mongooztt

I purchased my 2012 Mustang GT 6mt-Brembo from Town & Country Ford in Bessemer, AL on May 5, 2012 with 35 miles on the odo (30 of those miles were from my test drive). On Tuesday May 8, the check engine light flashed 15-20 times under normal acceleration in 3rd gear and then went off. I noted this and went on. Thursday May 10 the same event happened under the same conditions but this time the light stayed on! I had advance auto check the code on Friday morning and it gave P0304 - #4 cyl misfire. I immediately drove back to T&C Ford and told them what happened:

Friday May 11 - They took the car back and I waited on it. 20 minutes later they called me up and said it was fixed. They performed a neutral position reset of the misfire monitor:

"351 start up IDS, run koeo Pass-P0304, koer pass, power balance test, roadtest with IDS monitor, reset misfire monitor neutral profile, retest ok"

All was good and I was happy until later the same day the light flashed 15-20 times again but this time it pulled power out of the engine big time and acceleration was cut in half. After restarting the car it was back to normal.

This is not a daily driver and the next time I drove the car was Wed. May 16. The CEL flashed again 15-20 times and stayed on. I did not drive again until I could take it back to the dealer.

Friday May 18 - I took the car to Townsend Ford in Tuscaloosa, AL (where I live). They pulled a misfire code on 2 cylinders P0302 & P0304. The coilpacks checked out and they replaced two spark plugs. The Service manager said they could not find out what was wrong with it and the Ford tech hotline told them to reset the computer. They did this 4 times before they could not reproduce the light. They left the case open and said if the light comes back on, take it back to Town and Country and they'd fax the service report up there on Monday. Low and behold The light flashed 15 -20 times and stayed on again not one hour after I picked it up from the dealer.

Saturday May 19 - I took the car back to Town and Country Ford, they had it for approx. 1/2hour and told me it was misfiring again but they didn't know why and if it does it again to bring it back on Monday. I told them I would drive out of the parking lot reproduce the CEL and bring it right back.

T&C had the car all day Monday and Tuesday and I picked it up this afternoon. They said they reset the misfire monitor profile to 6000 rpm:

"598 roadtest for engine miss, start up IDS, run koeo pass-P0300-P0301-P0307-P0308-P0316, DCL test, roadtest with IDS monitor, R & R all coils and plugs & inspect, contact tech hotline, reset misfire monitor profile to 6000 rpm as per hotline roadtest 30 miles to verify, retest P1000-P1000 464"

I'm concerned they just put a bandaid on by resetting the misfire monitor profile to a higher rpm? Has anyone else heard of this or had it performed? I told the service manager "what happens if I take it above 6000 and it happens again?" He said I should never have it that high and the engine will go into failsafe mode, log the rpm, and we couldn't warranty the work. I told him that was BS and the engine is designed to rev to 7k and more, it even has a factory shift light! He said you should never drive these cars like that...with a 2012 boss 302 parked not more than 10 feet from us!

The car now has 700 miles on the odometer, 300 of which have been put on after 3 visits to the dealer. I have babied this car for the first 500 miles and have only surpassed 5k rpm on a few occasions and by no means have I been "thrashing" the car. I am at a loss as what I should do. 3 visits at 2 dealers and no one can find out what is wrong with my car. I've done a little research on this forum and others and have seen where sometimes the only cure has come from replacing the crank sensor and some cases the ECU!

The car is "fixed" for now, but what happens after break in and I want to shift out at redline and start getting codes again?

97GT12

http://www.motorcraftservice.com/vdi...&menuIndex1=15

Specifically: http://www.motorcraftservice.com/vdi.../OBDSM1202.pdf

Page 16 starts the description of the misfire monitor.

I don't think they disabled the misfire monitor below 6000 rpm. They've changed the calculation and/or learning method somehow. It doesn't appear to have any sort of threshold of operation.

P0316 (misfire during first 1,000 revs after start-up) Shows that it is clearly has nothing to do with your driving. Could be the learning sequence of the monitor rather than real misfires.

The change in RPM for learning mode is 600, it might be a typo on the report. Or they expanded the learning mode maximum from 3700 to 6000 rpm. It's hard to figure out what they've done. But I see no capacity to turn off the monitor below a certain rpm. Only to effect the learning.

Also if they did up the rpm of it being active they've run afoul of the feds emission requirements.

My guess is there is something off with the crank sensor. They are trying to allow the computer to deal with it. Plugs etc replaced in case it was a real misfire condition.

mongooztt

Thanks 97GT12! Your reply puts my mind at ease. I think that maybe the svc mgr just didnt know how to explain to me what exactly the tech did and gave it his best. The car is running great so far and I have about another 80miles with no issues! I just wonder why the tech line told them to do this instead of performing a crank relearn or even replacing the crank sensor?

kritiana99

It's an interesting approach. I commonly see unexceptional views on the subject but yours it's written in a pretty unusual fashion. Surely, I will revisit your website for additional info.

FordService

Glad to learn all is good now, mongooztt. Please PM me if this happens again so I can escalate it.

Deysha

97GT12

np... since I have a '12 as well it's no wasted reading on my part. I'm just happy ford puts those documents out. they've helped me a few times over the years.