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.

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  • Mercedes-Benz Master
  • 5,627 Answers

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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Posted on Jan 02, 2017

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  • 11 Answers

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

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

Posted on Apr 27, 2009

lastech
  • 408 Answers

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

  • 1 Answer

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

  • 2 Answers

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

alicantecoli
  • 22484 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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Does a 1988 mercedes benz 560 SEL have fuel injection?


Yes. It uses a bosch CIS-E injection system. More information about the system can be found here - http://en.wikipedia.org/wiki/Jetronic

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Bad fuel economy and lumpy idling - possibly causes


<p><b><u><span>Excessive fuel consumption and 'lumpy' idling engine</span></u></b><br /> <p><b><span>Possible faults:-</span></b><br /> <p><b><u><br /></u></b><br /> <p><b><u><span>Coolant sensor </span></u></b><span><span> </span>- engine is signaled as being 'cold' all the time, not just at start up, causing ECU to set longer injection cycle </span><br /> <p><span><span>&oslash;<span> </span></span></span><span>Low coolant level can prevent sensor being able to detect coolant temperature</span><br /> <p><span><span>&oslash;<span> </span></span></span><span>Faulty 'open' thermostat allows coolant to circulate without regulation and perhaps prevents the engine from achieving normal running temperatures.</span><br /> <p><span> </span><br /> <p><b><u><span>FPR</span></u></b><span> - broken diaphragm allows fuel to enter the vacuum line and then into the inlet manifold. Additional source of fuel makes the fuel air mix richer causing a faster and lumpy idle.</span><br /> <p><span> </span><br /> <p><b><u><span>Vacuum leak </span></u></b><span>- 'high oxygen' signal from O2 sensor causes ECU to set longer injection cycle.</span><br /> <p><span> </span><br /> <p><b><u><span>O2 sensor</span></u></b><span> - 'high oxygen' sensor error causes ECU to set longer fuel injection cycle</span><br /> <p><span> </span><br /> <p><b><u><span>MAF</span></u></b><span> - 'over reads' in error the amount of air entering causing ECU to set longer fuel injection cycle </span><br /> <p><span> </span><br /> <p><b><u><span>IAT</span></u></b><span> - 'under reads' in error the temperature of incoming air causing ECU to set longer fuel injection cycle</span><br /> <p><span> </span><br />

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I have problems with my 1999 mercedes-benz ML320. minutes after ignition, when driving at low speed or high speed acceleration note failure. push the accelerator pedal fully and have no adequate response....


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1 Answer

Cold start


Duty cycle needs adjusted, screw in middle of air cleaner assembly leads to it.

Also the fuel distributor may not be allowing fuel in at cold start like it should but until duty is set i wouldnt mess with it.

To set duty cycle its kind of drawn out to put here.

I suggest hopp on over to benzworld.org as they have some great guides and how to's.

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1 Answer

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engine wiring harness upper and lower could be degraded, coil could be bad, throttle positioner, fuel distributor could be bad and depending if its a half year car and you have an OVP that could be bad. Also after a full tune up have someone adjust the duty cycle.

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My 1995 S500 Mercedes Benz is idling very rough. It runs great while driving but idles very rough. I have changed the spark plugs,wires,distributor cap,had fuel injector cleaned by a pressurized...


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