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P0306

8K views 12 replies 6 participants last post by  Patch's 
#1 ·
Hi guys have been trouble shooting some codes but this one has me puzzled!
brand new coils, wires and plugs no junk:
P0306 Cylinder 6 Misfire Detected

Conditions For Setting This Code:
* Coil Voltage 200 - 350V
* Secondary Voltage 8 - 20V
 
#3 ·
"Did you check the gap on the new plugs? I know most OE plugs say are pre-gapped but it never hurts to check that. It's also possible you just got a bad plug but at least you have narrowed it down the affected cylinder."

Yes I always check especially when you consider the pain they are to do.
Remember you have 2 firing at the same time for each cylinder below 27?? rpm chances of both new failing is not likely.
There has to be a cause effecting these new parts either before, after or during there cycle. I have an idea but would like some input before I start taking things apart.
 
#4 ·
The plugs actually *do not* fire at the same time, but rather sequentially. You probably noticed the "a" and "b" labels on the coils, they match up to the A and B plugs (marked in the heads or head covers, can't remember at the moment). If you didn't notice that when you were replacing the wires, you want to check to be sure you have them matched up, A to a and B to b.

Since you replaced all of the ignition components, that only leaves four possibilities. Compression, bad valve, vacuum leak or fuel injector. There are connector kits for the fuel injectors, so I'd probably start there, or of course you can stick a compression tester in there. And you can of course swap a fuel injector to see if the miss moves.

The caveat to all of that is that you'll need to do a compression check on the entire engine so you have a baseline. And the miss may actually not be on cylinder 6; I had a pending miss code on my car for No. 3 and it turned out to be a bad wire on No. 4.

There is a vacuum connection right at the back of the manifold on the right for the brake booster, which might overly affect No. 6 if it were leaking, so that might be something relatively simple and quick to check.

Good luck.
 
#6 ·
If I was the one swapping, I would probably rather do it between 4 and 6 for the simple reason that 6 is a pain in the ar$e to get to, while 4 is the easiest.
 
#7 ·
Well some good ideas and I will be performing the compression test but not for the cause I started the thread on.
I have to disagree about the sequential firing though I am certain about that but will look it up encase I am getting my engines mixed up, I have mentioned this before as the sequence changes with rpm do to filling challenges and getting the most out of the advance burn at higher rpm.
I have not been able to locate any vacuum leaks and have check it many different ways as well as replace all the gaskets at the manifold and checked every line forward of the firewall with a vacuum pump, if there is a vacuum leak I can't find it nor would it explain:
Conditions For Setting This Code:
* Coil Voltage 200 - 350V
* Secondary Voltage 8 - 20V
it very specific
 
#8 ·
Maybe this will change your mind about the spark sequence. :D
 
#10 ·
I had some time to work on the MB this afternoon and solved the problem, as far as I know there are only 2 causes and the plugs being new it had to be the injector her is what I found, how I repaired it was simply repeating the cleaning steps for the # 6 injector which is out of order in the pictures but made it easier to access and photo, the other 5 cleaned and flowed well after typical efforts.
58psi
took it for a spin and what can I say about these cars is when tuned they are a real pleasure to to drive, next time I pull those injectors I will likely replace them with the \bosh gen3.
Patch
 

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#13 ·
1st I wouldn't recommend cleaning your own injectors if you are not experienced knowing what to look for, it can be a real waste of time and things can go from bad to worse easily.
I have a sonic parts bath I cleaned then changed the fluid to a 50/50 mix of Simple Green
heated to 150f +/- brushed them with a tooth brush and soapy water rinsed them making sure to move the dirt on the surface away from the injector. Then I measured resistance cold then warm 15.6 &16.1 ohm, I hooked up a micro switch to 12V and soaked them one at a time giving them many short burst to cycle the fluid through the injector. I then check them for resistance again and pumped some Lucos cleaner through them with a small shop pump while pulsing the micro switch then installed them on the rail using the clips to hold them I would operate the fuel pump monitoring them for leaks I placed a drop of soap on each tip which showed the air bubbles. I have seen different guys do it different ways the idea is to have a sound injector not one that merely passes fluid, so the quick stuff you see or hear is not going to cut mustard when it's back in the chamber, there are a host of codes and issues caused by leaking injectors.
#6 needed 2 more tries to get it to work properly but because I flipped the rail and made sure when done the pattern and leaks were taken care of it worked out!
Here is a reputable place for rebuilt injector Jon over at injectorconection.com your sure to get a popper working & matched set of injectors at a reasonable price!
Of course if I had a flow bench that would of made for an easy job, but as it's just a hobby...
You can get the filters and o-rings in the form of and injector kit on ebay.
 
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