It had an intermittent misfire when she bought it four years ago, but the misfire would go away. It started to happen only when it was really cold and humid, and when we moved back to Texas, that meant we got the intermittent misfire once a year. So, nothing to worry about.
Couple weeks before Christmas, the misfire came back and stayed. Thinking it was still going to be intermittent, I didn't worry about it. On a whim right before new years, I went ahead and did the coil pack (96 ford taurus, v6, one coil pack for every cylinder, but no distributor). Because, you know, I'd already diagnosed the intermittent misfire as being a coil pack going out, so when the misfire became permanent, I replaced the Known Bad Part first.
That didn't fix it.
So I figured the spark plugs that were misfiring probably got fuel-fouled, or oil-fouled, or both. Not in a hurry to pull the plugs (the three on bank one are a PITA, being near the firewall and all), I threw a $4 bottle of fuel injector cleaner (aka snake oil) at it to see if it would clean up the spark plugs. A few miles later, it got worse.
Then the cat caught on fire.
I got the fire out without any real damage, at least not visible damage. Right before the cat caught on fire, the car started backfiring and lost all power. So now it's accelerating like grandma. Obviously the cat caught on fire because it overheated with all this unburnt gas being blown into it. I hollowed out the cat after that, so it won't catch fire again.The fire took out the O2 sensor that was right over it, so I replaced that, replaced the plugs, etc. The plug marked by the ECU as misfiring was white (like pre-ignition white, or fuel-fouled). The other five were all black, like oil-fouled black, or carbon build-up black. The new spark plugs worked a lot more than the old ones, so it's backfiring like a MF now, but no more misfire (I fixed that!).
So I sprayed my soapy water looking for a vacuum leak, no luck. A vacuum leak that caused this problem would have to be huge. Still haven't ruled out the MAF sensor, but I'm not getting a code for it.
I did the cheap check of fuel pressure by pushing the schrader valve on the injector rail and got very little. So I just replaced the fuel filter (regular maintenance that I haven't done) on the reasoning that it probably needed one anyway, and the snake oil might have tore up the old filter and clogged it. I unhooked the front line first, the one that would be on the opposite side of the proverbial clog from the fuel pump, and got the regular explosion of gas you expect in a pressurized line. Naturally, this didn't fix it, and it's currently showing a possible line clog between the fuel filter and the fuel injector rails. Since there are rubber fuel lines that were near the fire, that would point in that direction. But the catch is I don't have a fuel pressure tester just yet (I'm going to order one, but it'll probably be next month), at least not one that can test a fuel injection system.
Ok, so, symptoms:
- Accelerates, but no power.
- Power fluctuates at various points (20mph gets a jump, again at 35)
- Backfiring through the exhaust.
- Engine codes: p0402 (EGR valve open too much), p0302 (cylinder 2 misfire, should be fixed but I haven't cleared the codes yet), p0174 (Bank 2 lean), and I think that's it. I'll be clearing the codes tonight and seeing what new ones appear.
- Fluctuating idle, leading to stalling at idle
- Near stalling during the weak spots in the acceleration curve
- Huge vacuum leak I still haven't found (heh)
- Bad MAF sensor, but no code for it.
- Bad fuel pump
- Clogged fuel line
- Bad fuel pressure regulator
So, my current working theory is that there isn't enough fuel hitting the fuel injector rail, so the computer is overcorrecting by opening the injectors longer than it should, leading to the occasional backfires, but otherwise running lean, although I don't have a reason why the bank one sensor isn't also reporting a lean condition.
Any other ideas?
