I have a 99 F-150 w/ 5.4 w/ a mis-fire problem. I have 75000 miles so I went ahead and changed the plugs. That helped a lot but did not solve the problem. I pulled all of the coils and ohm'd them out according to the manual. I got close to the stated 5.5 ohms across the primary. On the secondary the published ohms is 5500. I got 5700 ohms above the rubber isolator. But I got 9000 ohms on the flat that touches the plug (below the isolator). I got this on every one of them. Is this normal? I think I have a coil problem but am not sure??

 

For the coil packs remember that heat will change resistance if their breaking down.
chk them after engine is hot, been running for awhile.

Or get the engine on a lab scope or a scanner capable of reading each cylinder misfire count!

Just my thoughts

Rich

 

I was having a similar problem of misfires. I certainly know a skip when one cylinder goes and it was nothing like that.
I decided to try something I have done with my fuel injected bike that worked. I ran it on an alcohol mixture. I poured approx 2 gallons of 99% isopropyl alcohol into 1/4 tank of gas and it cleared up the misfiring almost immediately. This is probably not a recommended repair but, it worked.

p.s. the performance has never been better, even after the alcohol was used up.

 

i own a 99 f-150. 4x4 5.4v8

there has been a coolant leak by cyl number 4. several times. i have personaly replace coil #4 5 times. and at 135K i just repplaced coil number 1. work was just done to the engine. so ill bet that someone cracked something they werent sposed to while putting the coilpack back on . but who knows. coil 4 and 1 are the only ones that i have ever had to repalce

 

Thanks for you comments.

I cleaned the fuel injectors early on thinking that could be part of the problem, but it wasn't. I have a code reader and the first code I got was a general misfire. After a few days the code went away (not the misfire). After a couple of weeks it started running really bad 1 day and I got another code. This code was a cylinder 8 misfire. The truck started running better (back to the usual misfireing) at the end of the day. After that I switched coil 8 w/coil 5 hoping to get a misfire on cylinder 5. I never did. Finally I took it to a shop to read the codes. They drove it and tried reading codes. They couldn't get it to read codes either and thought that I should be getting plenty of codes, by the way it was running. Anyway I finally changed coil #8 (now #5). The coil label on the new one was a little bit different again, so I guess it is a 3rd generation coil. Hopefully this one will last longer. It has been running great since then, although the last couple of days it seems sluggish again. I think the coils are breaking down (since I'm measuring higher resistance) and will probably have to replace all of them eventually.

 

watch out. if anyone knows where one can buy coils at a cheaper price other than from ford. that would be great. cause the price went up . at least in the area that i live in . before they were about 80.00 . now they charge almost 200. and installation is extra. i need to get a code reader so i dont get raped taking the truck to ford. can anyone recomend one.
thanks.
brant

 

I got my coils at O'reily (used to be HiLo), they were about $60.00. The code reader I got at Autozone for about $100.00. I forget the brand name, but it can read and clear codes.

 

thank you much sir... this forum helps alot of people ..

thanks again .
brant b