car has d16z6, tuned with two step and the other day my alternator was going out because my interior lights were acting weird and when it started going out the car would just start going crazy after about 50% throttle no matter what rpm or gear. i figured it had something to do with the alternator being bad and when i replaced it the problem still persists. it will just sputter and bounce around at about 1-2k rpms when you push the pedal all the way down. if you keep the throttle below half, it will go smoothly through the whole rev range and still initiate vtec. the funny thing about it though, is that when my car is cold, so it gets a CEL and it runs very weird and the idle jumps between 1800-2000 like it has a cam in ur and it won't go past 4500 rpms and when it is in that state, the sputtering problem does not exist and i can't get the car to sputter at all. after driving the car for a while and getting it warm, the CEL will come off and it will run fine and idle perfectly fine other than the sputtering past 50% throttle. the CEL light being on and the car running bad when the car is cold has always been a problem but the sputtering is new. it could just be the ecu because there are other problems that pertain to the ecu (like how it runs completely different when it's cold) but i'm really hoping it's something else because i don't want to spend 300$ on a new ecu if anyone has experienced this or has any ideas please lmk (i also have replaced plugs and wires)

edit: my speedometer also stopped working when my alternator did and it never started working again when i replaced the alternator, i even replaced the speed sensor and nothing, speedometer is stuck at 0

 

What codes are being thrown when your check engine light comes on?

What type of plugs are you using and what are they gapped at? You should be using NGK brand plugs, part number ZFR5F-11 (these are pre-gapped to 0.044") if your engine is stock-ish.

You say it was tuned - I would take it back to the tuner and have them look at it. What hardware do you have which allows it to be tuned?

Have you checked all your fuses (under-hood and under-dash)? Is there any shoddy looking wiring on the car? Interior lights still act weird after the new alternator? Describe how they are acting.

 

i have tried to read the codes, it doesn't give me any, the light is just on.

i just bought brand new double iridium plugs gapped at .044.

it has an ssr chip in it with a tune on it

i will re check all of my fuses, my lights act mostly normal now with the new alternator except that when the car first starts, the lights are just SLIGHTLY just a little tiny bit dim and the air is just a little tiny bit less powerful, but it's not noticeable and when i rev it up to about 2500 the lights and the air turn normal and it stays that way until i turn the car off

 

Not giving you codes (this is "code zero") typically means a bad ECU or a bad install if it is chipped/socketed. If the chip was not set up for your specific car, that is most likely the issue. You can try reverting the ECU back to stock by opening the ECU and cutting jumper J1. If the car runs fine, the issue is with either the tune on the chip not matching your setup, or the installation of the socket and other components in the ECU may have been poorly done.

What is the part number of the plugs you bought? Make sure there is an "R" in the part number (this indicates they are resistor type plugs).

Lights being dimmer upon startup is normal.

 

what if i cut the jumper and my car is f*cked?? do i just have to buy a new ecu? i'm afraid it won't work if i do that

 

If your car does not run after cutting (or de-soldering) J1, you can simply reinstall a jumper. The only thing that happens when you remove J1 is the ECU no longer looks at the aftermarket ROM chip that is installed and instead looks at the OEM programming.