Help: Check engine light and poor idle

[dtdub]

I need some help to trouble shoot an issue that just came up.

I have a '91 318is (M42). When I tried to start it up this morning it stumbled a bit, then the check engine light came on, and then the engine died.

I tried starting it a few more times and it would rev up to ~1600rpm then slowly come down, and finally just stumble and die. I tried a few more times with similar results. The check engine light remained on throught.

I'm not sure if this is related, but for the last 2 months the car has been cranking really slow. Once it starts it runs fine. I thought the battery was toast (still has the orginal), but replacing it with a good optima yeilded the same results - so I don't think it's the battery.

How do I hook up and read the code? Any ideas?

[txleadfoot]

my bet is a vacuum leak. check the intake boot and the funky hoses underneath it. as far as the codes, turn the ignition to run (w/o starting), and stomp the accelerator five times in succession. i don't have my list handy, but i'm sure someone here can point you to a write-up to read the CEL blinks.

[dtdub]

I borrowed a code reader from a friend, and the only fault that came up was "vehicle speed signal missing". I expected this since I've been having speedo issues ever since I replaced the diff.

After clearing the code, it started right up like normal! So now I'm really confused. The idle isn't that great normally, so maybe my idle valve is going out. Maybe it was stuck for a while, causing it to die right away.

I couldn't find any vacuum leaks anywhere.