2012Five0
Junior Member
2012 Mustang 5.0 183k - Engine failed at 103k (replaced with Ford racing short block) - CAI 92 tune
My buddy bought this new back in the day for 36k back in 2011. He needed money for a tax bill last year, so I took it off his hands. Car ran fine. Trouble shifting at high rpm, damn thing didn't want to shift at 6k, but other than that ran great. I've ran it maybe 3000 miles since last June. I'd more partial to challengers, but I couldn't say no to a great deal, 7500, and I've been pleasantly surprised by the Mustang. It's great.
But last summer, on a hot day, the car was running terrible. I thought the clutch was gone. Very hard to launch. That was the start of my misfire problems. I think it was a 300 random misfire. He'd kept up with the oil changes, but he hadn't replaced the spark plugs since the engine was rebuilt.
I replaced the spark plugs. Stock gap.
Idle was dancing around at stop lights. And then I was running high rpm one day on the back roads and I had misfires at high rpm. Felt all over the place. 303 and 305, cylinder 3 and cylinder 5 misfire.
I took it back to a stock tune and replaced the coils.
Idle still dancing around around. Not stalling. No problem getting going. But at part throttle, 3-4k, I was getting 300 random misfire. But I didn't feel a miss except at idle. MPG down.
I used the blue juice to test for a head gasket failure; it didn't turn yellow. I cleaned the MAF sensor. Seafoamed it. Ran some RP Max clean too.
Idle still dancing around.
I pulled and cleaned the throttle body. Ran RP injector cleaner through it twice.
Idle still dancing around. I can feel the miss. Power and reponse seem better after replacing plugs, coils and cleaning MAF and throttle body. MPG isn't as high as it was when I first got the car. Yesterday, I was running it in one gear going through some corners, letting the rpms control the speed some, maybe 3500-4500, and it throws 300, 303, 305 codes.
I'm currently running stock tune with 87 octane. Idle miss. Not running like a dog, but mpg and power aren't tip top. I can't feel or hear a miss at high rpms. But it's throwing codes regularly. It's been cold here, and it threw a temperature code, something about not getting up to temp fast enough. Been watching the gauge, seems fine, code hasn't come back.
What's my next step here?
My buddy bought this new back in the day for 36k back in 2011. He needed money for a tax bill last year, so I took it off his hands. Car ran fine. Trouble shifting at high rpm, damn thing didn't want to shift at 6k, but other than that ran great. I've ran it maybe 3000 miles since last June. I'd more partial to challengers, but I couldn't say no to a great deal, 7500, and I've been pleasantly surprised by the Mustang. It's great.
But last summer, on a hot day, the car was running terrible. I thought the clutch was gone. Very hard to launch. That was the start of my misfire problems. I think it was a 300 random misfire. He'd kept up with the oil changes, but he hadn't replaced the spark plugs since the engine was rebuilt.
I replaced the spark plugs. Stock gap.
Idle was dancing around at stop lights. And then I was running high rpm one day on the back roads and I had misfires at high rpm. Felt all over the place. 303 and 305, cylinder 3 and cylinder 5 misfire.
I took it back to a stock tune and replaced the coils.
Idle still dancing around around. Not stalling. No problem getting going. But at part throttle, 3-4k, I was getting 300 random misfire. But I didn't feel a miss except at idle. MPG down.
I used the blue juice to test for a head gasket failure; it didn't turn yellow. I cleaned the MAF sensor. Seafoamed it. Ran some RP Max clean too.
Idle still dancing around.
I pulled and cleaned the throttle body. Ran RP injector cleaner through it twice.
Idle still dancing around. I can feel the miss. Power and reponse seem better after replacing plugs, coils and cleaning MAF and throttle body. MPG isn't as high as it was when I first got the car. Yesterday, I was running it in one gear going through some corners, letting the rpms control the speed some, maybe 3500-4500, and it throws 300, 303, 305 codes.
I'm currently running stock tune with 87 octane. Idle miss. Not running like a dog, but mpg and power aren't tip top. I can't feel or hear a miss at high rpms. But it's throwing codes regularly. It's been cold here, and it threw a temperature code, something about not getting up to temp fast enough. Been watching the gauge, seems fine, code hasn't come back.
What's my next step here?
