Hello, all.

My wife's '91 240 has developped a "Check Engine" problem. I pulled the codes off socket 2 in the diagnostic box and came up with 221 and 231. Socket 6 had no trouble codes. I cleared the codes, but they keep coming back right away after I start and/or drive the car around the block.

According to the Bentley manual

221 means: "Fuel system compensating for extremely rich or extremely lean air/fuel mixture at cruise"

231 means: "Fuel system compensating for rich or lean air/fuel mixture at cruise"

At least the two messages are consistent. The 221 will light the CE light, the 231 won't.

So, what gives? Where do I start? Is this a common thing? Should I check the O2 sensor? There is a code for that, but it is not coming up. Should I look into fuel pressure? Please help, someone, the car is overdue for an inspection sticker and I KNOW it won't pass with the CE light on. Also, I think the car started to ping a bit, which I have not noticed before. Also sometimes it idles rough, but not all the time, in fact it happens infrequently.

TIA, as usual.


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Vladimir. '98 S70 base, 5-speed manual (his), '91 240 sedan automatic (hers).