Need Help! Code P0306. Already Had Plugs Replaced

[DanTheMan97]

Any mechanic worth his sockets checks a new spark plug against an old one coming out. You match thread length, porcelain projection length. As far as a spark plug coming loose due to a heat range too hot, the answers no. What usually causes a loose plug is a mechanic that doesn't know how to torque them down. When you stated the parts person at Oreillys gave you the newer plug, they gave you a one piece plug that won't break on removal like the original Ford one. Are you doing the repairs? Or a shop?

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I guess I'll Start form the beginning to avoid any confusion. So I bought the expy with 119,800 miles. It had a few minor non related issues, but the motor and trans seem as they should. Oil was a little dirty, but not black. etc etc. after a couple thousand miles I slowly started to notice it struggle/studder more and more until finally the engine light would flash occasionally and code P0302 (cylinder 2 misfire) showed up. At 126,600 miles I decided to bite the bullet and take it in to a shop to get all 8 plugs replaced. I would've considered doing it myself, but i was afraid of breaking off a plug. The shop did say none of them broke off, so I supposed they could've been replaced already before I bought the vehicle. After taking it to the shop, the issue seemed 95% better. Acceleration was back, pulled trailer great again. After about 4,000 miles I noticed the issue showing back up again, I figured it was probably a COP starting to go so I kept driving till the engine light came on. This time Code P0306 showed up, so I replaced cylinder 6 COP (132,000 miles). That seemed to help a bit for maybe 100 miles. I thought oh hell, maybe the COP was defective from the factory so I threw a different COP on #6 to no avail. After that I proceeded to change the fuel injector as that was the only thing on cylinder 6 that hadn't been replaced yet. Still no difference. Before I moved on to diagnosing elsewhere in the vehicle I decided to replace the plug as that was the only thing I didn't physically replace myself on that cylinder. Upon doing this is when I discovered the plug being loose & burnt.....all this info should be in my last reply

Fast forward to today, and its at 135,800 miles. Hasn't showed any more bad symptoms & no check engine light. Not sure if its just my imagination or not but seems not quite as powerful as it did immediately after swapping cylinder 6 plug. Thinking about pulling the plug again in another 2 or 3 thousand miles just to see what it looks like.

So to answer question, the shop "changed all 8 plugs" originally when problem showed up the first time and I've been working on it myself ever since.

Hope that clarifies it better

 

[Big White]

As I stated a couple posts ago. I have doubts the shop replaced the plug. If they did, they did not do it right. One or the other. I carry a spare COP and tools to change on the road if need be.

 

[DanTheMan97]

As I stated a couple posts ago. I have doubts the shop replaced the plug. If they did, they did not do it right. One or the other. I carry a spare COP and tools to change on the road if need be.

I would agree with you on that, it does seem fishy

 

[Trainmaster]

Whoooh Cowboy... Those plugs weren't changed 5K miles ago. Pull them all, replace them and the boots with the right stuff and you should be fine.

If that garage you paid to change them plugs is still in business, you can throw the eight of 'em through their window. You been snookered.

And forgot those cheap Chinese coils. Replace the bad one or ones with Motorcraft coils or you'll be chasing eight of them for however long you own that truck. Is it worth saving a few bucks to have to carry a coil wrench in yur trunk? Must really impress the babes:

"... hold on a minute Dear, just gotta change this here bum coil. Grab
me that wrench in the back seat. We'll be back on the road in five minutes..."

 

[1955moose]

I've heard of lazy/crappy mechanics skipping the back 2 plugs due to difficulty, but wow all 8! That's just dirty!

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