Thread: Bucking issue at full throttle

Hi, maybe someone can help me out with a problem I am having.

My car has started "bucking" at full boost. If i go partial throttle and keep it in the 5-6psi range the thing pulls hard to redline. If I go full throttle (8psi) the car bucks as if it is cutting out as I am accelerating.

I recently moved from Hawaii to Virginia, the car has been sitting for almost two months while in transit and then over the holidays while I waited to get it registered. It definitely did not do this before I moved. Engine has about 30k on it since rebuild and has run with no problems. The battery did die in transit and has been working OK since I jumped it but it seems to only last a day or two before I need to jump it again. I am also still running a stock MAF and I know I am near the limit of that MAF. With the air being probably 40 degrees cooler is it possible I am getting too much oxygen for the MAF?

Any help would be appreciated, here is my setup:

stock B13 MAF
Toda cams and valve springs 264 duration w/ 10.5 mm lift
Ferrea stainless steel valves
crower titanium valve spring retainers
new nissan cam follwers
9.5:1 pistons
cometic metal head gasket with arp head studs
unorthodox racing crank and water pump pulleys
outlaw engineering thermal spacers
hotshot cold air intake
gt28rs turbo (brand new with approx. 1,000 miles on it now)
jgy turbo kit w/370cc injectors
jgy 2.5" mandrel bent exhaust with magnaflow mufler and resonator
msd 6A-L ignition with ss blaster coil
jwt computer (programmed for stock MAF, stock fp, 370cc injectors)

Do you smell fuel when the motor is bucking? Mine is still doing this as well and I'm thinking it's my tune. Car is running very rich and I smell tons of fuel when I go full throttle.

On another note, welcome to VA. Sorry to hear that you left a much better place such as Hawaii, but there are still some SR20 guys holding it down around the 757 area. I'm located in Norfolk if you ever need a hand. Let me know if you resolve your issue.

Build a leak tester and test the system it sounds like there is unmetered air getting into the motor.

I dont smell any fuel, it runs perfect except when I go full throttle. Its a really strange problem.

Thanks for the welcome... Im actually from Chesapeake and I prefer living here but I could see why you might say that. Especially in January. Have you been to Hawaii? Dont believe the hype, it is OK but it is NOT paradise unless you make a million dollars a year. Trust me.

My first thoughts would be an ignition issue. I'd look for fowled plugs or deteriorated ignition components first. Something is causing a weak spark I think.

I will go check the plugs, it is cold as a bitch out today though so I may wait until the sun gets a little higher.

In a related note, the car is also idling high (maybe 1500rpm) and has even been loping a little bit. It used to idle smooth at 1000 before the issue started.

I found the thread about building those. I will check that out.

Plugs are all white, so I think you may be on to something.

Also noticed that I dont hear the blow off valve much at all. Used to be loud enough that I definitely could hear it when I shifted gears, now there seems to be nothing.

sounds to me like you have a boost or vacume leak

Just a quick question though, how would unmetered air get in under boost? Wouldnt you see the opposite affect since the system is pressurized? Wouldnt air be escaping out of the system (boost leak) and the car running rich because the MAF is reading more air than is actually reaching the intake manifold? I am a little confused.

Depends where your MAF is. If it's draw-through then you could have unmetered air while in boost. If it's blow-through then you're right, it's not really possible.