Misfires and rough idle with 8 news coils and plugs

[GEN 3 SHO FAN]

Hello 3rdgenlover,

Thanks for your experienced reply, your 2 cents worth probably some dollars. It's confirming what I found in TSB as I found not many troubles linked to O2 sensors here.

I'm completely approuving your comment. My goal isn't to cheat these O2 sensors, it's to understand where is precisely the cause of my misfire problem because I'm searching it since a long time and replacing these parts are costly and needs time to be replaced too. Running the car with sensors unplugged is for targeting which one(s) are bad (mistakes in replacing some of them will cost even more money...). I realize that cleaning intake involve removing all the parts now... In fact, the problem starts at this time and I thought that I have "misbolted" something on the intake after the welding.

This week-end we unpluged the 2 sensors on bank 1 (the hole on the Y is between them). The motor is even more cooler (needle at 1/4 - 1/5), some misfires stay but a lot less. Also I realized that the motor had a power loss because now it handles overdrive at a lot lower rpm... (1500 rpm rather than 1800 rpm).

As the PCM cannot "see" this hole on the Y and misfires stay, I think now that all 4 sensors were probably contaminated by my cleaning (I must admit that I did it in a way that it don't have to be redone soon...).

Maybe I can replace them by used ones as almost nobody had troubles with these parts ? (I will make a check up on TCCA before doing this.)

Thanks for yours advises,

 

[Qshiplvr]

Update on my O2 sensor replacement: Both upstream and downstream sensors now replaced. My Mitsu drives like a newer car!

 

[gamefanatic]

With all these eletronics, and with so many that can exhibit the same symptoms, its good to hear you were able to track this down!

 

[GEN 3 SHO FAN]

Thanks all. I hope it's the problem but I haven't repaired yet. I found a set of 4 used on e-bay (as all my sensors seem not good). I will replace them next year probably as winter is coming here. (I will keep you on touch then.)

Update : If some misfires stay after I unpluged 3 sensors. It is right to affirm that the PCM can also adjust his A/F ratio with downstream sensors ? The only one that stills pluged is the downstream of bank 2. Or my prob is elsewhere...