okay so i got my mpfi done. everything was wired properly. it was throwing a code 9 and then i replaced the distributor and then that code went away. now the car is still running like crap. it stalls and sputters and backfires in the intake manifold. i took it to a local performance shop and while i was driving it the cel kicked on and it was code 1 which is the o2 sensor. could a o2 sensor make it run really rich? i mean i could smell it running rich and i can feel the heat come through the floors from the cat/exhaust getting so hot. im not sure about timing.

-can a bad o2 make a car run really rich and make it backfire through the intake?
-were should my timing be?
-the guys over at the shop said it might be a stuck open injector that is causing this but it doesnt make sense?


its a stock d15b2 with the mpfi swap off a 90 civic si (pm6 ecu)

 

Sounds like O2 sensor to me. Mine came a little unscrewed...motor ran like crap.

Don't go by my sole opinion though, i'm pretty miserable at diagnosing problems.

 

bump, thanks for the input

 

It might be your timing as well. I was running 4 degrees advanced and didn't know it and kept throwing code 1. I changed it back to 0 and the code is gone now.

 

mine started doing the exact same stuff as yours after i did mpfi because i put it in 2nd on the free way going 60 :/ but all i did was change my o2 sensor and it runs fine now..

 

By your description, I will bet the O2 sensor is only the "messenger", not the problem. You've got some timing issues or valve problems (backfire through intake). Depending on your wiring expertise and all that is involved, an open injector could be the cause. (BTW, the ECU grounds each injector to trigger them for whatever duration is required at the appropriate time.)