hi, new to the site. been looking ans serching till my eyes hurt, but no luck.
have a 02 expedition 5.4 shows #6 mis fire. so i replaced the coil still mis fire, replaced coil and plug, still mis fire, replaced injector and guess what still not firing. could it be a lifter? when you first start it up no mis then as it comes back down to idle it will start missing at about 850 rpm approx. when driving if you floor it it misses hard and if you stay in it it almost picks up and smooth out. please help

 

What brand of coil, plug and injector did you replace them with?
What did the plug look like that came out of there?
Was the PCM reset and cleared after each item was changed?

A simple way to check if you can get it to misfire while idling would be..
While idling and misfire, one at a time unplug the electrical connector of the #6 coil. Does it make the misfire worse? Or does it not change anything at all? If it doesnt change anything, then its most likely a bad coil. Do the same with that injector. Look for either one NOT to make a difference in the misfire.

Otherwise, you can swap the coil over with another cylinder and reset the pcm. Wait for the misfire to come back and see if it switched to that cylinder. IF the misfire comes back to cylinder 6, then swap the injector.. same thing, see if the misfire moves.

If none of that determines if its the coil or injector to that cylinder, your next step would be a compression check.

 

all parts are from advance auto. plug looked normal for 90k. yes the pcm was cleared. i can clear the codes and it will not miss for a few min. then start back. will a coil be intermitant?

 

they can be yes.


I was looking for brand names of the parts used. Not sure what brands advanced auto uses.

I would try to wait for it to be misfiring and use the procedure to try and pin point it. Takes about 10 minutes. Try to use either motorcraft coils, or coils from global automotive or uneek (whole sets for around $100). Also motorcraft plugs. These trucks/suvs dont take much of a liking to aftermarket plugs or coils.

I would suspect the "advanced auto" coil. For all I know, its a refurbished no name brand coil..? Not sure. Not impossible to be faulty.

Problem is, just replacing that 1 single coil, you might experience the phenomenon of the other coils going bad and other misfires showing up soon after... Its unexplainable, thats why its best just to purchase the whole set on ebay from global or uneek stores.

 

Check your connectors for the plug and injector well.....could be a wiring issue as well.

 

just swapped #6 which is showing bad with #1 changed plug to be safe still showing code P0356. took a spare coil and plug and pluged it into #6 to check for spark and it was firing the plug. there is a very faint tapping like a lifter from that side you think i need to go deeper or am i missing somthing.

 

Time to do a compression test.

 

I would double check the injector and make sure it is delivering fuel

 

how do i check injector? i removed the electrical plug checked voltage and had constant 12v to plug. should it be pulsing? working on compresson check my guage would not seal but even with a leak it showed 145.

 

If you want help , you need to answer the questions. I'll ask again , since Toyz already tried twice. What parts did you use ????????? How can you not know ?

Who makes the coil you bought and what spark plugs did you use ?

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Swap your injector with another to confirm as good.

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At-least compression test a couple more cylinders. You should have a comparison. Wrap some Teflon tap around the threads if it's just a little loose. Wrap it 3 times only.

What's the exact codes (DTC's) when scanned ? The numbers ..

 

Sorry about that i missed that request, just found out the autozone part is a BWD coil and injecor, it had autolight plug. i have since changed all that around and the mis does not follow it. changed plug to motorcraft just cause i had them handy. i bought a noid light and it will flash for about 15 or 20 seconds then go out. i checked and if you unplug injector and coil on #1 it does same thing. so is that maybe a shut down by ecm to keep from washing cylinder? going to check compression again with better gauge. i realy appreciate all the help here, feel like im getting ever so much closer.

 

compression check shows 125 psi. cant find what it should be. I let it suck in some seafoam i had and all that did was smoke up the shop really good. any other ideas

 

125 seems a bit low. But what matter more is how it compares to the other cylinders. Any chance you did all 8?

 

Seafoam can ruin your engine when used that way.

 

i wonder why seafoam recommends it that way then?