Subaru Outback Forums banner

2003 H6 - P0301 - P0306 Codes in Vanagon

12K views 71 replies 9 participants last post by  Rjhdog 
#1 ·
Hey Friends,

I recently threw P0301 - P0306 codes a couple weeks ago in my 2003 H6 3.0 in a VW Vanagon. Before all go running away as they are not familar with the conversion, I ask you to help with any thoughts as you know the Engine more than most. I would love any insight you can offer even if you are not so comfortable!

I had the same codes a few weeks back. I cleared them and all codes came back a second time.

I am hoping the Misfire on all cylinders could be related to my intermittent idle issue as seen in my past thread:

http://www.subaruoutback.org/forums/66-problems-maintenance/107633-2003-3-0-idle-issue.html

Car drives fine - nothing noticeable - same gas mileage, same driving characteristics, etc.

I would be elated if these codes are actually related to the idle issue as the old issue never threw a code. Perhaps this will help narrow it down.

What do you recommend to begin the troubleshoot?

Thanks!
 
See less See more
#2 ·
did you try swapping the coils around and seeing if the mis-fire moves to the other cylinders. ?

(of course getting them all to audibly "click" into place).

coils last a long long long time,...rarely given trouble on these engines,...but I guess one can bump them when the engine goes in and out of a bay, be it a subaru or a cool old chick magnet vanagon.
 
#3 ·
With all 6 cylinders reporting a misfire I'd start by reading the fuel trims from the ECU with an OBDII scan tool- hopefully you've still got a connector for one dangling somewhere under the back seat.

I'd guess that the engine is either measuring air incorrectly (actual air leak or general electrical problem causing faulty measurement) or you've got a fuel pressure problem causing lean-out.
 
#4 ·
could you confirm that you got mis-fires on ALL 6,...or just #1 and #6. ?

(hard to tell what exactly the " - " means in your first post)
 
#9 ·
I use Premium fuel always.

I can't remember the exact spark plugs I used but they were around $12-14 each. I believe I researched the ones that are best for the H6 and purchased those. I installed them some 30k miles ago.

Any other thoughts?
 
#11 ·
if they were copper plugs, they may be getting old. If they were platinum or iridium, they should be OK. But, not knowing if they were NGK or some other brand, we can't be sure about them.

as mentioned, some info from the sensors via live data or even FreezeFrame data would help.
 
#13 ·
no oil in tubes means no chance it's causing misfires by shorting the high voltage, sounds like the plugs are all fine too. So, it eliminates those items.

kinda puts it back to air, fuel or "electronics". I have had spurious codes set by a bad battery - maybe confirm voltage in charging circuit and no bad cells in the battery.

vacuum gauge might help find a vacuum leak.

some of the above might show-up in fuel trim numbers.

has this happened in more than one tank of fuel? maybe bad gas?
 
#15 ·
Many thanks for the advice and wisdom here.

I gathered some live scan data: I will post some photos in the following posts. Any advice or insight will be most appreciated. I gathered info from a fancy snap on guage as well as an older gov smog sniffer.

Long story short, the mechanic thinks I have a vacuum leak due to hydrocarbon numbers and the Ecu is running fuel on rich side to compensate.
He is not a Subaru expert so I would love some other opinions given the data.


Also, I am wondering is the Idle air control valve is functioning properly given a min 13- 14 Max ???

I would love to address my idle issue ( link from the original post) as well if possible.


Many thanks all.
 
#29 ·
hope cdc will educate us here. good job with all the data.

fuel trims look good except in that last pic to my untrained eye - I want to know if a MAP of 10 is normal, and if the advance of 10 degs. at idle looks normal

why is the ecu pulling fuel in that last run?
 
#31 ·
Hey Texan.

What do you think about the possibility of a vacuum leak due to hydrocarbon readings? He believes it's running on the rich side to compensate.

Is MAP directly related to the idle air control valve? Is the 13-14 range found on one of the images of idle air within normal conditions?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top