Traded in my base Race Red Ecoboost for a base Ruby Red GT.
Has anyone else had this issue?:
On the test drive of the GT I thought I felt some random "dead spots" in low rpm, low/medium to high load.
I chalked it up to the water on the road creating resistance and slowing my momentum.
I decide to trade and get the GT. It had 150 miles on it. I've turned the odometer to 320 since.
When test driving the GT, the gas tank was about half full. Not sure of what octane, brand, or freshness though.
I told the salesman to fill it up with 93 or not at all. Off he went and filled up with 93, or so he said. I have no reason to doubt him, he's a nice guy who sold me my Ecoboost, as well.
Anyway, I drive it to work directly from the lot after signing paperwork. It's still raining like crazy and the dead spots are still there but there were tons of puddles to help the dead spots feel like water resistance. Same thing on the way home.
The next morning it's dry. I head to work and feel even worse dead spots. low/medium load to high load, basically all through the power band.
One day later I hookup my HPTUNERS scanner and confirmed the dead spots are indeed knock retard. Massive amounts. the more load the worse it is. Like 10 degrees knock retard in 6th gear at a mediumish load. Every gear is like that, though depending on the load. Even light throttle in 2nd going up a small hill.
6th gear feels like a turd. Almost like the car is going backwards. My old ecoboost would smoke this thing in 5th and 6th.
I run down to a half a tank and throw more 93 in from QT. Take it for a drive to mix up the gas good and the same thing is present... tons of KR and dead spots... which correlate to each other. As soon as I feel the dead spot I see the scanner shows KR.
I've driven cars that require
Premium fuel with regular fuel in them and they never acted like this. Usually the computer would use an algorithm and use a blend of spark tables when it thinks low octane fuel is being used. Driving should be seemless, but maybe a little less power than if you were running premium.
The car is not suppose to run ok, then dead spot, run ok, dead spot, dead spots and KR climbs as load climbs, etc.
Now, I'm new to the coyote engine and even newer to this new ecu they have in the MY15 Mustang GT. I come from the LSX GM side. I traded my C6 for an ecoboost, then the Ecoboost for the GT. My Ecoboost ran 87 just fine, by the way. I miss it in a way, but I can tell that this GT could probably almost hang with my old C6 Vette if it wasn't for this KR.
Anyway, if using anything but premium will cause this issue, then it makes sense that the half tank of fuel when I was test driving was 87 and my salesman could have accidentally put 87 in again.
But after me running it down half a tank and topping off with 93, I should have noticed at least a little less KR. I'm not, though.
I talked to my salesman today and he told me to drive it for a few more days, fill the whole tank with 93, and return for service if the car is still doing the same thing.
I do a long test drive and run my scanner before I buy a used car. I should have done so with this car before I bought it. Frustrated! Never thought about scanning a new car's parameters during a test drive before this. Stupid me.
I can post hp tuners logs later, or convert the logs to .csv and post.
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Originally Posted by txcharlie
