supercrew_guy

Ok here is the skinny I just bought my 1st ford it is an 03 F-150 Super Crew with the Triton 4.6 when i got it it ran fine for 4 days then it started missing i was like ok Plugs it has 103000 miles on it so i put plugs in it..Still missing ok then the coils from what i can tell the coils are fine all seem to be firing good so i was like ok Fuel so i put a new fuel filter on it it started running better but the miss was still there so i had the fuel pressure checked it was at like 30psi so i found out that that is to low so i put a new fuel pump on there and now it seems like its worse then what it was before hand HELP ME PLEASE!!!!!! Im at a loss.....I havent even had the truck a week

Kattumaram

Run a scan of the system and see if it throws a misfire code.
Possible causes of a misfire are: plug, coil, injector, harness, PCM.

Fuel pressure limits are: Key On Engine Off, 30-45psi. Engine Running, 27-42psi. Pressure leak down when engine is just turned off is less than 5psi in five minutes. If the system fails the leak down test an injector is probably leaking.

supercrew_guy

thank you for your help i will try that and see what happens

supercrew_guy

the fuel pressure is fine....but i still have the hesitation not sure what is causing it the coils checked out fine i do not have a check engine light on...im lost

Loyyd

Wife's 03 4.6 had/has same problem. After replacing plugs/wires/ign. module...turned out to be a problem with the upper intake manifold gaskets.(Which apparently is widely known to any mechanic you ask...after you mention the intake gasket.heh) They're known to fail and every supplier on the block sells the re-designed gaskets. Truck had a miss and kept giving lean codes sporadically. Replaced upper and lower intake manifold gaskets to be sure and problem went away...mostly.

Truck now has a bit of a gremlin-esque miss/stutter right around 2k. Won't do it ALL the time, just enough to hack me off. Fordmechanicfriend tells me the 4.6 engines prior to an '04 yearmodel redisgn were known to be tempermental...so much so he is adamant I get rid of it prior to the 150,000 mark.

I've done the same steps you have. Additionally I ran some pretty strong ratio'd injector cleaner thru it and changed where I buy gas. Now it only spits occasionally if you load the engine in too high a gear.(manual transmission) Gas mileage is still atrocious though. Perhaps yours and mine have developed the same split personality...

Could be worse, my fathers last three f150's (04,06,07) ALL developed random computer glitches around 100k. Seriously, lights go on and off, radio comes on and off,changes stations, and the climate control fluctuates. Seriously makes me appreciate my 08 f250 4x4 7.3. Over 200k and nary a problem yet...so far.

drof 1

hahaha, sounds like a new Steven King novel coming up here. The Ford haunting, lol.
Thanks for some additional info offered here on the 4.6, (I'm searching problems of the 4.6 triton), some of which you may have answered for me.

Sir Icemelted

Okay i had the same issue on a Ford Expedition 4.6 Triton. I do not like the design and how they put the spark plugs down in the hole. My Dad always told me it is usually the the most basic of problems mechanically that gives you the most trouble.

I changed coils, spark plugs, fuel filter,tanks of sea foam,checked the fuel injectors for the clicking with the old trusty 2 foot water hose (like a stethoscope)that water hose also helped change the plugs, cleaned throttle body, cleaned EGR , Idle Control, checked my plug wires for the night time fire works and made sure each plug wire was firing at the spark plug end. I did notice a little rust on two back spark plug wires at the plug end (cleaned them with emery cloth). Nothing got rid of the missing although sometimes it would go away but always came back over time. Would miss at idle or acceleration or under a load very spastic and no pattern.

Then I remembered my dads words and also how he told me to ALWAYS use Die Electric Silicone Lube on both ends of the plug wires. That solved the issue! The design of the spark plug placement causes moisture to biuld up on the plug ends, that then leads to rust and corrosion and it does not take much of that to make your miss. Now you can clean it off but without the Lube the missing just comes back over time.

Now another thing I did eventually replace my spark plug wires but only after the Die Electric Lube solved my issue. I done it because the new spark plug wires are made to fit snugly into the spark plug holes to help prevent the moisture issues. The old spark wires did not and they had no flange at the top of the boot to further prevent moisture from getting in the hole. So the old spark plug wires worked but allowed condensation to cause a bad connection and getting that crazy missing over time.

Been a year since that $300 hundred dollar lesson that could have been solved by just listening more closely to my Dad and using that Die Electric Silicone Lube. Wanted to post this to possibly help others with the wisdom I once ignored.

Ha Ha hey I really should blame it on the parts store for trying to pitch sell me that little pouch of lube all the time! That gets on my nerves so hell no I will not use that stuff! LOL !