its a 98 with a 4.6, k and n 77, hiflow maggie cats and flowmaster. i have repalced the coil packs, and put in motorcraft plugs and a new fuel filter. as well as an having edge evo on level 2.
i can not figure out why but it misfires bad at low rpms and shakes the truck around. it will be running ok but when i put it under a little load like going up a hill it starts to get real bad. i have played with the edge tuner, i threw it back to stock and it misfired worse, that's why i didn't put this in the tuner/chip forum. so i put it back on level 2 and retarded the timing a little and that seemed to help but it still misfires. i am also getting a little backfire action as well especially when i coast into an easy-pass lane and then go to re-accelerate after the toll. any help would be appreciated. its so annoying having it run so bad.

i pulled some codes and they were giving cyl misfire codes, a p1000 n p1500. even though i have not reset the system, clearing codes and stuff, for a few thousand miles.

any ideas to what could be causing this?

 

bump, could it be the k and n? i usually clean the MAF but maybe that got dirty and caused it to run crappy then messed up the cats? i cleaned the throttle body 15k ago, the egr i had to re-attatch to the exhaust manifold but its not leaking. anyone else with this? pulled a few plugs and they look pretty good...

 

bump

 

wires are how old? and what kind are they.

 

Get a scan done in mode6 to see what is really going on. Read O2 sensors, LTFT, and misfires can save you from throwing money at the problem.

 

the wires are less than a year old. not quite sure what kind, whatever Sanel sell. ill get it scanned by an actual code reader/puller and not my edge today but there is no CEL, unless it burnt out. ill also clean the maf sensor too. but it it can run fine driving through town and at low speeds but at 65-70around 1700 it skips and bucks just moving the truck along. at around 75-80 it runs a lot better but will have a harsh "hard" misfire that shakes the truck, but they are less often.

im going to do some searches on LTFT,

i also dont floor it, i try to keep it under 2k rpm as its getting older and i need it to last. but i had to the other day to get on the highway while not using an on ramp and not that it was fast before, the truck couldn't get out of its own way so why would it misfire under a load but then run alright in another situation?

 

If they are aftermarket wires, they are suspect. Did you use dielectric grease in the boots when you changed them and the plugs and the coil packs?

 

yes i did use the grease, i just took apart the throttle body, cleaned it , cleaned the egr ports they were not clogged cleaned what i think is the dfpe and cleaned the MAF sensor and cleaned the k and n filter. i am now waiting for it to dry in the sun. everything in the throttle body was pretty clean. so i dont think these were the problems. but i had time to do it with the air filter off which was dirty.

can the autozone or advanced auto tester test mode 6?

if it is the wires will the code puller be able to tell me. i dont have enough cash to throw parts at it till i fix it...

 

if you have multiple missfires there is a good chance its the wires. either that or you have a coil on its way out. Are the miss's on the same side? if they are it might be the coil for that side. If not go ahead and get a set of motorcraft wires. Get them at Rockauto.com. Think there about $70 from them VS $170 at the dealer..

 

make sure your wires are all the way on. i had a random mis-fire to after doing plugs come to find out some of them didnt seat all the way and i then got a bunch of grease havnt had that prob again.

also i used aftermarket wires they were a cheap 30 dollar brand only lasted 20K or so. motorcraft wires are 112 for a set of 8 but so worth it.

 

70 bucks at Rock Auto.

 

checking to see if the wires were seated was the first thing that i did, so it looks as if i will be visiting rock auto. numbers 1,3,2 and 5 have thrown misfire codes and i dont have my haynes with me to check the cylinder alignment which i do not know off of the top of my head. but ill look into that, i know that it is most certainly on this website a click away with the search button.

 

#1 is front plug passenger side, with 2, 3, and 4 going back. #5 is front plug driver's side, with 6, 7, and 8 going back.

Are you sure you have the coils and wires installed correctly? It will run if you have a coil reversed, but not well. This engine uses a waste spark system, but with opposite polarity.