p0300 code on 2004 4.4
 

Ok, so i have a dilema, i have a 2004 4.4 x5 with 137k kms on it. Recently i moved to Toronto, ON from Edmonton, AB and drove the whole way here, during the drive everything was fine, smooth as can be for the whole 3600 km trip. About a week or so after getting to Toronto i started having problems with a mis-fire (code p0300).. now i know that this code means multiple cylinder random misfire, so first thing that came to mind was spark plugs because they had never been changed before.

So i replaced all 8 spark plugs with NGK part number BKR6EQUP which i got from the parts department form a bmw dealer, during the replacement of the spark plugs i noticed the dreaded oil pooling around the spark plugs and knew it was time to do the VCG's. So after cleaning up the oil and putting the new plugs in, the car ran fine...for about 5 minutes.. then the engine light would start flashing again with the same code, so i thought the code comes back because the oil starts pooling around the spark plugs and the end of coils causing a short.

Fast forward to last monday, the x5s out of the shop with new VCG's and all the coils tested fine so i thought everything was fixed, turns out i was wrong and the code is back again and the engine is shaking..

Anyone ever deal with something like this? i feel like i hit a brick wall...

Again the parts that have been replaced/tested;

Spark Plus
Coils (tested)
CCV's
Valve Cover Gaskets

Engine is shaking because the DME is shutting down the cylinder(s) with the misfire. Something else is causing the multiple misfires other then spark plugs and coils.

Misfire could be a lean condition where the cylinder that is running lean does not produce the same amount of power as a good cylinder. You may not be able to detect this difference but the computer can. What are the short term and long term fuel trims. The computer will add fuel to a lean conditiion and take away fuel from a rich condition.

You need to look at real time data in order to fix this problem.

Could also be the rubber ccv diaphragms at the back of the head.

Check also your Cam sensor position - mine was leaking, creating misfire and code with ses light.....ps there is 4 sensor

UPDATE:
So I fixed the issue, it turned out to be a leaking intake manifold gasket. Replaced the gaskets and all is well, I guess you can call it a vacuum leak as the car was "sucking" in more air then what the MAF was registering thus meaning the computer would either cut fuel or spark to the cylinder(s) that were getting extra oxygen (atleast that's what I think I could be wrong as far as the cutting fuel or spark).

Just had 1 more question, what are the chances of all 4 oxygen sensors going bad at my milage (137 K kms or about 85k miles)?

I'm not 100% sure about the four oxygen sensors yet as I have yet to pull the codes myself and I'm just going by what my indy is telling me.

You could replace the pre cat O2 sensors as preventative maintenance as their primary function contributes to fuel/air ratio. Post cat sensors contribute somewhat to fuel/air ratio but primarily monitor emissions. You are in the range where pre cat sensors can fail. Post cat sensors usually last over 100,000 miles.

I agree you should check for codes. If the pre cat sensors are acting up you may see other related codes, like a lean cylinder(s), rather than an O2 codes.

I am all about performance so I replace O2 sensors before there are symptoms or codes. On my wife's care I still replace them in pairs but not until there are symptoms. The first is the school of thought--that if it's not broken it soon will. The second is if it isn't broken don't fix it. Either route is a reasonable course of action as it relates to O2 sensors.

In my case i was talking about the Cam sensor position (2) and exhaust sensor (2) the two Cam was shot on mine after only 110kil ...even my INDY was surprise to see them finish...absolutly need OEM (don't go cheap eBay) those are not free (like $100cdn each) there are so many sensors on the 4.4 it's crazy here is a link explaning those sensors (cam) if your are ok just leave it asis.....Camshaft Position Sensor Failure Symptoms

About the same chances as winning the Powerball Lottery.

Ugh.... Seems I spoke too soon the p0300 code is back along with the p code for the bank 1 sensor 1 o2 sensor, I assume that is the pre cat o2 on the passenger side of the engine (LHD) correct me if I'm wrong. I'm really really hoping that this fixes my issues as the pre cat o2 sensors deal with the air/fuel mixture. I'm going to order the OE Bosch sensor probably tmr. If that doesn't fix the misfire I guess I'm off to the dealer for a diagnostic. Idk if I should fork over the $$$ for the 4 cam sensors just yet with out getting a proper diagnostic on the truck....

Either way, any input is appreciated greatly.

If you going to work on your car, you need to get a scanner that can provide real time data. I use the app TORQUE on my android cell phone and tablet. It can provide short term and long term fuel data.

Since you got a DTC for an 02 sensor I would check to see if the sensor is faulty. There are many youtube videos on checking 02 sensor. I suggest you review some of them.