Lean Misfire

[PBH]

My 2001 4.6 seems to have a misfire under light acceleration, I feel it on small inclines with the cruise engaged, and around town under light acceleration.

I have no fault light. I am thinking mass air or a bad spark plug. (The vehicle has 80,000 miles on the original plugs.) Any suggestions?

 

[monsta]

I'm thinking a bad COP. I think the dealer has the best tool to diagnosis those though.

 

[3rd7son]

I had similar problem for the last few months. Going up fairly steep inclines would cause sputtering/misfiring.

Local Ford dealer connected and analyzer and drove it around. Identifed COP #8. Changed it (and spark plug). Now runs fine.

Cost around $225.

Good luck.

 

[PBH]

Thanks. I knew it couldn't be cheap. It's much better in the warm weather, I'll have to do it in November. maybe my OBDII will show a misfire.

I can't even see the spark plugs, so I'm sure this won't be easy to fix myself.

 

[3rd7son]

Total cost was as follows:

$65 for analayzer.
$120 for COP.
$7 for plug.
$30 for labor.
(all approximate).

I have a buddy who could get a COP for around $60. The hard part is figuring out which cylinder. (Thus, the anaylzyer.)

Looks like a front one (COP and plug) would be pretty easy. COP is held by only a couple screws and boots over the plug.

#8 is in the back so I didn't want to mess around

 

[SONGDOC]

THANK YOU,
man i've been tracking this down for a while.
i've finally gotten the misfire on cylinder 8 code. should i go ahead and replace the COP while i replace plug. that thing is a ***** to get to for me.

 

[3rd7son]

If I recall corrrectly, they recommended changing the plug also (corroded due to mis-firing). If it's getting near your 60,000 mile tune-up you may want to change all of them right away.
Good luck

 

[SONGDOC]

yes, i am going to replace the plug. i need to know ,if it is worth the time saved, if i should replace the C.O.P. do they go bad often? is it worth the money now?
any help would be great. thanks in advance.

T.W.

 

[3rd7son]

Sorry for the confusion.

I assumed you were asking if, when changing the C.O.P., you should also change the plug (not visa versa). I would expect the misfire is due to a bad C.O.P.

Who is doing the work? I would expect a Ford dealership (or experienced Ford mechanic) would recommend the same. If neither, try calling a Ford dealership, tell them the situation (misfire) and ask what they would do?

Good Luck.

 

[stang99x]

I had this same problem on my navigator once. I just bought one new COP and 8 new plugs, and one at a time replaced the plugs with the new COP until I found the guilty party.

Total cost

COP from autozone $47
8 Doube platinum plugs -$32
My time screaming, yelling, and cussing, $priceless$