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Rough idle @ economy guage not working 420 SEL
I lent my 1988 420 SEL to my father inlaw and when I got the car back the idle was rough. He had filled the car with gas so my first thought was bad gas. I have already run Three quarters of a tank of new gas through the car and it is still idling rough. I also noticed that the economy gauge had stopped working. Could a vacuum leak cause a rough idle?
Thanks Dave Schwartz |
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Most certainly.......
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Absolutely! and you can start your search from the line for the Economy gauge. A hand-held vacuum pump and digital multimeter are the most valuable tools I have for my MBs. Look in the manuals on the W126 CD-ROMs--there are good vacuum diagrams there. Cheers, Andrew Seidel.
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86 560SEC 85 500SEC Lorinser 83 300D Turbo 75 240D |
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Ok here are some things to check. You will find a small vacuum line running from the back of the engine to a small rubber "Y" connection just in front of the fuse box. It is usually strapped to the large black vacuum line going to the brake booster. One of the connections goes to a yellow vacuum check valve that has 3 connections on it. One of these connections (on the Y connector) goes to the line leading to the economy guage. Check these vacuum circuits carefully. I have seen the Y connector get hard, start leaking and generally fail. This would cause a vacuum leak and affect the mixture of the engine. Also check the vacuum connection on the back side of the engine for leaks or broken parts.
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I got too many cars!! Insurance eats me alive. Dave 78 Corvette Stingray - 3k 82 242 Turbo Volvo - Manual - 270k 86 300e 5 speed manual - 210k 87 420sel - 240k 89 560sl - 78k 91 420sel - 205k 91 560sel - 85k 94 GMC Suburban - 90k 97 Harley Davidson Heritage Softail - 25k 00 GMC Silverado 1 ton 30k |
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