Okay guys my car has been breaking up lately...& for some reason i cannot figure out what is causing it...the car idles, and drives perfect..but under boost at WOT around 13psi or more it startes to break up.

I have a 94 Sc300 with a 1JZ 5speed...
I have already changed the plugs, n gapped them to .028 i used Oem Denso Double Platinum plugs,i put in a Walbro 255,i did a 12volt Mod,i checked the coilpacks, & it all seems to be fine.

I kno its not boost cut because i have a Greddy Boost Cut & Speed Cut Controllers wired in aswell besides when u hit boost cut, u will get a CEL for about 2 secs or so, i checked for Codes and atm the car isnt throwing any, so im pretty SOL,

im wondering if the car just needs to be tuned, my car is completely stock jus BPU, stock injectors,stock turbos,etc

Please help!!

 

im having same exact problem

 

gotta love the dense winter air and how it f's everything up.

any fluctuations in afr's? going lean?

 

Dude, we already discussed this :P Get a wideband on the car, man! If you're leaning the thing out, its only a matter of time before you trash that motor...

 

Maybe try non platinum, NGK BKR7E (#6097)

Try .026 and if it doesnt work keep going down to the lower 20s

Also, you might pull your ecu fuse as well so that the ecu might relearn with the colder weather as a basis.

How's the fuel filter?

Was the car able to boost before or is this a new problem?

 

I never heard of a bpu 1J leaning out on 13+psi but we will see I have a innovate lc-1 wb, I was gonna put it in ova the weekend but couldn't cuz they called me in to work, so the wb is goin in 2day...

I bought a wideband bro, the next day...didn't get into installing it yet cuz of work, & the lack of time, but I am puttin it in 2day so the wb will keep me from guessing and will tell me if the a/f ratio is too rich or too lean underboost.
I've changed the fuel filter already before on the car when it was n/a, it hasn't even been 3 years yet, I also pulled the efi fuse to reset the ecu and still nothin

 

well guy's i didnt get the wideband put on today...my mechanic is busy with a build so i will have to wait i guess until he is done with the car he is putting a turbo kit on..SMH!!!

 

DIY man. LC-1 is an easy install. Just take it to a muffler shop to get the bung welded in.

 

When you switch to NGK 6097s, check the coil packs for cracks down the stems.

It's very common for them to get hairline cracks. You boost, the cracks open a hair and it arcs out and you break up. If they have cracks on the stems you can wrap them with electrical tape.

 

Yea the LC-1 is a easy install, but id rather wait cuz ima get a few more things done too...im committed to my shop, if i dont do the work my mechanic does... Grip Industries is the name of the shop

I double checked the coil packs today, and i saw 2 wit very lil thin cracks, like u said hairline thin, but also i decided to regap the plugs again, from .028 to .025 and the car no longer breaks up, lets just hope that it stays this way and doesnt start breakin up again, i will get the WB in asap and keep the boost at 15psi

 

Wrap those coil packs up if its the stems and you might prevent this type of issue later on.

 

Its not even 2 coil packs its 2 single coil stems, they arent even on the same pack..lol but i have heard about people wrapping them wit electrical tape.

 

Yeah electrical tape works just fine, just clean them off and wrap them up. My 1j was breaking up really bad and it was because of the coil packs.

 

so did u wrap ur coil packs or did u jus buy another set of coils packs??

 

That's what I meant, and wrap the stems.

New coil packs are about $475 for all 6, cost.