Misfire with fuel Cut Off

Doozy · #1 02-07-2009, 02:07 AM

About 6 months ago my wife decided we needed an extra safe SUV because we had a newborn on the way. No questions about it, X5 was the choice. 2001 4.4 liter, 72k miles, well taken care of, drove like a dream, until it lost a little power, started shaking, SES light always flashing (only goes solid when i decelerate for a few seconds). I bought an OBD Scanner and all the codes were "misfires due to fuel cut off". I would reset them, they'd come on again, but be different. All Misfires, but different cylinders. It might be cylinder 2, 5, and 8 one reading, then 2, 3, or 6, the next reading. No rhyme or reason to it. Codes: P1343 P1345 P1347 P1349 P1355 P1357 at one point or another.

What I have done:
1. Replaced all spark plugs. 4 prong NGK, same as what was in the car.
2. Changed the fuel filter
3. I had two large vacuum hoses that were disintegrated and flat with holes all over them on the back side of the engine (top of intake manifold), so i replaced those too.

The car shakes the exact same, but now has a little more power. Now, the code is consistent. Its P1357 Misfire Cylinder 8 with Fuel Cut off. I'm not sure where to start next. Guessing costs me too much money, so i'm seeking professional help (x5world, ha). My guess would be clogged injector, bad wire to injector, coil? I'm not sure how to do a voltage test, but i do have a tester. Can someone please piont me in some sort of direction. I promise I'll post my results (pet peeve when people don't!)

Any Suggestions would be greatly appreciated.

One thing positive, with the car shaking because of the misfire, its puts the baby to sleep faster!

supersteve · #2 02-07-2009, 08:52 AM

Each of the spark plugs has it's own coil. A simple no cost thing to try first is swap the #8 coil with another and see if the problem follows the coil.

swissfrank · #3 02-07-2009, 09:03 AM

hmm, could be a damaged wiring harness, vacuum leak or a dirty MAF. Let me sleep on this one...

Weasel · #4 02-07-2009, 09:39 AM

If the missfires are random, I wouldn't suspect coils... but it may be a fuel pressure issue... have you read the running pressures? (at idle and under load) The fuel rail has a tire valve sized valve to hook to, the same size as old fords, so the cheap fuel pressure testers from the parts stored will work.

Doozy · #5 02-07-2009, 02:45 PM

Quote:

Originally Posted by weasel56

If the missfires are random, I wouldn't suspect coils... but it may be a fuel pressure issue... have you read the running pressures? (at idle and under load) The fuel rail has a tire valve sized valve to hook to, the same size as old fords, so the cheap fuel pressure testers from the parts stored will work.

It was inconsistent, but after I replaced the vacuum hoses and the fuel filter, its consistenly 8. I'll try to look over the wiring harness and check for more vacuum leaks, along with changing around the coils.
Thank You for the input

Weasel · #6 02-07-2009, 07:23 PM

If it is consistantly cyl#8, simply swap the plug to cyl 7 and the coil to cyl 6. Then clear it and see which part it follows.

supersteve · #7 02-08-2009, 07:44 AM

Weasel,

Refresh my mind. The cylinders are numbered 1-4 on the passenger side 5-8 on the driver side. Bank 1 passenger side. Bank 2 driver side. Correct?

thanks,
Steve

Weasel · #8 02-08-2009, 11:55 AM

Yep, you got it!

Doozy · #9 02-23-2009, 02:14 AM

Ok, so with the misfire finally becoming consistent, I replaced the Coil and its gone! Runs better than ever. What I don't understand is how several misfires turned into 1 consistent. I think either the vacuum lines or the fuel filter was the problem and thats what fixed it. At the same time, I also swapped the plugs so I'm thinking while doing that, I somehow damaged a coil? Or maybe it was coincidental that one went bad at the same time? Thanks for all the help.

Doozy · #10 02-23-2009, 02:15 AM

Ok, so with the misfire finally becoming consistent, I replaced the Coil and its gone! Runs better than ever. What I don't understand is how several misfires turned into 1 consistent. I think either the vacuum lines or the fuel filter was the problem and thats what fixed it. At the same time, I also swapped the plugs so I'm thinking while doing that, I somehow damaged a coil? Or maybe it was coincidental that one went bad at the same time? Thanks for all the help.