300Sdl intermittent idling spike/drop-off

Now let me try to clarify what the car is actually doing. Normally the problem tends to occur soon after start up. The car starts ok, but during warm up the engine seems to rev up,maybe 1/2 second or so then it seems almost like the engine is going to die, then the motor smooths out and runs ok. The problem also has occurred when the car has been driven and has reached operating temp, the engine cut-off for a few minutes for a brief stop then re-started, and bam you may or may not experience the problem.

[Benzmac]

If it is a later 300Sdl, you should check the overvoltage relay, also, be sure that there are NO fuel leaks so air can get in.

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Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Donnie thanks for the input. I am not sure of mfg date of vechicle, but it was placed in service 4/86. Also, where is the overvoltage relay located? Is the test process simple enough for a DIY person? If the relay checks out ok could I possibly have an injector or injection pump problem?

Donnie, the OVP relay was the problem. I replaced the relay and the car idles without the intermittent spiking. Thanks for the help. Johnny

[Bill Wood]

Thanks for the followup message!
We really appreciate it when people close the loop and let us know what eventually fixed their problem.

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Bill Wood - Webmaster
MercedesShop.com, LLC
MB Autowerks Inc