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Old 02-26-2002, 08:54 PM
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MikeTangas MikeTangas is offline
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Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
Cold miss/hot miss M117

This is on the 560SEL.

I had a very slight miss at cold idle, also noticed after yesterdays highway run I have a miss at hot idle too..

I decided the cold miss was ignition timing. Book shows I can set timing without vacuum to between 3-7 BTC, which should yield 12-14 BTC with vacuum. Soon as I got home from work I disconnected the vacuum line to the EZL and attached my vac gauge and timing light. At cold idle was pulling 15" HG, and timing was about 10 BTC. I adjusted timing without vacuum to 5 BTC (can't get much closer to the split of 3-7), vacuum increased to 16" HG. I reconnected the vacuum to EZL and checked timing, and it is now steady at 13 BTC idle, 44 BTC at 3K rpm. Miss at cold idle is gone. Vac gauge applied to the air pump vac line shows 17" HG at idle.

Now for the hot miss. I want to ask if the miss could be temperature dependent? After running 20 miles yesterday, the temp was only about 40dC (but <50 dC). At less than 50dC, the thermo switches don't open to redirect the vacuum. Could a cold running engine cause the hot idle miss, or could it be a combination of the time being a shade off plus the cold temp? Am I even on the right track?

Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon least its a diesel

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