What can cause a miss at 5k?

[OrangeMustangGt]

my car developed a miss at 5k grand.....it feels like someone shuts the key off........But here is what gets me....it only does it in ND gear and not all the time, only when hot.


any ideas? I believe it is spark related because the wide band shows 10:1 a/f ratio and i cant hear any detonation....what do you think?

 

[Black95GTS]

What are your plugs gapped at?

What are you using for an ignition system?

Is it fine after 5K rpms or does it continue to miss after 5k as well? I'm assuming you meant to type 2nd gear... that is definately odd that the miss is specific to that gear.

Adam

 

[OrangeMustangGt]

yeah 2nd gear, and anywhere from 4,000-6,000 it misses hard.....just cuts out......and what has got me driven up a wall is it is just 2nd gear! i verified it 3 times....just 2nd. WTF? the engine dont know what gear it's in!

i am currently running 10lbs of boost and am using autolite 103's gapped at .040.

i wasent having problems untill today....

I have an all stock ignition system save for wires and msd blaster coil.....BUT i just went outside and ran the car in the dark, and i was able to see some blue arcing from the msd coil, and the "coil" part of it is loose from the metal base....like the epoxy came apart somehow.

I changed it out with a stock coil, and tommorow i'll see if still does it.

 

[68torinogt]

you need to upgrade ignition ill bet that will fix it

 

[Black95GTS]

yeah 2nd gear, and anywhere from 4,000-6,000 it misses hard.....just cuts out......and what has got me driven up a wall is it is just 2nd gear! i verified it 3 times....just 2nd. WTF? the engine dont know what gear it's in!

i am currently running 10lbs of boost and am using autolite 103's gapped at .040.

i wasent having problems untill today....

I have an all stock ignition system save for wires and msd blaster coil.....BUT i just went outside and ran the car in the dark, and i was able to see some blue arcing from the msd coil, and the "coil" part of it is loose from the metal base....like the epoxy came apart somehow.

I changed it out with a stock coil, and tommorow i'll see if still does it.

Don't worry about the blue glow, its common on all inductive devices. Unless you can actually see electricity arcing I wouldn't worry about it.

Here's a question... if you put the car in neutral and rev it up to 5K, does it still "miss"? It might be a transmission issue.

And with your twins setup, aren't you going like 90 mph in 3rd gear at 5k? How the heck are you testing this on cape cod roads? 4th gear above 5K in your car would be like 140!

Adam

 

[HISSIN50]

you need to upgrade ignition ill bet that will fix it

My first thought too - I'm surprised the stock ignition has held up good enough for you running that much boost.

When a TFI starts to poop itself, you can get a high RPM miss, especially when the motor (ergo TFI) is hot. But it'd hamper you at all times - that second gear thing is funky.

Good luck.

 

[OrangeMustangGt]

ok as a follow up, i found the issue. I has thought i had my boost controller set at 10 psi, but i was getting a boost spike in 2nd and it was at 15psi, which i guess is where my ignition can't handle it anymore.

I turned my boost controller down a bit, so now it reads a solid 10lbs in 2nd gear at 5k...my turbos are a bit small, so in 3rd at 5k it would only read 10lbs because that is there max airflow.....i guess in 2nd i wasent pulling 100% load so it allowed a bit more backpressure.....because im still running 3:73 gears.

No missing at all even with the stock coil, But i will now put my msd coil back on!

And with your twins setup, aren't you going like 90 mph in 3rd gear at 5k? How the heck are you testing this on cape cod roads? 4th gear above 5K in your car would be like 140!

This is true, i am probably going around 80-90.....but if i cop dident see it, i dident do it. Luckly my problem was in 2nd gear at 5k...easily testable on 40mph speed limit roads.

 

[68torinogt]

too much boost