for 10 years old. Injector wires in good condition however I have not tested them yet. I replaced dirty MAF sensor. I’ve ran MMO through the oil and gas but nothing I’ve done has solved this issue. I’m going to try blocking off the N80 valve and see if that solves the rough idle. I would also like to note, when the car gives the misfire code, I cannot hear any change in idle or difference in engine noise.

Update: I let my car idle long enough to throw the code and immediately clamped the n80 hose. The flashing engine light did not go away and there was no change in idle or RPM. Does this mean my n80 is stuck closed/clogged?

UPDATE 2: Problem fixed. I’m not sure which was faulty, the n80 valve or the fuel injector. But I’ve driven over a 100 miles since replacing both. Cleared my codes. No engine light has came back on. Misfire at idle gone. Go get a new n80 from your local auto store. I got mine for $26. It takes 10 min to swap. If it doesn’t fix your problem, return it and try the injector...or do both.


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## Luckranout (Oct 16, 2020)

Thanks for your reply, I have since scanned with vag-com and have no luck, only p0305 and it only misfires at idle while the engine is cold. The secondary air system is on my mind, but also trying to decide what would change with a heated engine. The misfires slow down as it heats up. Compression, injectors , plugs and coils all good. The 02 sensors are normal and fuel trims are aswell.


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## Luckranout (Oct 16, 2020)

2 Faults Found:

000768 - Random/Multiple Cylinder Misfire Detected
P0300 - 000 -
Freeze Frame:
Fault Status: 01100000
Fault Priority: 0
Fault Frequency: 3
Reset counter: 255
Mileage: 207463 km
Time Indication: 0
Date: 2034.14.15
Time: 12:22:60

Freeze Frame:
RPM: 796 /min
Load: 34.5 %
Speed: 0.0 km/h
Temperature: 37.0°C
Temperature: 9.0°C
Absolute Pres.: 970.0 mbar
Voltage: 14.224 V

000773 - Cylinder 5
P0305 - 000 - Misfire Detected - MIL ON
Freeze Frame:
Fault Status: 11100000
Fault Priority: 0
Fault Frequency: 3
Reset counter: 255
Mileage: 207463 km
Time Indication: 0
Date: 2034.14.15
Time: 12:23:56

Freeze Frame:
RPM: 775 /min
Load: 30.2 %
Speed: 0.0 km/h
Temperature: 41.0°C
Temperature: 10.0°C
Absolute Pres.: 970.0 mbar
Voltage: 14.478 V


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## le0n (Jun 12, 2013)

I see you're getting the random misfire codes.

Do you happen to have the entire AutoScan results in a text file?


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## Luckranout (Oct 16, 2020)

As in other modules having issues? I do know that there was no other issues except in the engine module.


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## le0n (Jun 12, 2013)

Ok. Just wondering if there could be a grounding issue.

There are specific functions/tests within VAGCOM that can individually test EVAP, SAI, etc.

You can also view the measuring blocks to see Timing, Injector Duty Cycles, etc.

Could be worth taking another peek.


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## Luckranout (Oct 16, 2020)

The timing retardation was looking good,injector cycles might be worth looking into


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## le0n (Jun 12, 2013)

le0n said:


> There are specific functions/tests within VAGCOM that can individually test EVAP, SAI, etc.


these have to be invoked in a separate function outside of the typical code scan/autoscan.

just reiterating...


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## Luckranout (Oct 16, 2020)

I have been trying that, thank you I just can't seem to find anything! I saw information about earlier 2.5s and a ecu reprogram but I doubt that applies.


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