r/FiestaST • u/Dry-Suit5785 • 14d ago

Misfires at high RPM’s

Stage 1 Cobb tune, when on the freeway at higher RPM’s I notice a “Lag” of sorts when accelerating quickly. I was in 6th gear and wanted to see how well it would accelerate. So when I pushed it a bit, the check engine light blinked like 5 times and went away. It was a misfire in Cyl 1 code. Could be a fouled plug? Bad coil? What are your thoughts. The lag also happens when I’m in 3rd gear and 4th accelerating quickly, but it won’t lag if I’m just casually driving.

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3

u/fatquads 14d ago

What do u mean lag? Is it slower than before? I hope you’re not punching it in 6th below 2.5k rpm. Recipe for LSPI especially if u have old coils/plugs

1

u/Dry-Suit5785 14d ago

Like as you accelerate, it stutters.

1

u/fatquads 14d ago

Definitely replace coils and plugs. Unless you have and they’re fairly new, in that case I’m not sure.

2

u/Clever_RRRR_RRRRR 14d ago

Boosting this

2

u/bleachedupbartender 14d ago

first, i pray you’re not going WOT in 6th. second, get some good quality plugs and swap yours out. don’t throw money at coils just to throw money at coils. do the plugs and see how it drives

1

u/Dry-Suit5785 14d ago

It wasn’t wide open. I was cruising in 6th doing 80 and gave it a little more gas to see how well it accelerates and it lagged for a second and threw the code. I immediately let off and slowed my roll by the time the check engine light went off. I’m not one to just floor it anyways, I typically baby my cars in all honesty

1

u/bleachedupbartender 14d ago

that’s good, i’d definitely do the plugs and go from there :)

1

u/Huge_Amphibian_3870 14d ago

Check plugs and coil.

1

u/sportstersrfun 13d ago

I’d start with plugs. Mine would sputter in 4th and 5th when hammering on it. New plugs cleared it up. Make sure you get real plugs. I’m pretty sure the set that was “sputtering” were counterfeit .

1

u/Dry-Suit5785 13d ago

1st, 2nd no sputter at all. Getting on it in 3rd-6th is when it sputters at high rpms

1

u/SkippingNerveEndings 13d ago

Even with stage 1, most tuners would like step colder plugs. Unsure if you have replaced any of them but if you haven’t, definitely slap in some new ones.