My recently acquired 89 DL auto starts violently - when the first cylinder fires, the engine stops (stalls the starter), then continues to crank, which will either start the engine or maybe fire violently again and stall the starter. The battery is hot, the starter seems powerful.

It seems like preignition, but it does it hot or cold.

Once running, it idles fast, just misses a little and has decent power - runs a little rough though. I changed ECU to a 951 and made no difference.

I threw the timing light on for fun (I know the ECU controls timing) and spark is way advanced at idle. I have an identical 89 DL and the timing is about TDC at slow idle. ANY ideas?

Be careful assessing ignition timing using the mark on the damper -- it is frequently slipped and not really TDC. You can pull plug #1 and feel TDC with your thumb to check the mark, then use some white-out to paint a line across the rubber vibration damper to gauge any later slippage if it is OK.

Any evidence of recent timing belt replacement? The distributor could be off far enough to deliver the crank-timed spark to another cylinder, or just carbon-tracked enough to do so even if it is lined up. See the 700/900 FAQ for block mounted distributor marking.

I've had a similar experience with a track in the cap that eventually wrecked the starter.

Not in my experience, but I believe suspected by someone else on the board: faulty crank position sensor - perhaps weak enough the ignition controller misses count or counts extra from its index on the flywheel ring.

Yes the crank position sensor can cause this. I had one with frayed wires, and it would regularly stop the starter dead in its tracks. The car would also not start at times, until I gave the CPS wire a jiggle.

I have also had this happen with the 25 amp fuse under the hood. Intermittant loss of power through it caused all kinds of weird symptoms including backfiring the starter to a stop. This stopped after I replaced the fuse holder.

The first thing that comes to my mind, which is admittedly slow and suspect, is a bad TPS or wiring. The ECU 'thinks' the engine is not at idle, and throttle is open.
--
Gary Gilliam Sumerduck VA, '94 940 na Regina 150k, '86 240 180k

How do I check the TPS? Is it the device that clicks just off idle at the throttle? If not, what is the correct way to check?

How do I check the CPS? I have a scope, meter, etc.

Thanks for all help!

What is the TPS as I'm am having the same problems.

TPS= Throttle Position Sensor.