Hello guys, I'm turning to the experts here for some help. First a little background... 2001 V10 Excursion. History of periodically not wanting to start and slight miss the last year or so. Miss mostly occurred after rain or in humid weather. Only use the Ex for towing our camper, so it sits all winter until spring arrives. It doesn't get much exercise

Well, spring came this year and the Ex refused to start. Would crank, but not fire up. This has happened before and after letting it sit for a bit,it would normally fire right back up, but not this spring, she just didn't want to start. So I replaced the Crank Position Sensor, Cam Position Sensor and Fuel Filter. (I had bought these last year for the periodic 'crank no start' condition we were experiencing, just never got around to installing them). So I installed these. Truck still didn't want to start, it would crank, just not fire up. It actually did start one time for about 10 seconds, then died. So after more analysis, I decided it was the Fuel Pump (no sound out of tank when engaging the key). So I then spent the rest of the day replacing the Fuel Pump (what a job!), O'Riely's was the only place that had one in stock, so I was stuck with the Precision brand #E16040. After putting her all back together, turned the key, system pressurized and she fired right up and she idled like a kitten (minus the periodic quiet miss she always had due to a bad COP I'm sure).

Anyway, I thought I was good to go, I let it run for about 20 minutes at idle to charge up the battery, then decided to go for a ride to the store. immediately, the truck would violently jerk after about 1700 RPM, backfire, then recover. I say it would recover, because it would never stall, but it would NOT go over 1700 RPM. It's as if the engine loses spark right at 1700 RPM. Even the Tac loses electrical just for the second that it's backfiring, then it regains juice and registers RPM. Parked it for the night, feeling defeated and went to bed.

Next morning, started it up. She idled good, took it for a spin around the block, no more 1700 RPM cut-out. That's strange I thought, until the engine warned to operating temp. Now the 1700 RPM cut-out returns. So now I know it's only happening when the vehicle is warm. From cold start, she seems fine.

So now I'm wondering, is it one of the parts I replaced is bad (CrankPosition Sensor, CamPosition Sensor, Fuel Filter and/or god help me, the Fuel Pump).

I don't think it's fuel delivery, just because of the backfiire, I believe this is raw fuel in the exhaust igniting, I really think it's a spark/electrical issue. I'm leaning towards COP issue as it's always had a slight/quiet miss, but the behavior it's displaying now, is much more severe, it's almost as if half the engine COP's are failing in unison at 1700 RPM when it's warm. So I'm unsure whether I should start replacing COP's as these are expensive.

I have to let it cool down and I'm going to take it up to have it checked for codes, but I'm seeking any insight from the community? Anyone else experienced this behavior? Any things I can check before playing the expensive game of COP replacement?

Thanks! Sorry for the long post, but wanted to give as much info as possible.

 

Ok, update, just got back from AutoZone, scanner pulled code P0320.
They tell me this is a Crank Position Sensor Fault.

Did I install a new/bad sensor? Got down under the vehicle and pulled the plug off the Crank Sensor, looks wet, like it has oil in the plug, that doesn't seem normal. WTH?

 

Well, turns out the brand new Crank Position Sensor isn't reliable. It can't reliably sense the crank rotations over 1700 RPM. Put the old one back in and Bingo! She run's like a champ!!! Assuming my 'Crank no Start' issue was the fuel pump all along, because the old Crank Position Sensor works just fine!

If anything, hopefully this thread is helpful to someone in the future!

 

Seems like it is never a good idea to do a shotgun approach to parts replacement.....

 

Glad you figured it all out! All withing 12 hours even. I agree a shotgun approach might not be the best option, but I've been in your position. All you want it to do is work. Also goes to show, sometimes the parts you can get can also be faulty.