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fault codes p0304 p0305 p0306

marcone

Member
Joined
30 May 2017
Messages
10
Hi everyone, I am in need of some assistance please. I have the above codes with poor running on bank 2.
The coil packs and plugs have been changed over form bank 1 and still the same.
The car is over fuelling with rough running on bank 2 at about 20% with the opposite bank at -20%.

The timing check specified and actual are as close to spot on.
Any help would be much appreciated.


Marc
 
If you have an entire bank running rough then you need to be looking at things that are common to that bank. Typically these will be:
1. A vacuum leak - unlikely if you haven't been rooting around the piping/ducting on the top of the engine though.
2. A duff lamda sensor. These may not throw up errors themselves but their failure can be evidenced by comparing their live voltage readings from bank to bank. There is a range they are supposed to fluctuate within and if they are outside that range then they're duff. TBH though, you can get a genuine Bosch lamda from ebay for about £55 so I would try this first.
3. The variocam actuator could be duff on that bank. It's a pig to fix because you have to take the cam cover off. It normally has it's own code when it fails though. If you go down this particular rabbit hole, double check the electrical connections & earth to it first.

My money is on your issue being down to a duff lamda sensor though. That's where I would start.
 
Thankyou for replying. I do have hardly any activity on that bank pre cat and the other bank is switching nicely. I have one coming to me but wasn't sure that it wasn't the engine not allowing the lambda to switch as it is overfuelling on he rough running bank.
I have performed a variocam actuation when running and both banks are switching on and off with a prominent change of engine tone.
I will report back after lambda change.
 
If the lamda isn't switching as it should and the fuel is over-rich, then the car is running that bank in open-loop mode and over-fuelling to keep it safe from detonantion because it doesn't trust the O2 reading from the lamda. Once you replace the lamda it will go back to closed loop and the fuelling will return to normal.
 
Hi I have installed the lambda and still getting codes as above. It the lambda switches better and does not smell off neat fuel.
I got the full story about this car from the owner today and the engine has been out for head gaskets.
My first thought was timing but I have checked on durametric and the specified and actual are spot on.
I am wondering if it could be a adaption issue as it has been out but I cannot find any adaption section in durametric to rset the vehicle.

What does everyone think.
 
Do you have access to some sort of diagnostic tool that will give you live data?
 
Is it a two or four lamda car? Also are you cancelling the codes and they're coming back, or are you waiting for them to go away by themselves?

When I had a lamda go bad recently it took several drives and cancelling the codes before they stayed away.
 
Hi can here that it isn't running correctly on 6 so a drive it is definitely not ready for.

We have pulled the engine out now so to double check the timing on exhaust side, which is spot on.
I have found a poor earth for the coil packs so we are just renewing it now.

I am trying to check as much as possible before refitting engine, when it was running the misfire counter on bank 2 was going crazy counting up at a tremendous rate.

I am trying to find if there are any adaptions needed if the car has had the battery disconnected for a long period as this obviousl has witht he engine out.
 
When you clear a fault code from the dme on these it resets the adaption values .. if you dont have a fault code and want to reset adaptions then you just pull off the maf sensor plug for a fews seconds .. that will generate a code you can clear and so reset adaptions .

Need to start with basics really .. you have a single bank misfireing .. noid light in each injector .. is it switching .. pull a coil pack .. jam a plug in it and earth it .. does it spark .. do the same for each cyl ..

You now know if you have spark and fuel .. then move onto timeing .. cam timeing here .. does the tool fit correctly at tdc on each bank .

Fuel pressure is unlikely but you still check it to eliminate it.

Maf check .. pretty unlikely but unplug it and run .

Changeing a lambda sensor and clearing a code should have stopped it if it was that .

Vario cam is tested with drive links on a tester .. does this car have x2 cam sensors .. have you checked the values for them .

Have you done a compression check

just some basic idears .
 
Hi I have done a compression test and it is 180psi each cylinder on bank 2 which is the faulty bank.
I can check cam timing on the durametric and both banks are running spot on with specified and actual so in my mind the cam sensors are picking up and cams are in sync.
I have done valve lift actuations while running and they switch and you can hear the note of the engine change though the inlet so I would like to say they are functioning correctly but don't know if I can rule out variocam issues

When it is running and I hold the revs above 1000rpm it is popping and banging back through the exhaust which would indicate a timing issue but it is spot on but the misfire counter is going through the roof.

I will pull the coils and check for firing but when I pull the plugs they are black but not wet so I would say they are firing but possibly not at the correct time.
 
Are there any fault codes logged ?

Do a physical check on the spark .. a weak spark due to a poor feed / earth will cause this .. pretty rare but possible . same on injectors a poor feed / earth will cause poor injection.

Knock sensor for that bank will retard the ignition timing .

Are the injectors leaking , never seen 3 but i have seen 2 .. injector swop or rig up some sort of system to look at them out of the car .

I would also be looking at the cat ( melted ) .. if exhaust gasses cant get out then it will run rough .. perhaps remove the lambda sensor and run it to prove .

A lambda sensor can be unplugged , the car will run on defaults of what it sees from other sensors and obviously ignore that sensor .

Bear in mind .. we eliminate the obvious and what ever is left no matter how incredible is the answer and we are working back to it being the dme by testing everything else .. which other than a swop cant be tested .
 
I will do some more checks tomorrow. I have pulled the engine today repaired some earths(which I thought was the issue) and reinstalled the engine but still the same.

Now I still have rear boxes off so I can feel we have pressure coming out both cats so seems not to be blocked.

Now when running bank2 cat is getting hotter than bank 1 cat and bank 1 is running correctly which is weird.
I will start again tomorrow.
 
The fluctuating lamda values from earlier on in the story that have now (I think) been resloved may mean that the over-fuelling that heppened before this was fixed fouled the plugs.

It may be worth trying new plugs in bank 2 to resolve.

Thinking about it further, the last time I had this kind of popping and banging was when I had an AOS vacuum hose loose. The extra air would explain the poor running and the lean (hot) running. It might be time to pull and re-seat all the air hoses you can find.
 
Hi I have run alot more checks today, totally went back to beginning.
Fuel pressure 60 psi running
Coils pins 1+15 2-3ohms
All injectors pulsing with noid light( cannot tell you pulsewidth at the moment.
Timing spot on with 1-3 degree deviation on running with actual and specified spot on.
Swapped vario can and valve lift solenoid and still the same
Swapped cam sensors
smoke test through inlet and no leaks.
Coils sparking both banks but cannot be sure if bank1 is sparking brighter and bluer than bank2.
I need to scope out injectors and coils to see what the comparison is.

Another compression test on all cylinders bank1 230 and bank 2 245-250.

bank 2 stinks of fuel while doing a compression test it is almost like a command for extra fuel but everything in live data is good.

God this car is stressing me out I keep thinking weak spark or overfuel as plugs are so black or am I missing something. If it was timing or variocam it would show on live data and possibly fault codes.
 

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