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P0303 2005 325xi with Pictures

2K views 12 replies 2 participants last post by  diceman0925 
#1 ·
Have the dreaded p0303 code.
Replaced coils, plugs, air filter, maf switch, checked hoses, vacuums, etc.

Rechecked the plugs and the 3rd cylinder plug is clean, as in , not firing.
the others, all newly replaced, show firing evidence. When i took a pic of the cylinder after plug was removed, it appears wet.

See the pics.

Car has 166k miles and is in great shape...what do you think? Engine job?? Worth saving? Do i bring it in to dealer to have them look at it?

Engine compressoin is about 155.
The 3 cyinder about 30 less.

The pics show a normal plug and the clean nbr 3 plug.
The shot is looking down to the piston, which is wet...
 

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#2 · (Edited)
Usually wetness in the plug well is from a leaking valve cover gasket. It's a 3 piece gasket - one big rectangular gasket around the edge of the engine, and then two three-ringed pieces that fit over the 6 spark plug wells. It can short the plug and prevent spark.

Either that or you didn't get the plug tight and you're getting vapor from the cylinder, but you probably got it in there good and this is just oil. Although.... with compression down in that cylinder it could be a leaky thread I suppose. I think that can be fixed for relatively cheap but not sure. Maybe one of those things that is used when threads are stripped/crossed - "helicoil?" :dunno:

Clean up the well and the threads and coil really well and try it again. It'll probably fire until the oil returns and repeats the fail cycle.
 
#4 ·
Not sure this is explaining why oil is coming UP from the bottom of the spark plug well.
We're going to clean and restart it to see if oil continues to come up from the bottom.

If that is the case, is this a problem with the rings or something other?

I dont think we have a thread problem because it's in there nice and tight with a new plug.

Something is causing a compression issue and I'm hoping it not a huge $$ repair bill.
It would be a shame to give up on this car.

Thanks again,
Dave
 
#5 ·
I think it could cause a misfire. The plug would short before it sparks.

I don't think rings would cause this leak. Lower compression, sure. But the only place it can leak from at the bottom if the plug well is the threads and crush washer on the plugs. Unless the head is cracked by the plug hole.


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#6 ·
ok, here is where we're at.
We cleaned out the plug shaft and cleaned the plug and cleared the codes.
Car ran well idle for about a minute, then we stepped on gas and it began to misfire along with service engine light (p0303) code.

Removed the plug and the threads of the plug are coated with oil.

The rest of the plug is clean and looks news.

Wondering if there is a root cause on why it would idle ok and then fail within a minute?
O-rings? Valve Guides? Do I need a new engine?

Dave
 
#7 ·
For the first minute or so it runs on a basic, slightly rich fuel map to keep the car running until the pressures build up and the idle can settle in. Then it starts taking inputs from sensors and adjusting as needed.

No other plugs are showing oil?
 
#9 · (Edited)
Your old stuff is showing definite signs of leaking valve cover gasket. Sometimes it's hard to see where the leak originates but the oil will pool around the plugs and stain the coils in the way down.

Also, the black oiliness in the tips and threads of plugs indicates a clogged CCV that is passing heavy oil vapor into the cylinders. Frequently the clogged CCV will accelerate Vcg failure.

I would pull the coil and new plug on 3, and put the old plug into the hole. Then you can hold the tip of the coil/new plug against the head to ground the tip and start the car. Will tell you if sparking ok. Also check condition of 3 injector. Might be gunked up n not spraying well and that's causing misfire w fuel cutoff. Soak the tip in injector cleaner.


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#11 ·
Well for a proper firing you need a fairly precise mix of fuel, air and spark. So if one or more of those ingredients is out of proportion, yes you'd get a misfire. Nothing is really pointing to air so fuel and spark are what to chase at this point. With a new plug n coil I'd say spark is probably ok. But with the oil presence hard to say. Might not be grounding enough to spark. Really looks like the plugs not firing tho. But if there's no fuel in there it could be firing and just not getting schmutzed from the combustion.


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#12 ·
I agree with you, but there is something that is limiting the problem to cylinder 3.
So maybe a bad fuel injector, or a bad valve cover gasket specific to cylinder 3.

The CSV would affect all valves, I would think, and that's probably why all are exhibiting some oil stain. The p0303 code though is what I'm trouble shooting and focusing on, so I think right now, I'm at the point where I go to BMW pay their blood money for an analysis to make sure I'm not missing anything and work off their recommended to-do list.

If they can't pinpoint it, there's no sense in have them replace part after part until this is resolved.

Appreciate the comments....I'll be sure to post on whatever develops.

Dave
 
#13 ·
Problem Solved

Went to BMW for the $147 analysis and check and they road tested the car but failed to find a cylinder misfire code and instead got lean fuel mixture code, possible O2 sensor.

I told them I was getting P0303, so they began swapping out the coils one by one and found that one of my recently replaced coils was different from the 5 others. They showed an issue with Cylinder 1. So they swapped in a new coil, road tested it and the engine ran smoothly with no issues.

I then told them I had low compression in cylinder 3, about 20psi lower than the rest.

I had them do a smoke test and they found a torn intake boot.
I had them replace that and re-smoke for any other issues and none found.

Thankfully, I did not need engine work, although all said and told, I put $2400 into the car.
However, I did replace a lot of parts, plugs, coils, filters, sensors and fixed an antifreeze leak, too, so for now, the car rides extremely well and these parts have been updated, which needed to be done since the car has 165k miles!

Thanks for your input and help along the way.
 
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