help! engine shuts off 20 seconds afer start if idling

[benzdude]

I have a 95' c280. When I start the car (in park) and just let it idle,
The engine shuts off. I can reproduce this everytime.

seems to work fine if I start it and drive off. ( before the 20 seconds.)

anyone have a clue?

benzdude.

[Denlasoul]

sounds like your rpm's are droppping below 500. typically, the MAS sensor is the culprit, but I'd look over your O2 sensors, wire harness, plugs and such.

[98_Benzo]

I am going to go with Denlasoul on this one. Sounds like the MAF or the O2 sensor. Do you have aftermarket exhaust on your car? Do you have a K&N air filter? Once you get us this info, I can go more into it.

[JDoggery]

Originally posted by 98_Benzo
I am going to go with Denlasoul on this one. Sounds like the MAF or the O2 sensor. Do you have aftermarket exhaust on your car? Do you have a K&N air filter? Once you get us this info, I can go more into it.

Can you explain how an aftermarket exhaust or air filter can contribute....

thanks

[Denlasoul]

Originally posted by JDoggery
Can you explain how an aftermarket exhaust or air filter can contribute....

thanks

not too sure about the exhaust, but for an aftermarket filter (one that may use oil to assist in collecting dirt) there can be residual deposits from the actual filter that tends to collect on the MAS wire.

[98_Benzo]

Can you explain how an aftermarket exhaust or air filter can contribute....

Well I did mention the O2 sensor maybe being bad......where is the O2 sensor located?? On your exhaust, sometimes when the exhaust system is not done right, you can burn out your O2 sensor, I've had it happen.

[Denlasoul]

Originally posted by 98_Benzo
Well I did mention the O2 sensor maybe being bad......where is the O2 sensor located?? On your exhaust, sometimes when the exhaust system is not done right, you can burn out your O2 sensor, I've had it happen.

err...yeah. that's what i meant to say. :)

[Rocky]

sounds more like an OVP relay to me. those are comon problems for your year of w202.

A MAS or wiring harness or O2 should generate a CEL light.

[moebiusgold]

Check this out:
OVP problem (http://www.mercedesshop.com/diy_stevebfl_1.htm)

[benzdude]

thanks guys for all the info.

I dont have aftermarket exhaust or a K&N air filter and I had the rear o2 sensor changed a couple months ago. (hopefully it was the correct one). The engine harness has also been replaced already.

I hope its not the MAS.

wednesday I am taking the car into the dealer to get an oil change and I have instructed them to look over the problem.

I will also buy a new over-voltage protection (OVP) relay (i love my car). I think is about $75+.

The tricky part is that the cel has been on for a while, they pulled/reset the codes (at the last oil change) and told me what the problem was: P1700 upshift delay switchover value control. (the cel came back on later that day). it semed like a minor issue at the time, hopefully I havent caused bigger problems.

wednesday, I will have them pull the codes again and check the rear o2 sensor installation. (it was done by a non mb person)

today, I will change the spark plugs, check the wiring and do a little looking around.

anyone know where the fuel filter is located? I want to rule that out.

thanks,
benzdude.

[moebiusgold]

Fuel filter is back by the trunk on the right side.. Above a removable plastic cover.