having an issue with a b20vtec.

95mm crank
12.1 pistons
obx itb setup
id 750s(from turbo setup)
255 fp
s300

car ran great on the stock b20vtec, tried using the old tune but no help


using tps (alpha) for both maps, seems to get the car to idle, triped map on primary and tps secondary car wont even attempt to idle... so tps on both maps it idles at 1500 but however its misfiring on cly 1,3

swapped the dizzy, wires, compression test said 230 compression across the board

ive tried everything i know... and cannot figure out this misfire, s300 has no check engine lights, tps reads 0 off gas 100 % full throttle.

need help.. im stumped..

 

Whats the afr at idle?

 

15.7-15.9 maybe a little less..

 

Thats way too lean, possibly because of the misfire though. Try richening it to around 14.5-14.7

 

timing?

 

how do your obx itbs idle? also what fuel are you using?

 

Have you had the car tunes since itbs?

What I'm gathering is it was tuned, then the itbs were installed, then you are tweaking the tune?

 

if its misfiring on 2 cylinders only, then it doesnt sound like a lean/tune issue to me. did you do a valve adjustment? , check the injectors/injector wiring? also check the spark plug/gap - firing order

 

Hi,

Are your ITB's balanced. There is a air screw on the OBX where the runners start just above the throttle plate which need to be set. You probably need a mercury balancer or similar.

I had similar issues during setup but lucky for me my tuner was very experienced with ITB's.

Attaching pic of the balancer for reference.

Jignesh