Misfire on all cylinders on one side

[mrathell]

Originally Posted by Skyline

What was the condition of the plugs you pulled from the low compression cylinders? Were they black and oil fouled or were they nice even grey?

I installed new plugs and after about 2 weeks of driving I pulled them and they were completely black on all 4 prongs, dry with no oil residue,

Originally Posted by Skyline

Did you try swapping the coil packs on the left bank with the coil packs on the right bank to see if the problem moved?

Yes, I swapped all coils from one side to the other with the same result staying on the driver side. I even pulled each plug to make sure it would fire when the ignition was turned on and they all did.

[mrathell]

Thanks guys, but what kind of issue can exist in this type of scenario?

It seems as all scenarios mentioned would result in oil burning, except for the "ground" reason suggested. I have to research on how to test for a bad ground on the ignition wiring. It would have to be a ground that is connected to all 4 cylinders while not connected to the passenger side bank.

What would cause misfire at idle but doesn't when RPM's are over 800?
What type of issue can go away by increasing RPM's?
What type of issue can exist in the above two questions while not burning oil?

[SlickGT1]

The problem is that he is not adding any oil.

So if he is burning it, how is his level still fine. The plugs do display signs of oil though. But he had leaky VC gaskets, so that is really a moot point. He should be blowing a puff of smoke at startup.

Right, we are hoping he did the leakdown correctly, all in TDC.

Get another mech to take a look at the engine. Something is not adding up.

[mrathell]

Yeah it looks more and more like its time to throw in the towel because I don't want to invest more money into a car that may or may not run properly.

I don't mind doing the work myself but a mechanic is only going to charge me a ton of money for research and may end up with the same results.

Not in a million years am I thinking I know even a tenth of what you guys know but it seems to me that:

- bottom end piston rings would result in burning oil: not happening

- bad valve seals could mean low compression without burning oil BUT the low compression would continue even when I accelerate. Going up hills or anything that required more torque would cause for me to bog out due to low compression: not happening

- if it has low compression, wouldn't it run worse under load? The engine requires more horsepower unload right? So wouldn't the performance get worse while driving because of the compression issue?

Lord knows I could of made many mistakes in my testing, so even if we go with the notion that my data is flawed do to user error, I think certain things should be ruled out due to the facts of how the car is behaving now and only focus on the things that could result with my profile:

Facts:
- The car isn't burning oil
- the oil and antifreeze is NOT mixing
- the misfire on all driver side cylinders go away when rpm's are over 800
- the only codes being returned are for misfire
- the misfire codes go away while driving

To me it seems the direction should be: What would allow for the cylinders to get compression at 800 rpm's but not at 600 rpm's while idle?


Sorry guys, just a little frustrated after tearing down this engine and still clueless.

[Skyline]

Try cleaning every ground point you can find on the engine.

[mrathell]

Originally Posted by Skyline

Try cleaning every ground point you can find on the engine.

OK, call me hardheaded.

Today I unplugged all of the ignition coil wires from the driver side while the car was running and the backfiring stopped (as expected).

I then plugged each one back in until the backfiring started again. The backfiring would only happen when I plugged the #6 cylinder back in.

So at this point I noticed that the ground wire from the head and the ground wire from the #7 ignition coil were connected to the screw post for the #6 ignition coil. Now I'm thinking about what Skyline suggested.

So I took both ground wires off of #6 and connect them to #7.

I started the car up and its still missing but it doesn't backfire anymore and I'm only pulling one code now......P0306 (misfire on #6). The X5 is running better than anytime I've owned it.

The check engine light sometimes even goes off for a few minutes.

Whats funny is that when I first got the X5, the only misfire code I was getting was for #6, but after I changed the water pump and the ignition coil for #6, I started getting misfires codes on all driver side cylinders.

So after all of that I seem to be back to absolute square one. But this time I feel there is a glimmer of hope.

Now I need to determine the true cause of the misfire on #6.

[SlickGT1]

It's a bit mind boggling.

Shot in the dark. Might be an avenue worth looking into. Check the vacuum pump. Is there a vac pump on these 4.4s.

Ground is also something to check.

[mrathell]

There are four heavy gauged rubber coated wires that bolt to the heads. Two on each head. They are bolted directly To each head under the intake manifold. They are visible in the photos on #63 of this thread.

Can anyone confirm if those are grounds.

[TwinTurboGTR]

Those are the knock sensors.

[bastereo]

Guys, rabbit trails!

He has low compression on 4 cylinder and misfires on those cylinders. That is the problem, end of story.

While it is unlikely that his rings are bad without burning any oil, its not impossible. There are 3 rings on each piston. 2 compression rings and 1 oil ring. I bet they all have specific purposes...

I had a much longer response typed into my phone, but it didn't post...

Short story, I have seen the leakage causing misfire at idle before, both times were valves, but they only missed at idle and acted fine off idle.
At idle everything moves slower and there is more time for the compression (air/fuel mix) to leak out, once the engine is spinning faster there is more air and fuel in there (the throttle is open) and with everything moving faster the time it can leak out is smaller so the leakage is a smaller percentage.

How the previous owner managed to kill the compression rings on one side, that's crazy...