I don't know the test procedure, but have seen it described in some of the posts. It has to do with checking voltage across the terminals. I've got a nice volt-meter my son uses when he comes to visit. ha!

It's a nice sunny day here in NW Florida today, so I'm going to pull my idle speed control valve off and try to clean it with some carbuerator cleaner this morning to see if that cures the problem. I hope there's nothing I can mess up by doing so, because if there is...

I dropped the under dash cover yesterday afternoon and put my hand on each of the relays and black boxes just to make sure none of them were 'acting funny'. All but one were cool to the touch and none were chattering or vibrating during the brief engine surges.

I'll also check for vacuum leaks in the process.

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Don
'85 500SL (Euro) - 186,000 w/a complete restoration and engine rebuild at 154,000
'95 C280 - 174,000