well to start off, i posted this in the SD section and ended up with NO RESPONSES. no tech support what so ever.... now i know why i hang out in the good sections (Excursion / 6.8L)..... any way off to the troubles.....

TRUCK: 2002 Excursion, 4x4, V10, 152K on the clock, prior govm't vehicle (forestry in Tx), bought with 140K, service records to boot, plugs changed at 100K with OEM's, oil every 3K (supposedly, lol).

symptoms..... the truck would cut out when pulled up to a stop light, and the OD "off" light would flash.

well i researched as much as i could, and found 1/2 dozen threads on a few other forums that started in this order 1) alternator could be going out causing interference with the sensors 2)bad sensor (either the VSS or the OSS), then to internal trans problems, torque converter problems, and so on..... i read in one other topic that a "MISS FIRE" will aslo cause the fault in the sensor... well our Snap-On "MODIS" computer only showed code P0720, ran in in drive mode, test mode, every mode i could think of and what i could make it do. ran the miss fire test, injector test, you name it i went over it on that scan tool....... still only a P0720.... FINALLY after 2 weeks of chasing this on the scan tool, the CEL came on, and P0722 code was thrown..P0722- no out put signal from the OSS sensor......BINGO FOUND IT.

well with in these 2 weeks i took my alternator in to a VERY widely known reman shop in this area...... come to find out this was a "slap on" alternator, not meant for this application. well any way he benched it, installed new bearings, new diodes, and regulator ect..... $65, and i know it's done right, no biggie.... still chasing this studder and stall gremlin.......

now we get to the P0722, the alternator was not the problem, verified that, still money well spent. now on to the OSS sensor (this is the one located at the rear of the tail shaft of the transmission). the MODIS gave me some trouble shooting parameters to follow when testing the wiring and the sensor it's self. checked for proper resistance of the sensor..... it was "slightly" more than recommended, so DING DING DING we have a WIENER...... ford part $20, not bad. installed sensor....... STILL acting the same..

well in the midst of the parts ordering and scan tooling..... i ordered new plug boots, and plugs threw work (heck of a discount). now i know this is a sin in the ford world BBBUUUUUTTTTT....... the place i work has contracted parts that we order from dealers and vendors..... so threw NAPA the Champion platinum plugs were $1.80/ea..... i ordered 10! (if you say that you wouldn't have, i bet you would have at least giving it a few thoughts!!) well with the plugs ($1.80/ea), and the boots ($1.99/ea), i have $40 tied up in tune up, $20 in sensors (might not have been needed, but reassuring to have it new), and $65 tied up in Alternator work.......JUST TO FIND OUT I HAD 7 OUT OF 10 BOOTS THAT WERE UNSERVICEABLE, AND 10 PLUGS THAT HAVE SEEN THEIR BETTER DAYS!! after 52K since their change (records say they were changed at 100K) the smallest gaped one was .060 all the way up to .066 and .068, and these are factory MC plugs too.

i installed all the boots/springs, and plugs this evening, and the cutting out is GONE!!

now for a side story. when i bough the sensor, i come to find out that the service manager lives about 3 blocks from me (chatted, traded info ect)..... well when i put the sensor in, i figured i'd use up a "buddy call"...... sucked it up, called him and admitted that the sensor didn't fix it, nor did the ALT (which he said he'd never heard of that one, i told him the forums had haha), and he said you're probably waisting your time with the boots, because he'd put a 6pack bet that i have COIL(S) going out. he said he'd order me some if i wanted him to at the "employee" cost ($32/ea is what he said).........ME: in my head HEEEEECCCCKKKKK no that's $300+ bucks, have to give me a couple paychecks on that one...... TOLD HIM: let me put all the plugs and boots in and see what i come up with. he said cool, halla back after your done. i called him up, "ITS GONE MAN"......him "NO S**T.....YOUR KIDDING...... so there's no cutting out, no miss, no CEL, no flashing OD light"........ i told him as of right now NO, he said he wagered that i had coils going out because it's a common problem, especially after so many miles on OEM coils.....

so the end result is...... Good coil boots = good sensors (in this case), service mangers of 20+ years DO once in a while learn something new, and i passed on the 6 pack for a bottle of my choice, and he'll bring it over next time i throw some steaks on the grill, LOL!!

the 10ER is back in commission fella's!!

 

Glad you resolved ,made a friend and we learn something.
Yes these plugs and boots create all kinds of bizarre issues,don't they?

 

That's one long tale, but one worth telling

Very interesting. I wonder if it was the misfire itself, or the spark going elsewhere and interfering with the sensor? Check your grounds lately?

 

yes sir!! well to be 100% honest i checked a hand full of them, i'm sure there's a few of those little ground straps i may have missed, but i got to the majority of the ones i could see.

well i researched the issue some more slightly at work today with our "on demand" vehicle maintenance system, that is a tech manual for vehicles up to 09.... i searched for possible PCM related issues, ground issues, and trans related issues........ all i could really dig up was that the miss fire from the coil to the manifold would make a ground connection and interfere with sensor readings.....when the truck was "shuddering" while stopped at a light, the arc from the coil to the manifold was trying to make the torque converter clutches lock up.... well when the arc was strong enough or a direct hit it would lock the converter while stopped, trans in 1st gear, thus making the truck stall (can't lock up the converter in 1st gear).

this would lead me to believe that the arc off the coil was completing a ground circuit that was tied into the OSS sensor. the torque converter clutch pack is locked via ground, not power. so it has power going to it all the time but only actually locks up when a ground to ground connection is made.

it may have been the combonation of sensor going bad and old plugs/boots, but i can tell you that i put that new sensor in and it really had no seat of the pants difference from the old one, truck still shuddered when at a stop, stalled on me once out of 4 different stops.... installed new boots/springs, and plugs and it's floating like a Cadillac and stinging like a Beemer again!

 

Also, think about the voltage that comes back out the primary side of the ignition coil and hits the PCM, when the secondary side doesn't fire. That EMI (interference) going back to the PCM is not a good thing overall.

Funny how all this stuff works together, eh?

 

Do you know the main ground locations to check off the top of your head? The two on the top of the firewall are tight but where else is a good place to look?