mustangmike9285

built a 331 stroker, has compucam 2040, bbk intake, 24# injectors,19lph pump, 70 mm throttle body heads with1.94" intake, 1.54"exhaust stainless swirl polished valves 180cc intake runners 58cc chambers, 1.6 rocker arms pedestal mount. fenderwell intake offroad h, flowmaster exhaust. have removed smog pump and blocked the head passages and removed ac, egr is not removed but is disabled, it runs good after 2k but it wont stay running when cold i have to feather the gas a while before it warms up a little bit and then it will idle at .5-1k and its ruff but i know it wont be smooth with the cam but i checked the plugs and one side looks ok and one side looks lean, it spits and almost backfires some times the engine has maybe 600 miles on it i get codes for lean on the one bank tps voltage at .97 i think just replaced IAC what would be the problem i think i might need a chip or something

mustangmike9285

im running 93 gas and still running 10w30 non synthetic from start up i got some royal purple im gonna put in at 1k

AdderMk2

have you done the base idle relearn proceedure?

mustangmike9285

im pretty sure i did it right where you disconnect the iac and adjust set screw then reconnect iac control. but that wouldnt explain the difference between banks

AdderMk2

I never said it did.

however, your car runs SEFI, which means that each injector is individually controlled. the ECM has the ability to lean out any single injector, or bank of injectors... try swapping your O2 sensors side to side and see if the plug results follow... you may need a new sensor

mustangmike9285

ill try but they are both new sensors and when i was running codes it switched them and and believe i still got the 91 code or one bank lean code, I was wondering if i need a computer chip or a new ecu, i dont understand what would cause all 4 plugs to be looking lean and the other bank look good

67mustang302

A bad O2 sensor will do that, it reads one whole bank.

And I wouldn't use Royal Purple.

mustangmike9285

yeah i replaced both of them and it still is doing it i checked the plugs again today i only pulled 3 or so but im still getting the same results the resistors on one side bank are golden brown and white on the other. whats wrong with royal purple i heard it was good.
it pops and gurgles alot is that normal. im using 93 octane but dont know if i should be running 87 or what any advice on that would be cool