Another CEL question

Hello, I have a recurrent CEL in my 1997 328i and am wondering if anyone has had a similar problem. I recently replaced both precat o2 sensors and all 6 ignition coils. Coils were done as some housings were cracking and arc points could be seen, o2 sensors were done for CEL code for out of range on bank 1-3. Car has 198k on it so I replaced both sensors. I used all proper bosch parts (no splicing sensor wires) and reset the light with my code reader that plugs into the engine harness under the hood. I did not use the OBDII port under the dash.

For about a week, the light stayed off, car is running smoothly and everything is grand, then the CEL comes back on. I scan again and am getting codes on both precat sensors for "adaptation limit" and "control limit" ... I cleared codes again and again, in about a week and 200 miles or so, the CEL is back on and the same codes are present. Has anyone else had this problem?

I read through your thread and replies, it does seem we are hunting similar gremlins. My cyl head and exhaust / exhaust manifold have never been off the car. My CEL is particularly maddening as it doesn't come right back on, it waits just long enough to make me think I've cured it and then HA! annoyingly bright yellow light is back!

In the 3-4 times since o2 replacement that it does come back on, it has always been while idling (at a stop light for example) never on the freeway or while under power.

Check for any unmetered air leaks is there is one it can cause a adaptation fault to set.

At the risk of bringing it back by mentioning this, my CEL has stayed out for the past 10 days. Let's see if this can continue.

I shouldn't have mentioned it ... it's back on. This time codes are again "adaptation limit" and "control limit" but confined to cyls 1-3. I have been looking for vacuum leaks but so far nothing. Anyone have "next" ideas?

Can you get the global obd2 code number so we know which way the adaptations are going rich or lean.

Sorry I haven't replied for a few days, I need to get my OBD code reader back from a friend. I've noticed a new engine behavior as of late, when idling after driving, the idle will be initially smooth, then the engine will run rough to the point where I can feel it shake the car nearly like an ignition miss. If I let the car continue to idle, it will eventually go back smooth. There is no stumble at speeds. I am thinking of pulling the IAC valve and cleaning it, but it was fine when I replaced the oil breather trap about a year ago. Is there another emissions valve or similiar that would cause both the idle miss and the CEL? The codes are still the same for o2 sensor 1-3 adaptation and control limits. I will try to get the OBD codes soon. I thank all of you for your help!

Ok, so after the last post above and driving the car for 1500 miles or so, the CEL has not come back on. There are no additional codes stored and the car is running fine. Whatever was triggering that code somehow corrected itself. Go figure!