When I pulled into my garage tonight with the window down, I noticed a very minor random misfire between 1,000 and 3000 RPM in neutral. I could both feel it and hear it in the exhaust note. It seems to be worse at 1500 RPM but in this case it might be a vibration rather than a misfire, hard to tell. From some older threads I found on the 4.6, the 1500 RPM issue seemed common.

Under load the car seems to run great at any RPM.

The car has a little over 1000 miles on it. I am not sure whether or not it has always done this or if this is normal for the 5.0. Has anybody noticed anything similar?

 

I think its only the air conditioner compressor kicking on and off. Turn your air conditioner off and see if it still happens.

 

Thanks for the reply. The AC was off, so unfortunately it isn't that. In any event, when it occurs it does so at a much higher rate than the AC compressor cycles. As I implied it is very subtle, so much so that I doubt I would notice it if the car was in motion, which is the real concern. It is most obvious in the garage when the exhaust noise is loudest.

I remember very early on (around March) one of the alleged reasons for the holds was a misfire in the 5.0.

I brought the car into the dealer to have it checked this morning. I'll let everyone know what they find, if anything.

 

Are you sure its a misfire and not just the computer adjusting trim? It could also be a detonation which would be much worse.

I would get yourself a data logger, these motors keep track of misfires and you can query it with ODBII.

If you are planning on tuning it, just get the SCT X3 now and use that as your data logger.

 

Just brought the car back from the dealer. They found nothing and presented me special service message 21441 which states:

"Some 2011 Mustangs equipped with 5.0L engines may exhibit some engine roughness at idle through 2000 RPM. This condition is attributed to high compression, high horsepower design intent performance characteristics. The IDS misfire test/misfire monitor may indicate a misfire event during these operating conditions. If vehicle does not display a malfunction indicator light or diagnostic trouble codes stored in PCM memory do not attempt repairs. If vehicle has misfire diagnostic trouble codes follow normal procedure pin point test. This condition will not affect engine or vehicle durability."

 

Ralph,
What ever came of the low rpm missfire issue? My 11' gtcs is doing exactly the same thing. Dealer didnt mention the "service letter" but since the ecu doesn't have any codes they are at a loss.
Mine is very sutle but noticible at 1300 and 2300 rpm+-. The dealer agrees its there but since Ford says unless there's a code there is nothing to be done.

 

My '14 does it and I figured it was just like that service notice says, and of course when you stick your foot in it it's all over then.

 

Hi Ltngdrvr
You're right when you put your foot in it its all over. Just disappointed Ford hasn't done something about it in the last 3 years.

 

^ but it's not broke....can't fix what's not broke.

 

Its not the radiator fan coming on is it? My winter car is a 4 banger and its more noticeable but after figuring that out I also feel it lightly on my V8 when the fan comes on.

 

Charliehorse
Nice website, I grew up in Oregon, been to all those spots over the years.
Ran the Shasta I5 Raceway last year South to North in my gtcs, usually though I run it in an F350 6.0, not quite the same in the truck but still fun.
We spend 4 days at Indian Mary's on the Rogue rafting each year really enjoy that area too.
The miss is I guess more of a vibration at about 1350 and 2300, I notice it driving because 2300 is about where I cruise.
The dealer I took it to agrees the miss is there but they dont know what to do about. They actually suggested I put an aftermarket tune on it.
I talked to another dealer this morning but now it seems Ford has decided i'm 2 months out of warrentee so maybe it is time for a tune.
Guess Bucko may be right, cant fix what ain't broke.