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Discussion Starter #1
So I purchased my ST July 23, 2016 with 20 miles on it. The dealer filled it with 87, ran that down and have been using BP 93 ever since. At about 980 miles i started feeling a slight misfire. After that one time, I didn't feel it again for 4 days. That 4th day at 1000 miles, the misfire was so bad I could hardly drive it and a CEL came on. Took it to nearby AutoZone to do a quick scan and it had 2 codes, P0304 and P0204, Cyl 4 misfire and Cyl 4 Injector Circuit. I immediatly thought bad injector or harness. I took it to Ford the next day and they said it was a bad injector. Ford replaced the injector and I got the car back in a day. No CEL and drove great. Now 2 weeks later, at 1230 miles, I am getting the same misfire feeling again, this time only in right turns on accel.

I always wait until the oil temp is at operating temp before boosting. I don't let my fuel tank get below 1/4 tank. This misfire only happens at operating temp. The car is stock, nothing done to it. I intend to do some mods but not while the car is acting like this. I understand I am still under warranty, but not knowing what could possibly be wrong is bugging me.

I was wondering if anyone had any ideas what could be wrong or what to do. Any additional info you may need, let me know. Thank you for any help!
 

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Same codes and same cylinder? If it is different cylinder you might just be experiencing a bad batch of injectors. Get the codes and cylinder affected and take it from there.
 

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I'm not sure is same codes or same cyl. There is no CEL. Do you think there could be pending codes?
Go have Autozone pull codes. They wont do more than give you a funny look, did it myself the other day and found a p0034 code. fuse was indeed blown.
 

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Discussion Starter #5
I took it to AuoZone, there were no codes. On my way back to work from there, the car was warmed up and I could feel the miss slightly on one right turn, after that, it was smooth.
 

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I took it to AuoZone, there were no codes. On my way back to work from there, the car was warmed up and I could feel the miss slightly on one right turn, after that, it was smooth.
Maybe your butt dyno is a bit off, i.e. it might be in your imagination since you had an issue previously. Keep an eye on it.
 

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Discussion Starter #7
Maybe your butt dyno is a bit off, i.e. it might be in your imagination since you had an issue previously. Keep an eye on it.
You could be right. I said the same thing to my buddy. I hope that's all it is. Only time will tell now.
 

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If you have a smart phone, I highly recommend getting a bluetooth OBD2 reader. Not only can it read and clear codes, but you can monitor sensors and parameters as the ECU sees them. I think the unit is about $15 and the app is about the same or so. Was really helpful when my SE went into limp mode a distance from home and freaked me out (was for the HPFP. I ended up just disconnecting the HPFP sensor and reconnecting it, then clearing the code, which fixed the issue). Beyond that, the car was dead reliable, so I used it to amuse myself by monitoring the engine or to check and clear the numerous codes of my ex's POS Escape.
 

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I took it to AuoZone, there were no codes. On my way back to work from there, the car was warmed up and I could feel the miss slightly on one right turn, after that, it was smooth.
Do you have the "safety nannies" turned off? Maybe you're making the TC kick in and that's killing your power. If it doesn't do it in a straight line I wouldn't worry about it.
 

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Discussion Starter #10
Check engine flashed today after short highway drive. It has the same 2 codes. P0204 and P0304. I'm taking it to ford on Monday. The light turned off after I drove home and went to my sisters as it's the only vehicle I have to drive. Now it's smooth again with no light. It's only been 480 miles since the injector 4 replacement. Makes me think the harness could be the problem. Just thought I'd give the update on this issue.
 
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