Hello Gents, been crawling all over this forum on the P0352 code and related threads for insights to my 'gremlin'. Most threads were several years old so Im hoping a tech or someone with the same gremlin has an insight.

History

06 F250 Triton V8, 151K Miles. Everything is stock. Have done all maintenance myself at required intervals or sooner. Just replaced COP after noticing a slight miss this past summer (they were due). Never a code until just a month ago (0420) both cats replaced. Ran great for several days until 0352 code shows up. Pull #2 COP and swapped with #1, same code. Utilized a noid light to see if PCM is giving a command, it lights up like a Christmas tree. Also checked associated injector for PCM command and all is well there too. As a 10 year journeyman electrician experience tells me the problem isnt always under you nose! Ive pulled apart connections where the common wire goes into the fuse block just for giggles and all is good there as well.

After putting it all back together and a 15 mile test drive there are no codes. However, when coming to a stop the RPM will dip 50-100 rpm below idle before coming back up.

Thoughts, theories, suggestions would be appreciated.

Chris

 

Hi Chris, welcome to FTE!

I'm no electrical expert, but I was having similar trouble with a P0353 code in my old '97 Lincoln that shared lots of parts with the F-series trucks. Couldn't find any connection issues, and swapping the coil yielded the same code and misfire. Ended up fixing the issue with a junkyard PCM. The coil drivers for this generation 4.6L V8 were in the PCM.

I believe the coil drivers are in the PCM for your truck, but I'm not certain. If so, I'd suggest checking Car-Part.com--Used Auto Parts Market to see if you can get a used one from a junkyard at a reasonable price.

 

Thanks for the input Tom, Ive utilized several COP (I kept the old ones just in case) swaps but my problem remained. Not sure if inspecting several connectors helped but the issue has not come back in the few short miles Ive driven it. Ill know more this after noon on a road trip to my daughter softball game.

Chris

 

A P0352 code can also be a spark plug issue. Try swapping plugs to see if the problem follows.

 

Redford, I had the same idea. I pulled all plugs on that bank to see if there were any clues. This set has around 15k miles and look nearly brand new yet. I did a decent in town drive to my daughters soft ball game and it ran like a top. Hopefully, I chased the gremlin away but should it come back I'm hoping to have more ideas on where to look. Thanks for the input!

Chris

 

Redford, I had the same idea. I pulled all plugs on that bank to see if there were any clues. This set has around 15k miles and look nearly brand new yet. I did a decent in town drive to my daughters soft ball game and it ran like a top. Hopefully, I chased the gremlin away but should it come back I'm hoping to have more ideas on where to look. Thanks for the input!

Chris

 

What plugs are in it?

 

Redford, I currently have autolites. I've read there's been some talk that the quality they once had may not be there. So that's a consideration if that's where your question was headed.

Chris

 

Correct. There have been many threads which conclude that anything but the Motorcraft Platinum plugs don't work very well in the Modular engines.

 

I think the brand of spark plug is a red herring. I've read thread like that as well Stuart, but I've used both Bosch and Autolite plugs in modular engines without any issues.

I'm unsure of the OP's truck, but the diagnostic tree for the primary ignition on my old 4.6L made no mention of anything in the secondary ignition circuit. Every pinpoint check was at the coil, harness, or PCM. I've never seen or read anything reputable saying that a spark plug can cause a primary ignition fault. But then again I don't have the factory manual for the OP's engine either.

 

I've not seen any facts that would point to the autolites quality being sub standard. But it's not to say that some motors may "prefer" not being run on anything other than OEM.

As a side note, my motor did stumble a bit yesterday and was acting like it had before but no CEL.