# Misfire, rough driving, CEL and P0304 - 2007 VW Jetta Wolfsburg (2.5L)



## rdy105 (Apr 30, 2013)

SOLVED: I replaced the fuel injectors and it runs perfectly. No codes, no hesitation, no misfires!

Hi all -

I posted this in the model specific forum, but it was suggested that I post it here, too. 

http://forums.vwvortex.com/showthread.php?8186705-Misfire-rough-driving-CEL-and-P0304-2007-VW-Jetta-Wolfsburg-(2-5L)

I've been trying to troubleshoot this issue, and am looking for some guidance. My 2007 VW Jetta Wolfsburg Edition (2.5L) recently did not start. I've been having issues with the fuel gauge where it would display empty sometimes, usually on really hot days. I let the gas tank go down too far, and this past Monday it wouldn't start. I'm fairly certain that it wasn't completely empty, but when I added some gas it eventually turned over and started. When it did, the idle was very rough, and I got a CEL. I pulled the code, and it showed P0304, cylinder 4 misfire. I have a cheap scanner tool I used to clear an airbag code, as well as a bluetooth scanner and the Torque app. Both only show P0304 - even after swapping coil packs and changing plugs. Here's what I've done so far:


 Added fuel injector cleaner (cheap stuff from the gas station) and 93 gas (usually use 87) - no change
 Bought a new ignition coil, and swapped it with each one installed, one at a time, to see if one was bad - no change, same CEL and code
 Swapped the spark plug from cylinder 4 with cylinder 3 - no change, same CEL and code
 Changed all of the plugs with new NGKs - no change
 Installed new fuel pump (Bosch) - no change
 Added Berryman B-12 to the tank, and filled up with 93 - no change
  Installed new fuel filter - no change
 Used low voltage tester on ignition coils and injector wires
 Measures the resistance of the injector on cylinder 4, which was within range

Plugs were changed (NGK Platinum) in March 2015 (since changed again), and have about 20k miles on them. Ignition coils (OEM VW) were changed in August 2015, and have about 15k miles on them. Fuel filter was changed in August 2015, as well (since changed again). Check MAF, looks clean.

I'm wondering if the low fuel situation clogged up an injector, and that's what is causing the misfire??? I appreciate any and all input I can get! Please let me know if you need additional info.


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## le0n (Jun 12, 2013)

low fuel situation won't clog an injector. your fuel filter takes care of this.

swap your n80 purge valve. reset codes and test.

hard starts (especially after opening the gas cap for fueling) is a symptom of a bad/failing n80 valve. they're usually damaged when people top-off the fuel tanks by repeatedly clicking the fuel nozzle trigger to get as much gas as possible in the tank.

cheap and easy to swap.


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## rdy105 (Apr 30, 2013)

le0n said:


> low fuel situation won't clog an injector. your fuel filter takes care of this.
> 
> swap your n80 purge valve. reset codes and test.
> 
> ...


I considered this, too, but I never top off when I fill up, I don't have any hard starts after filling up, and I'm not getting any codes other than P0304. Though, I'm willing to try it out this weekend - like you said, easy and cheap.


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## le0n (Jun 12, 2013)

you could just clamp the vapor hose shut to test it. this can be done without even taking the engine cover off.

clear codes with Torque, N80 clamp vapor hose, start the engine and let it idle for about five minutes.

if no misfire faults are triggered, take it for a drive (securing whatever clamp you have in place before hand) to see if any faults get set.


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## rdy105 (Apr 30, 2013)

le0n said:


> you could just clamp the vapor hose shut to test it. this can be done without even taking the engine cover off.
> 
> clear codes with Torque, N80 clamp vapor hose, start the engine and let it idle for about five minutes.
> 
> if no misfire faults are triggered, take it for a drive (securing whatever clamp you have in place before hand) to see if any faults get set.


No change. Still P0304 code.

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## le0n (Jun 12, 2013)

then it's not your n80.

in your freeze frame data, when it the code being triggered? at idle?

what do your fuel trims look like in Torque? high negative or high positive fuel trims can give leads in diagnosing.

what are at your Short Term Fuel Trim data at idle?


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## rdy105 (Apr 30, 2013)

le0n said:


> then it's not your n80.
> 
> in your freeze frame data, when it the code being triggered? at idle?
> 
> ...


Code is triggered at idle. Also see misfires in cyl 5, but must not be enough to trigger a code. I'm new to Torque, but from what I can tell the fuel trims are 0. 

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## Jamesmk5 (Aug 21, 2015)

Move that injector to cyl 1 and see if it changes


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## le0n (Jun 12, 2013)

rdy105 said:


> Used low voltage tester on ignition coils and injector wires
> * Measures the resistance of the injector on cylinder 4, which was within range*


did you measure all of them for a relational comparison?

just because you get a code for a specific cylinder, it does not mean that the problem exists at that cylinder. it could be a random misfire scenario.



rdy105 said:


> Code is triggered at idle. Also see misfires in cyl 5, but must not be enough to trigger a code. I'm new to Torque, but from what I can tell the fuel trims are 0.


you're not going to have a "0" reading on your Short Term Fuel Trim if you are getting any misfire codes, pending or not.

example of *STFT1* at idle:
also note the AFR(m) (Air/Fuel Ratio - measured)









post a screen capture of your torque dials.


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## rdy105 (Apr 30, 2013)

At idle:













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## rdy105 (Apr 30, 2013)

Rev at 3k RPM:










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## le0n (Jun 12, 2013)

^^ something is not right. your short and long terms are not fluctuation at all. i can see the high and low marks (orange and red arrows) have not moved off of zero.

i wonder if they are designated with a different name on your ECU, being that mine is a 2009.

look for other PIDs that would give you these readings.

AFR is reading, but it is a little higher than it is supposed to be.

per wiki: "Air-fuel ratio of 12:1 is considered as maximum output ratio, whereas the air_fuel ratio of 16:1 is considered as maximum fuel economy ratio."


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## GTI's (Nov 27, 2011)

rdy105 said:


> SOLVED: I replaced the fuel injectors and it runs perfectly. No codes, no hesitation, no misfires!


Glad that you figured it out.


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## le0n (Jun 12, 2013)

cool.


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