Hi Peter:

Thanks for the reply! Your diagnosis seems pluasible as the car does seem to be problematic when hot. I have two other points to mention:

If I stop the engine hot, wait 1 minute, and restart, it starts right away, but then the rpm drops to like 400-500 and then after a few seconds it recovers back to 750 normal rpm. Almost seems like a loss of pressure as you say.

If I stop the engine longer, when I go to restart the engine fires right away but dies right away also. Then you have to crank crank crank and after 5+ seconds of cranking the engine goes brup brup brup (if you apply no gas at all during starting), catches at something like 200 rpms, and shakes and hesitates for several seconds as the rpm SLOWLY rises to normal rpms. If I rev the engine for a few seconds this speeds up the process of getting to a stable idle at 750 or so.

I did remove the cold start valve and try to start the engine with it outside, but I never observed any gas coming out of it while trying to start. I was not sure it was working right. Then I bought a new cold start valve sensor and replaced it, as well as replaced the cold start valve with another from the junk yard. It does say on the sensor -5C 20 second delay, so then I thought maybe it only works if the temperature is below freezing and not for every day. So due to this, I don't really know if the cold start valve is working or not.

This morning when I started the car cold, about 1 second of cranking and it starts, hesitates for 2 seconds and is at a stable idle at 750. This is all with no gas pressed. Seems better than hot start, but not perfect nevertheless.

When the car used to be perfect, I used to crank for 1 to 2 seconds and it would catch and run smoothly right away. When the engine warmed, it would slow down the idle rpms a bit. Not that I say that I don't ever remember seeing it now slow down after warming the engine up, so something is wrong there from the start.

I don't have any specialized equipment and I don't believe I have an aftermarket computer. Looks like they just spliced the wire from the O2 sensor into one of the computer wires near the connector. I didn't untape it to see, but that is what I see by following the wire from the O2 sensor.

Where should I look for the conector? I looked at the throttle body and I have a connector in the back side. Is that the one? I would like get the system to run in "open loop" and see if the starting problem improves or gets worse.

Please let me know what I can do as the average mechanic without any special tools. Your advice is greatly appreciated!

On the lighter side of things, I flushed my radiator out this weekend (havent done it in several years!) and I installed a new thermostat in the housing. Now my car drives at a solid 87C down the road at normal operating temperature while it used to be around 80 or less in the past. One thing fixed!

-=>Raja.

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1983 MB 190E, bought from Germany and shipped to the US in 1986.