CEL won't go away!! Please advise...

[brickbek]

Hi everyone!

Good to be here.

This is my first post on Matthew's about my first 1989 240DL, 152k miles.

She has been running smoothly since Oct. 2008 when I bought her.

Here's the deal now....as of a month ago.

CEL light went on. Code 2-1-2. Mechanic changed the O2 sensor under the car. Then CEL 1-1-3, 2-2-1 came on with a rough idle and major drop in gas usage. I used to get 220 miles on 12 gallons, now I get 130 miles...ouch.

I began to read everything I could about this and between my mechanic and I we changed the FPR, I cleaned the Throttle Body, New Fuel Filter, New Air Filter, Checked the AMM and hoses for leaks, including the accordion hose...all okay. Fuel injectors are all good! He changed and tested the O2 wires (relay) under the hood and had it smogged with good O2 results... good voltage.

I then went to a salvage yard and swapped my pink label #561 ECU with a yellow label #556. Things changed a little. The 1-1-3 went away and gas mileage became a little better, just a little maybe getting 170 miles per 12 gallons.

The only things now with my #556 ECU, are still drinking more gas than it should and a bit of a rough idle AFTER the CEL light comes on. When I clear the code, it purrs and runs smoothly, then after the code is cleared (disconnecting battery and pulling the 25A fuse) 10-40 minutes later, the CEL is back throwing a 2-2-1 code. Idles a bit rough again.

Runs very well other than a rough idle after the CEL light comes on and more fuel consumption than it used to have.
I've poured two treatments of Chevron Techron in the tank as well.

What does a girl do next? I am determined to get that light off.

Please advise oh wise ones...thank you in advance!

Rebecca

[vegasjetskier]

[quote="brickbek"]Mechanic changed the O2 sensor under the car. Then CEL 1-1-3, 2-2-1 came on with a rough idle and major drop in gas usage. I used to get 220 miles on 12 gallons, now I get 130 miles...ouch.
[quote]

This makes me very suspicious. Did you install a Volvo brand 02 sensor?