Question about Mercedes-Benz S-Class

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I have a mercedes benz W116 280 SE USA version from 1977 with K Jetronic fuel injection. Engine is running to slow and unstable at idle. What do you suggest me to check ? car has 64,400 original miles and has new engine air filter, oil and oil filter, air pump, gas filter, 4 new engine belts, and I have just driven it for a 850 miles highway trip with no mechanical problems.

Posted by jmf26 on


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Vernon Taylor

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It has been a long time but I seem to remember the K Jetronic is adjustable but the adjustments are normally sealed from view. I don't have the information to hand.

I also seem to remember the system used a separate enrichment device for cold starting and warm up which could perhaps cause idle problems if it isn't working correctly.

Considering the age of the car it would be wise to employ best practice and examine the basics first. Clearly considerable maintenance has already been carried out but you didn't mention a general tune-up where the ignition timing and valve clearances are checked, the engine breather, throttle body and fuel distribution metering unit is cleaned.

It would be well worth checking for intake air leaks especially through the brake booster. If the intake valve seats aren't in virtually perfect condition each combustion can leak into the intake manifold and cause the next incoming charge ineffectual. Only a cylinder leakage test can diagnose this.

If no other fault is found the quality of the injector spray pattern must be tested. If an injector isn't spraying correctly and the engine is running too slowly for the incoming air to break up large fuel droplets the burn will be impaired and although it will behave as a weak or lean mixture, much still burning fuel will be expelled through the exhaust valve.

Posted on Sep 02, 2017


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SOURCE: '89 benz 300e, hard to turnover when starting, fuel pump/filter?

Run some Sea Foam Through it you tube sea foam It works

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manuel domingo

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SOURCE: does the mercedes-benz 1986 mercedes 560 sel have

hello, 560 sel,,,model 126.039 engine with v-8,engine number 117.968 ke is is fuel injection system.ref. book;technical data mb,ty

Posted on Apr 29, 2009


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SOURCE: 2003 Audi A4 1.8T Check Engine light on

mine was related to the gas cap not sealing, a cheap fix
03 a4 avant 1.8t

Posted on Jun 16, 2009


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SOURCE: '07 Tahoe; check engine light on steady. Just came

Have a dealer or garage check your Oxygen (O2) sensor. As a quick fix, try disconnecting and reconnecting your car battery. Sometimes this will reset the check engine light.Good Luck!

Posted on Aug 01, 2009


Colin Stickland

  • 22485 Answers

SOURCE: 1980 VW rabbit, manual/fuel injection: I am

it starts from cold because the auto choke is on ,allowing a richer mixture ,try removing the sender unit in the tank and seeing if the connection from the pump to the outlet connection is ok or leaking causing a loss of fuel pressure

Posted on Aug 02, 2009

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