Postcard from Manassas

My wife and I were out washing and detailing our cars yesterday, and while we were doing this, my neighbors were doing some shadetree auto mechanic work that I figured you'd find entertaining. It certainly entertained me...

A few months ago, they bought an older BMW 3 series (maybe early 2000s-vintage) for their daughter to drive. It appears to have some sort of a fuel-injector or spark issue, or some sensor (crank position, throttle position, etc) that is out of whack. I still have no idea what the actual problem is, other than it appeared to be misfiring occasionally, at least at idle. I would have asked, but I couldn't think of a way to ask that wouldn't make me sound like a jerk. Either way, every so often it starts doing something "wrong" requiring him to apply his "expertise" to "fix" it.

What's funny is that it's pretty obvious that they don't have any idea what the problem is either, because since they've gotten the car, I've seen them do the following, repeatedly, with the most recent occurrence being yesterday. This was the first time I got to see the whole exercise, instead of just being annoyed at them for making noise that I can hear from inside the house. 

So, documented here for your reading pleasure...

Please complete the following procedure with at least 2 men, more are better:

1. start car
2. open hood
3. peer at engine looking for obvious problems (engine replaced by hamster wheel, major components on fire, significant fluid leak, large electrical sparks, etc)
4. let car idle for indeterminate period of time
5. while step 4 is in progress, repeat step 3 periodically
6. apply throttle to hold engine at 4000+ RPM for at least 5 minutes, periodically going to wide open throttle and bouncing the engine off of the rev limiter
7. if problem still exists, repeat steps 3-6
8. close hood, take car for test drive 
9. repeat steps 2-8
10. turn off car
11. go drink beer

As far as I can tell, this is the automotive equivalent of "if it jams, force it; if it breaks, it needed replacing anyway". In other words, abuse the engine until something breaks, and hope that this was the cause of the original problem. I guess it's a testament to BMW engineering that the thing was happy to sit in 100+ degree heat at 4K RPM without overheating or throwing a rod or something, though the miss did seem to get worse the longer they flogged it. 

 

The really strange thing is that these folks aren't slouches when it comes to fixing cars, during the downtime between steps 10 and 11 they did a brake pad swap on another car and recharged its A/C, so I can only conclude that this troubleshooting and diagnostic procedure makes some sort of sense to them...

 

Never a dull moment out Manassas way,