# Bad miss in 03' 150 4.6



## tomcatt (Aug 10, 2004)

I had a misfire on my truck, took it to autozone, they put the code scanner on it and showed I had a misfire on cylinder 4. I changed all 8 sparkplugs and COP's. This was due....I had 80,000 miles on my truck with no problems. That wasn't even 2,000 miles ago. Now my truck feels like it's starting to do the same thing. Idle's a little rough, stutters uphill a little and when I accellerate. I can still get to highway speed and drive with no problems. I'm drawing a blank. 
My truck also sits during the week and only gets driven on the weekends. Please let me know if any of you have a clue to what this could be.


----------



## Profish00 (May 21, 2004)

not sure what COP's is, but did you Replace/inspect the cap and rotor, get new plug wires also.


----------



## Roby (Jul 12, 2005)

COP = Coil on Plugs. No cap, rotor or wires on this engine. Check for a coolant leak that allows coolant to puddle in the spark plug hole that is covered by the c.o.p.s. It is common for coolant to accumulate in the passenger rear spark plug access hole on these engines if there is a coolant leak at the hoses to the heater core or the thermostat housing. This will cause the coil to short out and create a misfire condition.


----------



## libertyFF (Jul 29, 2007)

I have had this problem several times with both of my 5.4liters. 4 of the coils have went out with one of them having already been replaced. O'Riely has them for 50.00 with a lifetime waranty. A fellow 2cooler told me to check Summit racing @ $35.00, unsure of their warranty. If the Check engine light is not on it will not show a code for the reader. Pull a heavy trailer or "dog" your truck so it will come on. Then you will know which cylinder to replace the COP on. Good luck. PM W/ ?s


----------



## V-Bottom (Jun 16, 2007)

*Throttle Body Cleaning*

IDLE ROUGH??? Go to Auto Zone and pick up a can of Throttle Body Spray cleaner. Take your intake hose off from the throttle body assy., spray the entire inner assy. and the throttle plate very good. Stick your finger inside the assy., pull the plate forward and spray the back side of it to. Wipe out all the soot it dissolves. I did mine twice to fully clean it. What my 4.6 did was idle too low and rough, (525rpm) but ran ok when on the road. Your air intake sensor is sensing throttle is not positioned correctly and trying to compensate. My engine light came on and indicated the throttle body assy malfunction (so to speak). After spraying mine, rpm went back up and engine light finally went out on its own. They are made to do just that. Computer will reset itself over time. I recommend everyone, just to pull the hose and clean it evrynow and then. I also put in a 20 oz. $11.00 blt. of Techron fuel/ engine cleaner. Great stuff. I didn't add this to a FULL tank of gas. Added btl. to a little over 1/2 tank to make it more concentrated. Will not hurt a thing. All this was recommended to do by my favorite mechanic here in TC. IT WORKED...........................


----------



## Roby (Jul 12, 2005)

Throttle body cleaning is not necessary on these engines. If you look closely, there is a yellow sticker on the throttle body that states "do not clean throttle body" or something to that effect. The throttle body is coated with a substance that is supposed to reduce deposits on it. In addition, there is a hole in the throttle plate that allows for air flow in the event the plates were to be completly clogged. This allows the engine to get enough air that the proceessor can still control the idle speed. If you clean it with a throttle body cleaner, it will remove this coating. If you want to clean it, just wipe it clean with a rag, do not use any solvents on it.


----------



## birdband01 (May 25, 2006)

My '03 Chevy 5.3 has been in the shop for 2 weeks now! Their baffled, thinking I might have some kind of vacuum leak. It does the exact same thing w/idle rough and will barely get up to speed, exhaust smells really rich, runs fine at 40mph and above. What should suggest to my mechanic? (shouldn't have to I know but it shows nothing wrong when connected to computer) He also said my K&N air filter should be taken out cause it let's too fine of particles through intake. True? I feel your pain man! Irritating!


----------



## bwguardian (Aug 30, 2005)

birdband01 said:


> My '03 Chevy 5.3 has been in the shop for 2 weeks now! Their baffled, thinking I might have some kind of vacuum leak. It does the exact same thing w/idle rough and will barely get up to speed, exhaust smells really rich, runs fine at 40mph and above. What should suggest to my mechanic? (shouldn't have to I know but it shows nothing wrong when connected to computer) He also said my K&N air filter should be taken out cause it let's too fine of particles through intake. True? I feel your pain man! Irritating!


The problem with the K&N's on gasoline engines is that they such all that oil over the sensors and mess everything up...diesels love them though.


----------



## bk005 (Feb 23, 2005)

bwguardian said:


> The problem with the K&N's on gasoline engines is that they such all that oil over the sensors and mess everything up...diesels love them though.


Except for dusting Turbos.


----------



## birdband01 (May 25, 2006)

That's exactly what my mechanic told me. I just don't understand how it's possible since the filter isn't really saturated with the oil when you re-oil it. Should I just ditch the filter? The check engine light was on until I changed my 4 Oxygen sensors. But immediately after that the truck started running horribly! So weird. Just not sure what to tell mechanic or suck it up and take it to a dealership. ($ouch$)


----------



## bwguardian (Aug 30, 2005)

bk005 said:


> Except for dusting Turbos.


I am running them...and have been running them in all my trucks (5) with no issues. Actually, I bought a F-550 with only 34,000 miles with a dusted engine which ran the paper filter...it turned out to be a cracked intake hose. Replaced engine, intake hose, filter (with a K&N), and been great since.


----------



## bwguardian (Aug 30, 2005)

birdband01 said:


> That's exactly what my mechanic told me. I just don't understand how it's possible since the filter isn't really saturated with the oil when you re-oil it. Should I just ditch the filter? The check engine light was on until I changed my 4 Oxygen sensors. But immediately after that the truck started running horribly! So weird. Just not sure what to tell mechanic or suck it up and take it to a dealership. ($ouch$)


Ditch the K&N, clean the sensors on the intake side...the oxygen sensors are on the exhaust side (oil is burnt after combusted) and you should be fine.


----------



## tomcatt (Aug 10, 2004)

Thanks for the replies. I won't be able to do anything to my truck till this weekend, but I will definately check for coolant. Plug 4 was the trouble last time. Could this be fuel related since it sits for a week at a time? Or possibly a dirty air filter?


----------



## Hooked (Oct 15, 2004)

On my daughters '03 Expedition with the 4.6 this problem was caused by vacuum leak. Large hose about 18" long with 90 degree bend on each end had a hole in one of the 90 degree bends.


----------



## country7 (May 27, 2007)

I have an 03 f150 and have changed coil packs at LEAST 10 times, ford KNOWS they are a problem but refuses to recall and extended waranty doesnt cover them. Didnt know until i had replaced 4 or 5 that the packs themselves had warranties replaced several of them twice


----------



## GBFISHIN (Sep 14, 2007)

You know why people think dealerships are so expensive? It is because they spend all theyre money attempting to fix the problem themselves or having "Theyre Mechanic" try before taking it in to a dealer. So, by the time the dealer fixes the problem guess what, ya you have spent a lot of money and the only thing you remember is how much it cost to have your car repaired at a dealer. And another thing, Why isn't the guy at the dealership that actually fixes your car "Your Mechanic"? While your mechanic is scratching his head and other areas, the guy at the dealership just fixed another one. Sorry, just have to vent sometimes.


----------

