1998 Ford F150 v6 4.2 I had a check engine light come on ran codes and it was a cylinder misfire. I bought new plugs and wires and once i got to the last plug i noticed it was disconnected so i plugged it back in and the check engine light went off. I continued replacing the last plug and wire. Now still no check engine light. idle is normal, but around 20 mph the engine shakes pretty bad. ive check the firing order multiple times reused the old wiress. i have yet to pull the new plugs and re use old ones. im stumped. note that it was running fine before the light and even when the light turned on. Please help. any insight will be appreciated thank you

 

re-check your firing order and make sure it is correct, even if you have, one more time. firing order should be 1,4,2,5,3,6. https://www.f150online.com/forums/19...ing-rough.html



It might be that you have another issue, a bad new wire or spark plug, (even if they are new)?? maybe a bad motor mount?? maybe a vacuum leak?? plugged fuel filter?? Too high of fuel pressure, ( bad fuel pressure regulator)???

Have you scanned for codes? Does it run better or worse, or the same if your drive over 20 mph??

 

I would double check the firing order. I've replaced my plugs in my 4.2 a couple years ago. I did one cylinder at a time, just to avoid messing up the order. No issues.

What kind of plugs are you using? Motorcrafts work best in this engine, and so do the wires.

Also, the 1997-1998 M/Y have issues with leaking intake manifolds which get coolant into the cylinders causing all kinds of weird things, including hydrolock. I betcha coolant is getting into a cylinder and it's trying to burn it, which water doesn't burn and it may cause a misfire condition.

How many miles are on the engine?

 

200000 miles. It was running perfectly fine before I changed out everything. I did each of them one by one. I am using bosch double platinum plugs.

 

Funny thing is I unplugged cylinder 2 and it alot smoother with it off.

 

Let me make sure I'm understanding this correctly

Cylinders on motor

firewall
3 6
2 5
1 4
front of truck

Connection on Coilpack

firewall
Plugs into cylinder 3 4 plugs into cylinder 6
Plugs into cylinder 2 6 plugs into cylinder 5
Plugs into cylinder 1 5 plugs into cylinder 4
front of truck

is this correct ?

 

BIG mistake. Get them out of there and put Motorcrafts in.

Check your coil pack for cracks and carbon tracks.

 

Solved. Thanks for the help everyone. I ended up pulling all the plugs and cyLinder 3 plug was cracked.

 

Solved. Ended up pulling all the plugs and cylinder 3 had a cracked plug

 

OK. I would still recommend replacing the plugs with MC.