Changed Co2 sensor NOW have CEL!!!

[teamslacker]

Hello forum,
Noob here.
1990 325i just purchased and need to get smog in California. Had NO CEL, so I figure I would change the oil, the fuel filter and the CO2 sensor to get it ready to take to the smog station to make sure it would pass. After doing these things, now the car runs like crap and the CEL in on, and the CHECK light on the dash is flashing. Oil level is fine, fuel filter is orientated correct, and the Co2 was just a swap. I have disconnected the battery a few time for up to 30 minutes with no change. Any help would be greatly appreciated. Though I have worked on many cars this is my first E30 so I am a bit clueless. Thanks.

[FLG]

Was this a new o2 sensor? Did you try putting the old one back in?

[teamslacker]

just switched out the o2 sensor with the old one...same issue. I have no idea what is going on here.

[FLG]

You said you changed fuel filter, thats in the engine bay on that car no? so had to remove air box and stuff (sorry i have early model)

Did you make sure you remembered to plug back in your AFM and idle control valve?

[nickmcc92]

Pull up the code. Do the stomp test and see what code you come up with.

[teamslacker]

Thanks for the help so fat FLG, the fuel filter on the E30 is under the care next to the tank, but guess what you just fixed my problem...I changed the air filter a few days ago and haven't started the car since....and I forgot to plug in the connector on the filter box....LOL, a half day of frustration due to a plug that was right in my face.....thanks for the help.

[FLG]

No problem, have done it myself. Ive learned that when doing separate jobs its sometimes good to start the car up when one is complete just to minimize where a problem could exist.