2005 xc70 misfire, cylinders 2 and 4

mrscullini · Post by **mrscullini** » 10 Jan 2015, 21:28

the car has about 145k on it. we have not had one issue with the car since we bought it from jrl with about 96k on it, it has been a great car.

on the highway this afternoon running at about 70 mph, 3000 rpm. idle got a little erratic, cel flashed a few times and power dropped. pulled off the highway, idle was a little rough. happened to have my scanner with me, pulled a p300, 302 and 304. cleared the codes restarted the car, seemed to idle smoothly so i drove home about 40 miles with no problem.

any thoughts? i will pull the plugs and check each cylinder tomorrow.

mrscullini · Post by **mrscullini** » 11 Jan 2015, 08:21

this morning all seems normal. no pending codes, idles smooth at about 650 warmed, revs up smoothly. will pull the coils/plugs this afternoon.

is there a way to simply test coils with a multi-meter?

draser · Post by **draser** » 11 Jan 2015, 15:39

Could you hook up a scanner to read fuel trims, o2 sensors, and maf signals? Also do you lose coolant? There's no good way to test coils with regular meter. Coils are step up transformers and when they fail they develop leaks secondary to primary so you'd need an insulation test. You could try the ohm meteron it's highest scale and measure between the pipe and any of primary wires, but probably reading will be infinity.

mrscullini · Post by **mrscullini** » 11 Jan 2015, 16:02

Thx draser. I'll see if my scanner has o2, maf capability. It is an autel us703.

What should those readings be?

Post by **IVIUSTANG** » 11 Jan 2015, 16:41

you could also swap the coils around to different cylinders and see if the misfire follows the suspected coils.

Jesse

mrscullini · Post by **mrscullini** » 11 Jan 2015, 17:39

thanks guys. the misfire is gone, it's now running "normal". no codes, no pending codes after a few drive cycles today.

here are some numbers i pulled with the scanner. no idea if they are in a normal range. numbers were pulled after about a 20 minute drive at 60 mph and idling in the garage.

ECT= 95 degrees C
IAT= 50 degrees C
Spark Adv= -1.5 deg to 3.0 deg
MAF= 2.69 to 2.83 g/s
RPM= 659 to 676
O2B1S2= 0.09 to 0.745 V
O2S11= -0.137 to 0.07 mA
CATTSM= 336

any insight is much appreciated.

draser · Post by **draser** » 11 Jan 2015, 18:17

MAF is similar to mine, o2 sensor 2 has normal levels, all others are normal values. For a misfire is good to know fuel trims to determine if engine runs lean or rich. For a normal running engine fuel trims will bounce around zero. Any change in mpg?

mrscullini · Post by **mrscullini** » 11 Jan 2015, 18:53

draser wrote:MAF is similar to mine, o2 sensor 2 has normal levels, all others are normal values. For a misfire is good to know fuel trims to determine if engine runs lean or rich. For a normal running engine fuel trims will bounce around zero. Any change in mpg?

thanks. no change in mileage. what are the fuel trim abbreviations or notations on the scanner? i will check them.

mrscullini · Post by **mrscullini** » 11 Jan 2015, 19:44

draser wrote:MAF is similar to mine, o2 sensor 2 has normal levels, all others are normal values. For a misfire is good to know fuel trims to determine if engine runs lean or rich. For a normal running engine fuel trims will bounce around zero. Any change in mpg?

i've got the following, not sure it is the fuel trim..

fuelsys1= cl
fuelsys2= -(dash)

draser · Post by **draser** » 12 Jan 2015, 05:59

Short term fuel trim -STFT, long term - LTFT. Can you inspect coil connector for 2, 4 to make sure wiring is good condition, conn clean - maybe spray some cleaner?