Engine started running rough low rpms definetley has a miss. Higher rpms Idont notice it Ive drove it maybe 5-8 miles since this started no check engine light yet I was thinking a bad cop or plug. Any other Ideas this Is a 99 5.4 its been around 13,000 miles since I did plugs, fuel filter, any suggestion would be great.

 

Take your plugs out, if they have a bad fuel smell and/or are browned, replace them. That's usually the problem if your engine is missing. It could actually be a coil. My advice is to take it to a mechanic that you trust won't try to rip you off. It could be anything, but normally, an honest mechanic will figure it out, and won't rip you off, and just replace everything. BAD.

I hope you get it working.

Dan

 

If it was a coil or a plug wouldnt the check engine light trip on? I havent had the light come on yet thats why Im a bit confused

 

I took a look under the hood today noticed coolant on the cop near the firewall on right side so I took it out checked with my ohm meter nothing its dead put in a new one checked resistance first should work fine guess what still has a miss I still havent had a check engine light but I guess Ill check them all tonight and check plugs I just dont understand my idiot light not coming on for this ? any body had this before

 

Ok checked all the plugs checked all the cops checked the wiring connections all good still have a miss and still no cel light ! whats going on hear maybe a sensor somewhere but wouldnt that trigger the cel light? anybody have an answer or a guess?

 

i am having the same problem
new plugs, fuel filter, cleaned the Mass Air Flow sensor
if i am in park and hit the gas quick it misses if i run it up smooth to 1500rpms no miss as soon as i put it in drive it misses until i get going then seems fine until it shift or i give alot of gas seems like a under load problem i'm guessing


whats next lol
99 SC 5.4

 

Mine does it at start up at first it seemed only to do it lower rpms but its doing all the time I asssumed it was a plug or cop problem but no check light has me very confused anybody ou there had this and figured it out please drop me a line I really dont have the cheese to take it to the garage need help!

 

Did anybody figure out what was wrong? I just started having the same problem. Runs sluggish, idles poorly when put in gear and accelerating. No check engine light. I figure MAF would be a good place to start. Problem came up very suddenly. Checked wires going into coils, everything looks good there. Seems to run ok once I get up to speed, but it only started today. I figure it will get worse before it's over.

 

Exact same issue here. started this morning 03 5.4 litre - I have no idea - cleaned maf sensor, no help

 

hey temples,

I drove my truck home today, still having the problem. If this were a truck I bought 20 years ago, I'd say the fuel filter was going out. Not sure with all the dang electronics they put in these things today. Because I don't have a check engine light coming on I doubt it is a MAF, O2 or any other sensor. Might be a plug or a coil though. Don't know if coil paks throw a check engine light. I got a better feel for what mine is doing. It actually cranks and idles good, I get a slight dip in rpm's in idle occasionally but really I can't say the problem is with the idle. That makes me think there are no pcv leaks. I fixed my pcv lines about a month ago anyway. My understanding is Pcv leaks affect idle too so I'm pretty certain mine is not pcv related. The truck is real sluggish when I try to accelerate. No backfires, just hesitation when I try to accelerate. I drove it 45 miles to get home and it ran pretty well on the interstate once I got up to speed. I'm going to put a fuel filter in but I don't think it will be that simple. Gonna search the forum for some suggestions. I'll let you know what I did to fix mine, hope you will do the same.

clintc
99 F150 5.4L XLT Supercab

 

I got the exact same symptoms.. highway is fine.... occassional roughness at idle, but mostly in the 1-2k rpm range on take off or acceleration...

I even thought maybe bad gas or something. It just started this morning and I dont even have 60k miles on my truck yet.

I have to drive this damn thing 12 hours tomorrow (6 hrs each way) to pick up a motorcycle I bought in Toledo. I sure hope I make it - Either way, I think its going in the shop when I get back. Let me know what you find.

 

I drove about 11 hours yesterday and it got worse and worse. i had to drive with overdrive off (hilly terrain) to keep the rpms around 3k to avoid the roughness. Anyway - 150 miles into my trip, the check engine light starts dancing on my dash. When I read the codes, I finally got p0301 - cylinder 1 misfire. So when I got back, I replaced the ignition coil and spark plug. Funny enough ( not really ) - I still had the miss from driving it 2 blocks. So I gave up.

Then, this morning, I drove it to work (about 10 miles) and the issues slowly disappeared. Its running great now. I don't know if the computer had to learn something or what... Strange.

 

I guess I drive it till I get a cel or it goes dead. I wonder if a code will come up without the cel on. I changed one coil pack and plug last night, got dark and havn't done anything since. Guess I'll work on it over the weekend. What I don't understand is the symptoms. I would figure there would be backfire and a rough idle if a coil is bad. But, I'm basing that thought on how a distributor or plug wire would affect an old school motor. Until I saw your post today, I had convinced myself I had some bad gas. I even changed the filter earlier this evening and dropped a can of iso heet in the tank. Ran good for a half mile and it started acting up again. I guess the coil pack starts breaking down the hotter it gets. Anyway, I suppose I'll have this solved sometime Saturday when I get some time off. Thanks for letting me know what you did. That helps.

 

I ended up replacing all spark plugs tonight and the old plugs were pretty burnt up... I had 60k on the original non platinum motorcrafts... it runs even better than it did when I bought it 15k ago... it was definetly all in the plugs and the one bad coil.

Good luck

 

Temples,

The cel finally came on, I got a PO303, cylinder 3 misfire. Changed the COP and plug, cleared the code and it runs great again. I guess I'll change all the plugs today or tomorrow. I am not looking forward to cylinder 4 though. Anyway, I appreciate your feedback, it helped alot. I was convinced this was a fuel filter or injector problem since the idle was ok. Of course in the end, when the cel came on, the idle was getting bad too. Good learning experience, should be alot easier the next time a COP goes out.