I did some more work on the x5 to try and resolve the multiple misfire codes from only one side of the engine. Below I have listed what I did today and the previous days. If anyone has any clues please chime in:




I changed the water pump.

It was originally throwing the codes P1421, P0300 & P0306

So I changed all of the spark plugs and the iginition coil for cylinder #6. The old spark plus had carbon build-up but nothing bad and no signs of oil on them.

I cleared the codes and now I'm getting P0300, P0305, P0306, P0307 & P0308.

The X5 still idles rough, but once I put in in drive and start driving, it drives like a dream until you stop at a light and it rough idles again. It's not about to shut off but a rough idle.

When the car is cold, there is a loud ping/clank sound coming from the left rear of the engine. almost as though you are hitting a wrench against metal. It happens once every 10 to 15 seconds and then goes away after the engine warms up.

The next day I did the following:

1st) I took out the O2 sensor (before the catalytic convertor) and drove it without the O2 sensor to see if the catalytic convertor was bad. The X5 was still running rough and throwing the same codes. This must mean the catalytic convertor is working. if the rough idling issue had stopped, that would of meant the catalytic convertor was clogged and bad.

2nd) after putting the O2 sensor back in, I started the X5 and while it was running I removed the plug from each ignition coil (one at a time), to see if the idling of the engine would change. The engine idle didn't change. I believe the idle should of changed if the ignition coils were firing. So that must mean the coils are not firing as the codes suggest.

Today I removed each ignition coil (one at a time) and the corresponding spark plug, keeping the ignition coil connected to the power plug and had the spark plug connected to it as well. I then had my son turn the ignition on as I held the threading part of the spark plug next to a good ground (-) on the car with the expected results being my ability to see the spark generate on the spark plug. If I didnt see a spark, that would mean there is no fire going to the spark plug, which MAY mean the iginition coil isn't working. But I saw blue sparks on all spark plugs. Still pulling the same codes plus now the maf sensor code.

I cleaned my mass air flow sensor with the maf sensor cleaning spray, now my maf sensor doesn't work, so I had to order a new one. Now the car shuts off right after starting it but if I unplug the maf sensor, it keeps running.

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2000 X5 4.4i w/ 150K miles.