Sabinsharon

Hey guys I recently put 39 pound injectors in and pacesetter LT headers the car ran with injectors only. After putting in the long tubes it ran rough. Changed oxygen sensors wouldnt even start. Swapped old o2s back in still wont start at all. Check engine light blinks but has no codes.... This is all trying to run it with open header. Gin to bolt on a makeshift exhaust tomorrow see if having the o2s so close to outside is causing it on the upstream side other than that anyone got any ideas on what could be the problem.

moosestang

Do you have a tune for the 39lb injectors or headers?

AMWill

OP,

You're going to need the PCM calibrated for the larger injectors, like moosestang mentioned. Otherwise the fuel trims will be completely out of whack. That's probably why you aren't able to get the car to start.

Any customer tuner will with a reputable tune should get the job done!

Shane

moosestang

yeah, if it's not tuned for the larger injectors, then it would be subtracting fuel like a mother or would it be adding? It'll be messed up, that's for sure.

Try holding the accelerator down while cranking to clean the plugs, then try to start it without holding it down. This would only be a temporary fix, but will tell you if the plugs are fouled.

I wonder what your start up air fuel ratio looks like. I bet it's either really, really lean or really, really rich.

Sabinsharon

Its rich. It ran for a while the computer adapted to just the injectors but I reset the ecm while putting headers on and now I think the computer is confused as ****. It ran for a while with it but it doesn't want to do **** now lol tune date is march 15 with hpp gonna go ahead and put cams in while I wait

Sabinsharon

Update. Replaced plugs they were 110000 mile original plugs swapped them out changed injectors back to stock welded new exhaust and purrs like a kitten now

AMWill

The entire injector scaling will be off and running rich. Then the O2's will pick up the rich mixture and try cutting the fuel down a little at a time, but it won't be enough for the engine to run correctly. Even if it were to adjust itself for normal driving (after a LOT of cycles), the WOT fuel mapping will be so rich he'll probably foul the plugs after a few runs.

Shane



Good to hear you got everything straightened out for now! Definitely wait for a temporary tune before installing the larger injectors again. Or just take the car to a dyno shop and install the injectors on the spot.

Shane

Sabinsharon

Yep it goes to the dyno shop on march 15th. Im reinstalling injectors doing stage 3 vsr comp blow cams valve springs and phaser. Ill let them do a tune before they start it then they can tweak it but it wont be driven till then.

808muscle

Without going FI why the need to change the injectors? Glad you got it running again.