What went wrong?
 

Here's my series of events (I searched):
1) Trans Fail Message a few days back, but nothing unusual happening. It threw this when I turned the X off after a brief drive. I got nervous about it, restarted it and drove around the block to see if the code came up again. Nothing displayed this time.
2) Yesterday, I cautiously drove it to a destination 25 miles away, nothing unusual. No codes. Completely uneventful.
3) On the way home (after approximately 15 minutes of driving), the CEL illuminates and, when accelerating or keeping the speed up on the highway, the X vibrates and the accelerator feels like someone shoved a sock in the exhaust (only way I can describe it). Now, when it is idling, it's very choppy, even from a cold start.

I am going to take it to the dealer for diagnosis, but would like to gather some informed opinions in case it's something minor I can do myself.

It's a 2003 3.0i with 68k and is not driven daily.

Any clues?

Could be something as simple as a bad sensor, or it could be a sign of more major issues. You may be able to diagnose and fix it yourself if you have an OBD-II code reader. If not then you are going to have to rely on the dealer to do the troubleshooting for you.

:goodluck:

Unfortunately, I do not have the required code reader. I'm hesitant to drive it to Autozone where they (reportedly) will do a free scan and give you the codes.

I hope you're right with it being a sensor!

See what code it's throwing. The rough idle and CEL are probably related to a bad plug, coil pack or an O2 sensor? Could be a number of things.

Not sure about the trans fail safe.... it's a mystery for many.

Unplug the MAF sensor and see if it runs better.

Bummer - I unplugged the MAF and it didn't change the behavior. It also threw the dreaded "TRANS FAIL SAFE" - she's headed to the dealer tomorrow. I'm hoping for the best on this one.

Might be a good idea to tel them you tried unplugging the MAF on a hunch as so they don't get misled by the fault code caused by unplugging it.

I will absolutely do that - thanks everyone - will update this thread when the root cause is discovered!

Update - just talked to the dealer who said "the computer isn't pointing us to the problem - it's vague and just saying it is misfiring". They asked for another hour and a half for manual diagnosis and I ok'ed that. I'm frustrated with the fact the computer didn't pinpoint the problem and now they need to "experiment" at my cost.

Final update, the X is fixed and running like new again.

The cure was a new set of spark plugs ($345), but I also had a BMW inspection ($445), a coolant flush ($80), an hour and a half extra time for them to diagnose the issue ($150), and a brake flush ($100). Total pain: $1215

In the inspection they found some other issues. I'm wondering how many of these I can cure myself?
> High Pressure Power Steering line - they say it's leaking but the car is stored in a clean garage. Never a leak on the floor for me...
> Fuel intake flush/clean
> Front and outer CV boots - they say the CVs are "about to crack". How can you tell they are about to crack?
> Battery - I'm sure I can handle that one.
> Tail light assemblies are corroded.

Thank everyone for the pointers.