Hi guys. 98 F150/4.6/auto/just hit 180,000 miles. A few weeks ago I posted about my truck missing and hesitating until warm. The CEL came on so I had it scanned which showed a #5 misfire. I pulled the Motorcraft platinum plug and the electrode was nearly burned down to nothing. These plugs were only 16,000 miles old. I replaced the plug and it ran great for about a week and a half and did the same thing again. Just had it scanned tonight and another #5 misfire. I'll pull the plug tomorrow and check it out. Anyone know what the heck could be causing this? If this plug is shot too I've obviously got something else to look for. Only thing I can come up with is maybe the injector is bad and causing that cylinder to run lean. Any ideas are helpful. Jeremy

 

Your on the right track. Might have to put a coil pack in too.
Let us know how it goes.

 

Im having the same problem with my 99 5.4.
The codes read misfire #2 and #3.
I was told by a mechanic that it might be the coil packs
They're $70 each..Is there anything I should check be fore I spend
the money?

 

I had coil pack #4 go bad on my '99 Expedition. The truck runs terrible and I was told will go into 'limp mode', shutting off the injector to the malfunctioning cylinder. When mine went bad, it happened after the truck sat outside for a few days. As I was told, the coils crack and get moisture in them which causes the misfire. One thing you might try is switching number 5 pack with another and see if the problem follows. I highly recommend purchasing a code reader if you intend on keeping the vehicle for a number of years. I got one for $150 a couple of years ago and it has paid for itself. I think the price has gone down to around $100 (check JCWhitney - Equus Brand part #zx274522) On the plug destruction issue, misfires can cause the electrode to melt. Is #5 the only one doing this? If so, then you may well have an injector problem. Swapping the coils should tell you if it is a coil issue or injector.

wczepl, on the 5.4, the heater hose leaks on the top of #4. I don't know why they had to use that crazy design, but it causes problems when they start leaking. Not sure if it affects #2 or #3, but if your vehicle sits outside overnight where you live, it is quite possible as moisture tends to get into any cracks you may have in those coils. As listed above, you might try switching one suspected coil with one you know is working to see if the problem follows before spending $140.

Hope this helps.
(I am not a mechanic, but I do all my own work so if any of this sounds wrong someone PLEASE correct me.)

 

Thanks for the info.
Ill try switching them around.
Auto parts guy said if they have white stains they could be cracked
and arcing out
I have the firing order, but do you know how the cylinders are
numbered on the engine. (dumb question)
Thanks

 

(rear of truck)

7 Motor 8
5 Motor 6
3 Motor 4
1 Motor 2

(front of truck)

 

by the way 7 & 8 are Fun to change out.....did I say Fun? I meant.... *%$%#! Time gets them though......so be glad that you don't have those to mess with right now....

 

SORRY....

Just saw you have a different motor....the order I sent was for the 4.6
I'm not sure if they are the same so check it out.

 

Passenger side from front of engine 1 2 3 4 driver side from front 5 6 7 8 so #5 is 1st one on drivers side

 

Here is the info on the 4.6 and 5.4 engines.

JMC

 

Thanks, guys...
Ill be working on it this weekend.
$50ea at Autozone?

 

Yes, and I stand corrected on the order.....what the hell was I thinking? Wifes car.??? The diagram is correct.... I just changed #1 on mine and I think it's was like 54 bucks at Autozone, they even include some silicone with them so make sure you put some in the boots to keep water and moisture out. Good luck