it never happend befor till tonight. i had 4 people in the car going about 60mph. droped to 4th gear and the car took off then bucked then took off again. it only happened 1 time. what could this be. it never happens when im by my self. thanks

 

you hit "fat" cut. too much weight in the car

 

lol.

 

Have you checked your spark plugs lately?

 

never. i just broke 30k.

 

loolx3123124

 

anyone??????????

 

What RPMs were you at? Do you have a boost controller? If it bucked really hard, maybe you hit boost cut off. RPM fuel cut will only make a horrible noise, not give you a huge buck.

 

hum. no noise. just a buck and id say around 5000 rpm maby a lil more. is this bad. and yes i have a mbc. set at 20psi. but never happend when im by my self. just when i had 4 people in the car.

 

Sounds like you hit boost cut. My car bucked super bad when I spike 25 PSI with my MBC. Having multiple people in your car shouldn't be a factor, its just embarrasing. What brand MBC?

 

forge unos. but i had no spike. it gos to 20 psi and dosent move.

 

Weird. I have an UNOS and was having all sort of spiking issues in the beginning. So with your friends in the car, you droped to fourth, going about 60, and you are positive you were looking at your boost gauge and saw it hit 20 and no higher? It really sounds like you hit boost cut, and that jerky sensation is what occurs at 24,25,26.

 

yeah, it sounds like fuel cut to me. It is supposed to happen when your MAF reading is too high for certain period of the time.

 

im positive. it hit 20psi and the car took off then bucked then took off again till i changed gears and then it did it again.



UPDATE
today it did it when i was by my self. in 3,4,and 5. no spiking or nothing. so i did some tests. i turned the mbc down 2 clicks. im still boosting at 20 psi but now it dont do what it was. the car pulls like a rocket till redline in all gears. can anyone help me understand this.

 

I think shiv knows the detail but I will tell you from what I heard and experience.
fuel cut happens when you suck in the dense air too much for certain period of the time. So, your MAF sensor reading will be very high. When your ECU sees this spike, it will cut off the fuel. It can also happen when your engine knocks like crazy or fuel pump fails...etc.