Two5.0's

Has anyone had trouble with #8 cylinder spark plug going on their cars with no tuners? My Mustang GT is only two years old with 10,300 miles on it and it started jerking and hesitating. Took it to Ford and was told about #8 cylinder. I only have Borla pipes and catbacks on it now and a CAI. Was going to get a tuner and a bigger throttle body until this happened. Now I am scared to add the mods because this happening. Mentioned to my mechanic about putting on a bigger throttle body and he said no matter what you need a tuner to get the performance out of it, but then he goes, then Ford frowns on that (tuner and warranty). What to do!

dcarlinf1

The CAI without a tune could be the cause. Probably was running too lean. But, what do I know? I am not a mechanic. Good luck, I hope it's minor.

huntiez

o i hope u dont have a number 8 issue

scottmach

Stock untuned cars have had #8 cylinder issues. It's actually a flaw in the stock tune. If your CAI was a no tune CAI that isn't the problem other than you wasted money on it. Just like a different throttle body is a waste of money. Yes a tune will void your drivetrain warranty.

Two5.0's

Yes, the mechanic said it was running to lean. He said to get the tuner because of the modular motorsport racing CAI and Borla catbacks. The #8 was effected, just the plug went bad. Misfiring. He is a really good guy and did it under warranty since I only have 10,500 miles on the car. He told me to get the BBK 85 mm throttle body later. I don't race it, just want some more horsepower because of the newer ones have more than the 2012 and see if I can get a bit better gas mileage, when I keep my foot out of it. Thanks.

Nuke

The catbacks don't require a tune. The TB is useless w/o other supporting mods. You might or might not get better gas mileage with a tune but even if you do get a gain it'll be minor and the break-even point between fuel savings and the cost of the tunes will likely be a few years. Regardless, a tune is worth it for the performance gains, period.

Two5.0's

Well, the catbacks were an issue though and the CAI. When he did the diagnositics on my car, it showed 11 misfirings with the #8 cylinder and it also showed the modifications.... My mechanic told me to get the tune because I will continue having the problems otherwise. Under Ford TSB 11-7-7 he could of said he could not warranty, but since I am a female and honest with him he fixed it. If he says to get the tune, I am getting the tune for street and performance. Thanks for your input!

scottmach

Your mechanic clearly has no clue and is steering you in the wrong direction. The catback could not have caused any problems regarding the misfires. The CAI is debatable. But if you're having problems now DO NOT TUNE IT! You run the risk of some major financial future problems. Is your mechanic a Ford tech working for a Ford dealer?

Deranged2013

I would ask your mechanic to check compression on all your cylinders before you decide to get your car tuned. Don't just buy a random mail order tune. Go with a tuner that request to see data-logs on your car before changing any parameters. This way he can see if everything is working properly and if your car is safe to tune. RESEARCH before you mod! Good luck!

Two5.0's

Since my car is under warranty I went to our local Ford dealership where I have taken five of our Fords and ask for the same Tech all the time. I was was right there with him when he pulled up on the computer the diagnostics on it and again, it said modifications. He did a compression check on the cylinders and did another one on #8 when he was done working on it. Just got off the phone with him about this to make sure AGAIN. He said he has seen this with three other vehicles lately and yes, mostly it was the CAI to lean with air pressure and the computer gets confused basically and it misfires he said. I also talked to another local dealer south of us, David Ragan the NASCAR driver owns and they said the same thing.
By the way, even though I appreciate your input, are you a mechanic?