Need some help. 1997 F150, 4.6L - just over 200K miles. Shut off the truck one night (it's been running fine). Started it up the next morning and it ran like crap. Drove to work and the CEL was blinking and then came on solid. Had the code scanned and it tells me there is a misfire on the #4 cylinder. The wires are about a year old. Plugs pretty new. Now, i know they can go bad sooner than that, but what is the % chance i have a bad coil pack? I'm a cheapskate trying to avoid going to the shop and avoid $85/labor hour. What should i start with? coil pack, wires, ?

 

I would start with new plugs and wires. When the CEL is "BLINKING" it means misfire. I get about 60k miles out of them in my 4.6. Motorcraft that is, and, that is all mine will run on.

As for the coil packs, I'd say the percentage is low it is the cause, BUT, don't rule it out yet.

I would give it a tune up and see if your code goes away along with the miss.

 

pull cyl 4 plug and wire look at the wire and plug make sure there is no water any were around it. have you ever replaced the coil packs?? what kind of plugs do you have in there? my CEL has been blinking plenty of times. its your O2 senors telling the computer there is fuel in the exhuast pipe and that its misfiring. will also lead to a pretty cool backfire out of the cats or the end of the pipe its a pretty cool noise. but not the best for your truck. ive had my truck on 5 cyl's before but id say to start with pulling the wireing and plug and inspecting everything.

 

Follow the number 4 wire back to the coil pack. Pull the wire from there, you should get a shock (small). To check pull a wire from a different plug. The engine running will change when it loses a spark.

When I had this on #5 the coil pack tested fine on the bench but would not fire when on the truck. I pulled wire #5 and nothing, Pulled one wire next to it and sparks were dancing.

New PEPBOYS pack for $50 and runs great.

 

No, i've never replaced the coil packs. This engine has just over 200k on it and up until now has run better than anything i've ever owned before. I've been amazed at how well this engine ran with that kind of miles. It's had the standard maintenance type stuff done, and at about 150K started having EGR trouble that i have to work on about once a year (cleaning out the throttle body). But no new coil packs.

 

My coil pack started crapping out at 82k, I'd say it's quite likely yours is starting to go. If you want to test without buying anything, I think you could swap yours from one side to the other and see if the misfiring cylinder follows. You should go get some dielectric grease and clean/reapply if you do this.

 

Sounds like you took care of the truck in the past and it has returned the favor with 200,000 miles on the clock. I think it's earned a new set of packs myself..

 

Cleaned out the plug wire, there was a little moisture around it. Reapplied some dielectric grease. Fired it up and it seemed to run smooth, thought i got lucky. BUT - as luck would have it, as soon as i headed down the road it started missing again. So i'm gonna try the coil packs. Question - do those wear out with use or are they good one day, and bad the next. It seems like since it's an electrical part there would be no 'wear' to it, but i'm curious if maybe the get weaker with age/miles?

 

They do get weaker with age. They may "WORK", but, not giving the required amount of fire to the plug.

I got 2 DURALAST packs for mine for 90 bucks.

 

My cel says misfire on number 3. Dumb question, is number 3 cylinder the 2nd one back on the left side?

 

3rd one back. Firing order -

4 8
3 7
2 6
1 5

Front facing down, #3 is on the passenger side

 

Nope, 3rd back on the passenger side.

V8:

4 8
3 7
2 6
1 5
Front

V6:

3 6
2 5
1 4
Front

 

 

Thanks to both of you. The last time I had a misfire it was a coil pack. I will try another one for this. I am too cheap to do them all at once, thought I probably should. The truck has 197,000 on it now.

Thanks again.

 

Well I have had a misfire on #4, so I changed the plug,wires and coil pack.Well when I started he up, did not have the fuel rail seated correct dome fuel on the #4 wire/boot, Took apart and cleaned it all, put back together and ran great for about 2 weeks.Well CEL came on again, misfire on 4.Well I smelled some anti-freeze the other day, when the misfire started, and sure enough boot was wet again with anti-freeze.Did some research and there is a Ford Service Bulletion out about loose heat hose clamps above #4 cylinder that are dripping anti-freeze and the #4 plug wire and causeing misfires on #4, so check or just tighten your heater hose clamps about that cylinder