My Wife’s X5’s Problems…

My wife’s 2001 X5 3.0i with 100k on it is being very difficult. A few months ago, her X5 started giving us problems. It was the cam position sensors and it worked well for a month or so. Then, about a three months ago, her car just died on her on the way to the store. The fuel pressure was low, and I replaced the fuel filter and the fuel pump. Problem appeared solved. She put about 600 miles on it over the next few weeks with no problems.

Then a month later , it died on her, again. I replaced the spark plugs and cylinder #1 coil. Started up, idled, but then on it’s test drive around the block, once the engine reached its normal operating temperature, it died on me. Pushed it home, and read the codes again. This time, it gave the following codes (from the Peak R5/FCX-3):

19: Table
EE: Misfire Cylinder #1
EF: Misfire Cylinder #2
E3: O2 Sensor Adaption Limit, Cylinder #1-3
E4: O2 Sensor Adaption Limit, Cylinder #4-6
19: PreCat O2 Sensor Heater Insufficient, Cylinder #1-3

I changed the pre-cat O2 sensors. It started, idled, but I didn’t drive it this time (spent the weekend moving too). After it reached its operating temperature, it stumbled, and died. It gave me the following codes:

19: Table
EE: Misfire Cylinder #1
EF: Misfire Cylinder #2
E3: O2 Sensor Adaption Limit, Cylinder #1-3
E4: O2 Sensor Adaption Limit, Cylinder #4-6

What was I missing? What else could I test/check? I was stumped. I reset the codes with the Peak Scanner, but they still come back after it dies. Unfortunately, the codes do not show up on any other scanner, just the Peak one.

I then checked the fuel pump relay. I wasn’t getting any pressure after the car died. I checked the pressure gauge and it said 20 psi. I tried starting it again, and it went to 10 psi. I couldn’t hear the pump running when I turned the key (key on engine off).

I unplugged the MAF to see if it would start. No change. I looked around for cracks in the intake tube, but did not find anything. I jumped across the Fuel Pump Relay to see if it would start. The pump did run, but whined very loudly. It would crank, but not start.

I checked the fuel pressure, and it said 15 psi. Way too low. I then went down to the gas station, and got 5 gallons of gas to see if maybe the fuel level sensors were faulty. Put 5 gallons in, and ran a jumper for the fuel relay. The pressure went right to 50 psi.

I put the relay back in and started the car and it was at 50 psi. I let the car idle for a while, letting it reach it’s operating temperature. As the engine temperature rose, the fuel pressure started dropping and I could hear the car start to stumble, then shake a little. It would level out, but as the car’s engine temperature rose, the car started idling rougher and eventually the fuel pressure returned to the 20 psi and the car died. It will crank, but not start now and the pressure is at 15-20 psi.

I recently replaced the fuel pump and filter/regulator, so I’m hesitant to think it was the fuel pump, filter or regulator.

As an aside, I’m sick of everyone saying my fuel pump is bad because they saw it on the news.

I took the pump out today and looked in the tank. To my surprise, the fuel pump side was bone dry, however, the driver side with the second fuel level sender was filled to the top of its cavity. This should not be, as I added 5 gallons last night.

With this information, I added 15 gallons of gas, pretty much filling the tank. I reinstalled the fuel pump, ran the jumper first. It came up with 51 psi. I then put the relay back in, and started the car. It came up with 52 psi (which is actually 6 higher than the high end of the pressure spec in the Bentley book (46 psi)). I let the car idle and reach the operating temperature. It never stumbled or died and stayed at 52 psi. I think there is a problem with the suction pump that transfers fuel from one side of the tank to the other. Now, I do not yet know if it is because there is a kink or blockage in the line or a failed suction pump. I’m leaning towards that later, as the fuel filter/regulator are new and my wife was able to drive for a few weeks with it and run it down to an 1/8th of a tank multiple times.

After replacing the transfer pump, I figured the problem was fixed. However, the fuel pressure did not drop to the specified 46 psi. This made me nervous, which was proven to be an appropriate response. Her car died on her on her way to the gym. This leads me back to the fuel pressure regulator or a vacuum line problem. I went online and ordered the vacuum lines from ECS tuning.

I replaced the vacuum lines, but that still did not do it. After discussing the issue with my local indy mechanic, he mentioned that it could be a simple o-ring that goes with the transfer pump. I ordered the o-ring, and replaced it. Finally, the issue appears to be solved!

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About spngr311

Photography. Cars. Surfing. My life.
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