same ol same ol- 4.6 misfire
 

Hey newbie here with wore out eyes from reading past posts with no real conclusion. So HELP http://controlledlabsforum.com/image...s/banghead.gif

Here's the skinny-
Vehicle: 99 F150 2WD ext cab LWB 4.6 & manual. Current mileage: 143840. When purchased(Oct 03) it had an intermittent misfire. Shortly after I bought it(98k miles) I replaced the plugs(Autolite) & wires(Motorcraft) and fuel filter. Tested some of the easier things the Haynes manual suggested but found nothing. It ran good for a few weeks then began misfiring again. Ran some GM fuel injector/system cleaner & it ran normal for 2-3 weeks then back to missing again. The miss was only under load, never at idle. Got a code for the EGR once so replaced it. It still missed. I took off the top piece on the intake and cleaned the clogged EGR ports, this was late 2004. The engine mis-fired intermittently until recently when it gave a code P0350. It’s missing at idle etc and drinking gas. Replaced plugs again(Motorcraft SP432 Jan 08). Still misses at idle and under load constantly.

I'm wondering if I’ve clogged the cat running it this long with a mis-fire. Never thought of that. What to suspect? injectors? Coil pack? Is there a way to test the coil packs? I do not have COP.

Thanks, Dan

This code indicates a primary ignition coil malfunction which will cause misfires. Check both 3 wire coil connectors for proper fitting or damage. Make sure the pins in the connector are not spread from someone sticking a test lead in the connector.

I will check those connections. Does "primary ignition coil malfunction" mean that on is bad? I'm beginning to think chances are that one of these coils is bad. Is there a way to test them? I hate just throwing money and parts at a problem and crossing my fingers.

Thanks.

Yes a bad coil can cause this problem and this code.

hey man...im a newbie to...but i got a 97' with the same problem and i cant figure mine out either.Scanner says missing on #5 & 6. so i guess me and you are in the same boat...i changed plugs, coils, cut my cats off, used injector cleaner...and my eyes and wallet is hurtin to from this...i hope i can get it figured out...i will let you know if i do...

It sounds like you may have to conduct some of the tests the Hayens manual suggests doing. What plugs and wires did you go with. What about injectors. How frequently do these go bad?

I figure mine is either the coil or the wire or the injector.
It threw another code yesturday- P0305 Misfire No 5 cylinder. I figure I'll swap 2 plug wires and see if the misfire follows. If it doesn't follow the wire that'll mean it's either a bad injector or coil. . . I guessing.

I could swap coil packs too.

If you want to test injectors, buy an auto stethoscope and place at the body of each one. You will hear a loud clicking. No click - bad injector. FI going at 150k miles can happen.

Great idea. Thanks. Been using a wood dowl up to now to locate 'noises' in engines. Guess I'll have to actually buy a real steth now.

soudns like one of the coils to me - its been a while since Ive done this so I dont recogize the code but a reader should tell you which cylinder it is and that coil is probably bad. The are about $60 from Napa if I recall correctly. My 02 has been through three of them in 80K miles, so I keep one in the truck with the tools and the reader because a 4.6 doesnt pull well on 7 cylinders.

Alta, What type code reader do you use to show which coil is bad. I need to get one. Thanks, Carroll

Sounds like the coils to me also... FWIW it was very easy to change the coils on my '97. Look at the coils and follow the wires. If you have misfires on multiple cylinders and they are on the same coil then thats probably it.


Also, from what I've seen, clogged or inoperable EGR won't cause misfire or bad engine stumbling. I've run with the EGR vacuum line disconnected for months and never had a problem. When I fixed the problem the engine light went out but the truck ran just as good.

As far as detecting clogged CATs... from what I've seen... if the vehicle has clogged CATs it slowly start to lose power over a period of weeks or months and then all of a sudden the engine will start to misfire and run rough. If you drive it around like that until it gets good and warmed up, look under the vehicle. You may see the CATs glowing red hot like I did.

I dont recall the brand and model - I'll check later today, but it was the $60 one from Napa, light blue, came with some software, small hand held about 6" x 2.5" x 3/4" - that help?

Alta, something to look for. Thanks, Carroll

Thanks guys. I bought an auto stethoscope to listen to the missing clinders injector. They all seem to be clicking away. I swapped 2 plug wires (5 and 6) and though it still bucks and misses I can't get a code to come up. WTF! I hate when crap like this happens. Hopefully I'll get a code heading home tonight. If not I guess I'll just replace the coil pack and hope for the best. Hate tossing parts at a problem when I'm not even certain what's the matter. Keep you guys posted on what happens.:-X16

OK, been a couple days and still no code. Since it's not tossing a code and still missing intermitantly after swapping the 5 and 6 plug wires what could I do next to check things? Is there any merrit in me thinking the CAT could be clogged after driving a few years with a miss?