Can someone double check my logic?

[AutoHow.TV]

The classic misfire situation...light on all the time, blinks if I am driving around for an extended period of time: codes P0316 and P0301 -02 and -08

I am getting suspiciously great gas mileage so i am thinking it's fuel related--aka running lean. In fact, everytime the SES light blinks my A/F gauge reads very lean for exactly 25 seconds. It would be pretty unusual to see three spark plugs/COP act up right?

Car has 41k, original fuel filter, plugs, etc.

I did a search but not too many posts mention misfiring under 1000 rpms or misfiring and still getting great gas mileage!

Thanks

 

[KenB]

The classic misfire situation...light on all the time, blinks if I am driving around for an extended period of time: codes P0316 and P0301 -02 and -08

I am getting suspiciously great gas mileage so i am thinking it's fuel related--aka running lean. In fact, everytime the SES light blinks my A/F gauge reads very lean for exactly 25 seconds. It would be pretty unusual to see three spark plugs/COP act up right?

Car has 41k, original fuel filter, plugs, etc.

I did a search but not too many posts mention misfiring under 1000 rpms or misfiring and still getting great gas mileage!

Thanks

No, you're on the wrong track. Misfire codes will only be thrown if you are not getting spark.

How long have you had the pullies on? That would be my guess. Are they piggy back pullies?

 

[MyEarsHurt]

the ses light means its misfiring, the blinking ses light means it is misfiring more than 2% of the time (close to that at least). My stang was doing this last year and I replaced the fuel filter, spark plug wires, spark plugs, and it was cured...my car had about 50k miles on it when that happened to me. Try replacing the plugs and wires see if it helps...

 

[AutoHow.TV]

Thanks for the input...it threw a misfire code in the summer and it just came back so maybe it's gotten slightly worse (aka more plugs have gone) and that's enough to make the SES blink. I might be gettin better mpg on the highway cause the PCM keeps disabling my fuel injectors--lol.

Anyways, I'll throw a new FF, plugs and rotate the coil packs around to see if the code moves with them.

The pullies have been on there since before I purchased the car (I will def keep that in mind though).

 

[04GT]

I had similar problem and it was the fuel pump. Gas mileage went down 2-3 mpg after it was fixed.

 

[AutoHow.TV]

How did you know it was the fuel pump?

 

[04GT]

How did you know it was the fuel pump?

After trying to diagnose the problem for weeks and weeks by myself (with Stangnet help), I took it to a Mustang speed shop. They hooked up some kind of tester on the fuel rail and ran it on the dyno.

Coincidentally, my car had about 40K miles on it at the time.

 

[AutoHow.TV]

So I took into to the local speed shop and they pulled the codes (only 2 and 8 showed up this time)...turns out #2 COP was a little lose, but 8 checked out fine. So they moved #8 COP to #7 and told me to see if I got the code again.

Sure enough I did...and on the same two cylinders...2 and 8. I might attempt the fuel filter and plugs today since I have time

 

[04GT]

When mine was misfiring, I get getting a code on cylinder #1. Replaced plugs and one of the COPs. Those things are expensive!

 

[98stangv8]

I had the same thing not too long ago...I looked at my coil packs, and 2 of them had some burnout inside...replaced those and it is working fine...

 

[AutoHow.TV]

Replaced fuel filter and spark plugs over the weekend. Used autolites and made every effort to do a good job (dielectric grease, silicone spray). Car runs incredibly smooth and strong now. But the SES still came back...same two cylinders again.

I am starting to think it is the pullies or something mechanical, timing-related as KenB said originally. I have the piggy back pullies that were on the car when i got it. Anything I can check?

I have a little carchip that pulls codes and logs data every 5 seconds. I have been noticing that the data shows timing retards every now and then...

Suggestions appreciated!

 

[AutoHow.TV]

--

 

[AutoHow.TV]

I've since educated myself on the piggyback pullies that came with my car. Took it over to EB3 Motorsports here in Chantilly and told them I thought the pullies could be throwing the codes.

I worked with their tech, Jon: separated the aluminum and balancer pullies, reassembled and then retorqued the crankshaft bolt using the four step procedure.

Light came back at first but I disconnected the battery for thirty seconds and it's been fine for the past week...

Thanks to KenB for calling this problem out from the very beginning :SNSign:

 

[AutoHow.TV]

Talk about thread revival...I started this thing way back when I was still new to the whole Mustang thing...haha

Wanted to post for any one else that may come across this thread in the future:

The piggy-back pullies continued to act up over the past couple years. I finally bought new Steeda ones and installed them. I even filmed the whole thing which can be seen here on Stangnet's video section (under How-to)

 

[twogts4us]

Car has 41k, original fuel filter

Fix this quickly...it's cheap and easy.