rmdailey

2003 Supercrew 4.6 v8. 154K Stock.

I recently started having a misfire on my F150. I figured it was time to change the spark plugs so I bought 8 and replaced them myself. I'm a DIY'er but my knowledge of auto maintenance is basic at best. It ran like new for about a week ~250miles then started running very rough.

I went to the Autoparts store and had the codes ran. Cylinder 7 misfire. So I installed a new coil. Fixed it for about an hour ~40miles. Now it's even worse.

I've parked the truck and borrowing my FIL's old truck until I have time to work on it this weekend.

What's next on trouble shooting this?

mbb

Does it happen when driving or worse when cold start?

Idle or driving? What speed/rpm?

Are you missing any coolant>

Have you checked fuel rail pressure is in spec, changed fuel filter, etc?

Are the plugs ONLY factory motorcraft?

Checked all PCV and vaccuum hoses and PCV valve?

rmdailey

Based on what I was able to determine today after work (with my FIL's help), I'm losing coils. Cylinder 7 is back up and running after I cleared the codes. Now it's cylinder 5 that is misfiring. I fear that I'm going to be losing coils one after the other. That's $60 a pop for motorcraft. Still better than a truck payment...according to the wife at least.

Yes plugs are motorcraft, PCV and vacuum system was repaired about 10,000 miles ago.

jethat

They do that. Go over to Rock Auto and order up 6 more Denso coils. Denso is an OEM supplier and at Rock auto if memory serves me the are less then $30. I have denso coils on my truck and I compared them to the motocraft and they are Identical right down to the Made in USA stamp.

rprater25469

I've tried different coils and realized the expensive way to just buy the motorcraft coils,also I put electric grease in the plug to coil,also go to take negative post off and reset system

TheBeast97

recheck you pcv and make sure its tight going into your valve cover. Probably coils though. I just got a nice OEM set of 8 out of 2003 at the scrap yard last week for $90 and my truck is running 1000% better.

jcx1803

I just purchased Delphi Coils on Ebay for $13 each and my truck is running like new. Autozone charges $60 for the same Delphi Coil. So I just bought all 8 for something like 108... Did the whole tune up for $130. Get your parts on Ebay the parts stores are a joke and the rape your wallet.

poorboy1964

Interesting Ford outsources these to someone like all their parts Ill do some digging to see if I can find who makes them for ford

R&TBabich

Are you sure the coils are going bad?
The COP assembly has 3 parts - coil,boot,spring.
The coil should far outlast the boot/springs.
With 154k the boots are probably going.
Make sure there is no moisture getting down around the plugs.
You can get just the boots/springs from NAPA - Belden 702418 for $6 ea.
Rock Auto has the boots/springs from DENSO 6718110 set of 8 for $24.
Rock Auto has the COPs from DENSO 6736000 for $23 and MOTORCRAFT DG508 for $41.

guyina4x4

you can't use too much of this
https://www.amazon.com/Super-Lube-91...lectric+grease