2000 Ford Taurus wagon, **FLEX FUEL** V-6 engine running on regular E10. Began stalling intermittently. Would run rough for 30-60 seconds or so and then die, both while driving and while idling. Would restart just fine. Began happening more and more frequently and threw a Check Engine code (but I don't know what it was, repair shop says they “lost it”.) Then one morning it wouldn't start (mild Oregon climate ~55F overnight). Had it towed to an independent repair shop. They read the code and measured fuel pressure at the fuel pressure test port (on the very far end of the fuel injection rail from the gas tank) at 3psi. They diagnosed a bad fuel pump and replaced. Told me it was ready to pick up. It had been sitting out overnight. When I picked it up, it wouldn't start. With lots of cranking it finally started but ran extremely rich. Strong smell of raw gas out the exhaust and clouds of fumes (not burned oil, just unburned, rich exhaust). Gave it back to the shop. They read code P0191 and diagnosed a bad fuel flow sensor (device right at the beginning of the fuel injection rail) and replaced, but it didn't affect the problem. It will still sometimes have trouble starting and run very rich when starting from cold (cold = 55F). Without touching the throttle, engine can be shut off and started again and it will be just fine. Shop doesn't know how to proceed. I walked through with them their diagnosis of the bad flow sensor. Upstream of the flow sensor is an oval-shaped metal enclosure with fuel lines going in and out, and an electrical connection. They didn't know what this device does (neither do I). I suspect it might be the electronic fuel pressure regulator.
It is unlikely that there would be two bad components at the same time in the fuel delivery system. I suspect that the bad fuel pump was a misdiagnosis, and the bad flow sensor is obviously a bad diagnosis. There are two TSBs that might be pertinent – TSB14187 & TSB14041. But I don't understand completely the flex fuel system. What controls the fuel pressure to the fuel injection rail? What device senses the ethanol concentration of the fuel system? What is that oval box in the fuel line? What does the engine change in response to the ethanol concentration? What could be the true problem here that would fix the car?
Tuesday, October 30th, 2012 AT 6:31 AM