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1985 300d
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39 Posts
Discussion Starter #1
Fellow members I have a 89 420SEL with 90k original miles on it, thats got a slight miss fire at idle. It’s so slight that it won’t make the rpm or oil needle flicker or move but you can definitely hear (in the exhaust note) and some what feel it. Also it feels a little sluggish, won’t pull like a 91 420 SEL I had 20 years ago. I’ve done the basics, new filters, spark plugs, spark plug wires, dist cap and rotor, coil, EHA valve. Car doesn’t have a vacuum leak. I’ve changed the fuel pumps, fuel filter and fuel regulator. Seems like the po changed the fuel distributor at some point. All this service has helped but the car still feels sluggish. Sometimes it feels like it’s got good power and pulls good other times it feels like it’s bogged down. Any clues as to what I could check next? The car does not have resonators and is catalytic converters delete, the O2 sensor is still in place. Could it possibly be the EGR valve maybe, by the looks of it, it appears to be the original EGR valve on the car.
 

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Registered
1985 300d
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39 Posts
Discussion Starter #2
Update. The rpm when observed very closely seems like it’s varying in a rhythmic manner by 100 rpms or less. The car idles at the normal range but seems like its oscillating by a very small amount, not even 100 rpms to be honest.
 

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68 250S, 91 300se, 98 SL500, 450SEL 6.9, 14 CLS550 Past MB's; 300SD, 300E, 300TE, 190E, ML420
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4,167 Posts
You should be asking in the W126 forum. Did you use genuine Bosch cap and rotor? Have you adjusted the Fuel Distributor yet? Make sure you know what you are doing before even touching it.
 
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