jflint

Truck: '98 f150, Triton 4.6 V8, 155K miles

On the way to drop my kids off this morning, the engine started missing. I took it by Advance Auto and their scanner said that cylinder 4 was misfiring. Cylinder 4 is the front plug in the passenger side. So i replaced the plug and plug wire on that cylinder and it is still missing.

I have not taken it back by to see if anything else shows up. Also, I put a longer plug wire on just to see if that is what it was before I dropped $50 on a whole new set of wires. Would have have anything to do with it?

The only other error that showed up was insufficient EGR flow, but that has been on there for a while now.

akdoggie

I may of read you wrong, but did you say it was the front plug on the passenger side? That is #1 not #4. You want the very back plug on the passenger side.

jflint

okay, i replaced all the plug wires this morning and took the truck for little drive. probably no more than 6 or 7 miles. just surface roads, so never really got higher than maybe 40mph.

Engine seemed to run fine until the last mile of the drive, then it started missing again.

Next step is to replace plugs (After getting the computer scanned again). Am I missing something though?

Even if it was a bad plug, would a new wire have let it run smooth for that long without it missing?

otto457

Yes it can run fine after a wire change until the PCM detects another misfire thrown. Good bet to change the plugs and go from there.

vfast

the egr flow issue..just pull it off and clean it mostly likely it's pluged or close to it...you will need an egr gasket about 3 bux

lovefx

I had this happen to my truck just last week. I replaced all 8 spark plugs and one coil and it fixed the problem. took my truck on a 100 mile trip today and worked great.

The Ford Kid

Just had this on my truck we figured it out after doing all sorts of test the fuel injector went bad and ran lean causing my plug to melt in the head

jflint

Just swapped out the plug in the #4 cylinder (man that is a tricky one) and apparently some oil had gotten into the plug well. Even though I swapped the wire, there was still some down in there, because the top side of the plug was dripping with it when I pulled it out. However, the bottom side of the plug was still in good shape (see image).



I dropped the new plug in anyway. I took it on about a 10 mile drive and everything seemed to run smooth, so I guess the case is closed on this one.

Up next is cleaning or replacing the EGR valve.

c9night

The plugs on this truck suck. I had my truck felt like it Ed misfiring for a couple of months took it to mechanic twice but no codes was showing up
So they said it was a vacuum leak. I replaces everything from sensors to hoses and nothing. Finally two weeks ago it through out a code and it was #3 was missing. It had burned off part of the plug. After 400 dollars it runs fine.

F150 Lee

My '99 4.6 started has a dead miss as of this morning after a friend borrowed it yesterday to tow a trailer a short distance. It has had an EGR code P and two P0000 for awhile but I rarely drive it and it hadn't seemed to affect how it ran.

Now it is a dead miss at all times from start and idle to driving. It is not throwing any additional codes like a cylinder misfire which might be helpful to track it down. I'd prefer to avoid just throwing a round of plugs and wires at it if possible. Any way to test the coils or any of this other stuff?