Misfire

[TimboSHO]

Misfire *Updated with Codes

I put new motorcraft wires in about 20K ago, and new motorcraft spark plugs about 10K miles ago. I noticed the problem about 1-2K ago and it hasn't really gotten any better or worse (except for one time it seemed like i was running on 5 cylinders constantly). It only misfires under load. I've checked and rechecked all of the plug wires and connections, spark plug gaps, connectors at the coil, etc. I've had a couple of ignition cycles where it seems to run just fine as well. Could this be my coil going bad, or is there anything else I can check? Any suggestions are appreciated. Thanks.

 

[Lorenr]

Read Your Codes

These are generally hard ones to figure out. Thats why the SHO is designed to set codes.

I'll bet at least one was set. Break them out and tell us what they are.

 

[TimboSHO]

Alright, I'll check the codes even though the light has never been on, but I had another idea. I've been running regular unleaded for quite some time now. Would that have anything to do with a misfire? I'll let you know what codes i get. Thanks.

 

[shofan33]

You can always follow the wires with a test light about a 1/4 " away from the wire at 2500 rpm and see if the wires got open somehow.

 

[1slickRED89]

I would check the resistance of the wires. make sure they are all the same.

i just ran into a situation where DIS was misfiring under load (in my case >30PSI boost) turned out one of the wires had 150Mohm resistance and was running out of available coil voltage. this, after trouble shooting EVERTHING else.

edit.done any work to the car or did this start all of a sudden?

 

[TimboSHO]

"Bump"

Wow, this was on the third page already!

Ok, since the last post my car actually died when I was getting on the on ramp of the highway. I went through first and second gear just fine, but when I tried third, it was like there was nothing there. I tried 4th and 5th and still nothing. I went back to second and it worked fine, and then the car just died. I tried restarting and it would crank (tach moving as well) but no start. I went under the hood and unplugged and plugged the coil pack back in, and tried again, and still nothing. So I sat there waiting and wondering what to do for a few minutes, and then it started back up.

So then I ran the codes after I got it back home. KOEO I get 11 twice, then it flashes once and I get 95 twice. The order of this confuses me some. KOER I get 13 and 73. I got 77 once, but I think I goosed it too soon. I also got 25 once. When I got the 73, I waited until after the RPMs came down and after the CEL blinked once. It always did a half of a blink after I did that too. I did the cylinder balence test and I got no problems.

I'm wondering since I have the 95 it might be why my car died on me the other day. But it doesn't relate to the other codes either..... and why would it have the 11 right before it with that space?

As far as the code 13 is concerned, I have had a couple of times where the car would idle high (1100). I would shut it off and turn it back on and the idle would be normal again (800). IIRC, this was before I noticed the misfire.

The 73 is confusing to me because I have no other symptoms that would point to the TPS. Maybe I'm not 'goosing' it at the correct time?

I'm sorry this is such a book, but I'm not the best at diagnosing ignitioin problems. I really appreciate it if you read it this far and have any ideas! Thank you so much.

 

[SHOblime]

Could this be the crank sensor?

 

[TimboSHO]

Ok, I understand why the KOEO codes were the way they were... the 95 was stored. So that's cool. The resisteance of all the wires was an equal amount per foot, but the number 3 plug had a bit of mud and/or rust (?) on the outside of it. All other plugs looked fine, although they have quite a bit of carbon on them (the last plugs didn't last that long either)....