I have been very meticulous with my sons new to him 2001 ranger, I have a new issue though. It started stumbling a bit at idle so I pulled out the scanner. It gave me a code for cylinder 5 misfiring. I did the obvious and checked to make sure the boot didn't wiggle loose, disconnected and reconnected and it went away. Thought it was wierd but whatever. Its been a few days now it's stumbling a bit again so I scanned it again amd it gave me a cylinder 5 misfire again. So just for giggles amd repeatability I cleared the code and scanned again, now all of a sudden the missing on cylinder 5 is gone and it's missing on cylinder 1. I'm at a lose here. I am thinking it's possibly a faulty or intermitten issue with the coil pack. Does anyone know what the ohm range for the primary and secondary coils are? Figured I'd test for proper resistances before I check for good spark at both ends of the wires seeing as the boots are a bit stuck on a few. Figured I'd go ahead and replace all the spark plugs too. With all that said and asked, does anyone else have any ideas?

 

You posted in a 2019+ Ranger forum

So its a 2001 Ranger with 3.0l or 4.0l V6

Yes, spark plugs 1 and 5 share the same coil in the coil pack, but they are also wired in series, so one of the 2 wires or spark plugs could also can the "moving" misfire
1/5, 2/6, 3/4 are the matched pairs in a V6 engine, so with a coil pack each pair shares one of the 3 coils in the pack

There was a TSB, a long time ago, about early 2001-2003 3.0l Ranger that got a bad batch of coil packs, but that was 20+ yeas ago, so probably not that

 

Sorry, my fault for not posting details. Its a 2001 ranger with the 4.0 engine. It has a code for misfire on cylinder 1 as well as codes for running to lean on bank 1. I bought the truck from an older guy that decided to sell it after being put into long term care. He had tons of paperwork for the maintenance on the truck including a new motor and refurbished trans about two years ago. I dont know who did the work, all I saw was the receipts from oreillys. I can do a lot as far as wrenching goes but vacuum leaks and electrickery dumbfound me sometimes, this is the case here. it looks like the vacuum storage ball has been just randomly thrown under the hood due to a broken mount post.. I followed the vacuum line diagram but cant tell where some of the lines run. Some one has played with them a bit and uses a bit of "clever" engineering. I was really hoping someone with a bit more experience might give me some guidance on that subject. So yeah I guess it goes to say that there are a couple more problems than just a simple misfire. Maybe if I can get a better understanding about how the vacuum lines are supposed to be ran I would have a decent starting point. I do plan on pulling plugs and looking there as well as checking the pressure at the fuel rail to eliminate a fueling issue. I did the old school carb spray trick around the intake and some other questionable spots but didn't get any rpm fluctuations.

 

Misfires cause Lean codes, so the misfire is the source of a lean code, if its on the same bank, lean code is not the cause of the misfire

Lean(or rich) codes are from the Oxygen levels in the exhaust, so from the O2 sensor's voltage level after warm up
O2 sensors can ONLY see Oxygen
When a cylinder fires the fuel and oxygen is consumed, burned up
When a cylinder misfires the fuel and oxygen is not consumed so the oxygen is dumped into the exhaust and O2 sensor reports higher oxygen levels, i.e. lean

So focus on the misfire
Compression test would be a good start

 

Found the fix. Finally just said screw it, and pulled the plugs. I was so afraid of the boots ripping and then having the head ace of trying to fish the pieces out. Did it and all was fine. Anyway thought to myself for giggles maybe I should do a resistance check on all the injectors just for data comparison. All said and done looks like 1 is dead and 5 reads different than the rest. Odd thing is the misfire code was for cylinder 1. I am guessing 5 is intermittent and on its way out. Pulled the wires of the other end and checked spark at the source and the coil pack looks like its firing on all the plugs. Nice fat spark, I may have tried putting one on without turning the motor off, I was inpatient, and yes it zapped me. This big boy may have jumped a bit. Checked on the plug end and after a bit of clean up and re-gaping they are all firing perfect. Lets just say they were well out of gap spec, guessing who ever put the new motor in never bothered to check them out of the box. They might of worked fine the way they were but I figured if they were out might as well make it right. Anyway, just thought I would publish my findings, Hope it helps someone out. All I can say is i wish I wasn't such a scarecrow when it came to plug boots, to many bad experiences I guess. Happy wrenching to everyone!!!!