Car bucks and spits under full boost over half throttle

[Bradman123]

i dont have any boost leaks, i pressurized the whole system from turbo inlet to the throttle body and it holds 15psi easy with no air seeping. today was kind of cold outside and it seemed to do it worse then on other days, and the boost came up faster. if i watch my boost gauge it actually spikes to 10 comes back down to 7 and when it bucks and spits and bobbles around between the two. i have no boost controller and i have a line running from my throttle body where the vacuum canister would go running to my wastegate instead since i tossed the canister. i have one line going from my tb to my bov to the big nipple. the small nipple on the bov is not being used. i have the stock t25. is it possible that my wastegate is messed up? how do i test it? could my intake manifold gaskets be leaking under boost? or the tb gasket? would an exhaust leak cause it? TPS going bad? or the mafs going bad? how do i test the tps? thanks for any help!

-Brad

[s13dan]

sounds like a fuel cut... do you have an after market fuel pump or a stocky? and what injector set u7p do you have? with stock fuel pump you cant push more than 10psi... i have tired

[Bradman123]

i have a walbro 255 that i got off ebay. i checked all the numbers and the pump looked like any other walbro i've seen and had the emblem stamped on it. so unless its deffective thats not the problem. i have the stock fuel injectors. and my car should be only running 7 with the stock t25 wastegate. but it appears to spike to 10 when it bucks. what would cause fuel cut?

[statik]

Redo your vacuum lines, hook up the intake piping nipple (before the TB) to the wastegate. On the upper TB the larger line goes to the BOV, and the smaller one goes to the FPR/Boost Gauge. The bottom line on the TB just plug up. Try that see if it fixes anything...

[Pepperoni]

Check timing

[Bradman123]

k, i made my own piping, and i had a bung on the hot pipe i made but my hot pipe was leaking like a mofo through the bov flange so i just bought a hot pipe from enjuku. since i didnt have the bung like i did before i decided to use the vacuum nipple on the tb for the canister since i didnt have the canister anymore. i spose i can put a nipple on one of my other pipes, and vacuum cap the canister nipple. and about checking timing. i dont know how to use a timing light. or i would have done that 2 months ago. so this very well could be the prob. someone wanna tell me how to use one quick?

[nrcooled]

I had the exact same issue that you have now. Easy fix though...gap you plugs. You gap is too big now and needs to be smaller (.027-.030) When it is cold out the combustion is larger and you are blowing out your plugs.

Everytime it got cold I would have the same problem and finally I figured it out after doing everything that everyone else is suggesting to you. Even if you have already gapped the plugs check them again.

[Bradman123]

i got my plugs from heavythrottle in their install package that they sell, came with fuel filter, plugs oil filter belts etc... i asked them if they needed to be gapped. and they said no. they should be fine out of the box. i'd imagine that they are sr20det plugs...and the car doesnt do it just when it is cold. it was worse yesterday when it was cold but does the same thing when it is warmer out. i am going to get a timing light tomorrow and attempt to check it. i could use some better instruction on how its done though. if the timing is right, then i might try to wire in my mafs from my sohc and see if that fixes it. or i could clean my sr one. what should i use to clean it? how can i test my tps to see if that is the problem?

[nrcooled]

Even if you have already gapped the plugs check them again.

Read above quote. Jeff and Yuri are humans and can make mistakes or forget stuff (they are great guys and I gave them tons of business)

[Bradman123]

i took my business to enjuku and phase 2 after jeff and doug both got extremely rude with me when i was trying to figure out why a shit ton of oil was coming out of the front of my motor. found out it was a gash in the front cover right in the pressure port of the oil pump. they didnt have the patients to help me and turns out they sold me a damaged motor so i said screw em. so ur pry right. ill check the plugs before i check the timing. thanks. more ideas will help though in case this isnt the problem.

[Bradman123]

if the plugs end up lookin extremely fouled up cuz the timing is off or they arent gapped right, what plugs should i replace them with that i can get locally.

[kungfucowboy]

don't know it will help but when my horse used to buck and spit i would stop him get off punch him in his long nose and that tended to stop the bucking and spitting for atleast a day.

[Bradman123]

oh he he im sure ur horse loves you...but ur horse doesnt have an intercooler on its nose.

[nrcooled]

Boch plugs or Autolite. Doesn't really matter. I would go to your pepboys/autozone get plugs for a b13 SE-R sentra but make sure to get them two heat ranges colder. Gap to .027~/.030 put them back in and go for a spin.

[Bradman123]

right on guys, i got my timing light and checked it, i believe it was retarded about 5 degrees or more. so i set it to 15bdc (2nd from right notch) took the car for a spin and the problem was virtually gone. it bucked twice on average each pull and i went about 3 times. i brought it back home. checked timing again and tweaked it just a tiny bit to get it exact. when i set the timing the first time i just put the timing light clamp deal on the wires going to the coil and it seemed to work the 2nd time i managed to get it to pick up the signal from the loop in the back. either way they were the same. i disconnected the tps when i set the timing. then i plugged the tps back in and tried to check the timing again it seemed like it was jumping all over the place at idle...is this normal it went from about 10bdc to 20bdc and stopped in the middle at 15 a couple times. to me this doesnt seem right. why is it doing this with the tps plugged in? i still need to check my plug gaps, im letting the motor cool down and i disconnected the battery to reset the ecu. so im just chillin for about a half hour then ill go check the plugs and take it for another spin. wish me luck!

[Red]

With the stock ignition system I had to gap my shit WAY small to keep the spark from blowing out...

I had the EXACT issue you have.

[Bradman123]

car is fixed, after putting better clamps on my fuel lines out back and tightening them as tight as i could, and then adjusting the timing to bo correct. i drove it and it still bucked a couple times. so then i let it cool down and gave the ecu time to reset with the battery unplugged. i put the timing light on it again and fine tuned it a little more so that it would be EXACTLY on the mark, then i gapped my plugs between .027-.030 instead of .045 that they were. now the car pulls unbelievably smooth all the way to red line. and for 7 pounds of boost im suprised at how fast it actaully is...thanks everyone for your help. and i hope my experience will help others in the future.