my 88 300 e runs good at speed on highway.,but runs rough at idle like it is hunting or fluctuating and sometimes stalls at idle! it starts good when cold and takes longer to crank when hot and has not been restarted for a few minutes.the 2 problems may not be related because the idle is bad hot or cold. thanx john............

John:
Welcome to this site.
Any warning light "on" on the dash, like maybe the abs light?
This topic has been covered alot, sounds like the overvoltage protection relay or possibly just the fuse in this relay has blown.
The overvoltage protection relay (OVP relay) is located behind the thin black panel behind the battery. Pull that panel out of there and look for this silvercolored relay with the clear plastic cover on top. Open that cover (like a lid) and there is a red 10 amp ATO fuse under there, check that fuse.

Gilly

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Hi,

Had similar problem on my 87 260E. The clue that I am going by is that it turns on fine when cold and difficult when hot. I am assuming that there is no fuel smell or fuel leak anywhere. Also it is not as trivial as fuel filter. Two parts may be involved. There is a fuel injector temperature sensor that tells the fuel computer how much fuel to send to the engine. It sits on the engine and is subject to very high temperatures, so chances are very high that it has gone bad and so when the car gets hot, enough fuel is not sent. It is a $40 part, I would change this the first. This fixed my car. If it still does not work, have a MB mechanic check the Fuel relay when the car is hot, the fuel relay may be bad and therefore your fuel pump is not working when the car gets hot. This is about a $100 part. Then the parts like fuel pump, fuel regulator and fuel computer get substantially more expensive, so they should be replaced only if you are very sure, for these items, you will have to get a perfect diagnosis, perhaps from a very good and patient MB tech.

Also as an immediate rememdy, in my case if I depress the gas pedel completely, the car would start right away. This may work for you too.

Good-luck,

Saumil

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Saumil S. Patel

thanx for the info. I have no dash lights on,no fuel smell.just a rough idle. ignition tune up no help .a vacum gauge showed 15" .idle is approx 500 when good. I can see no bad vacum lines with the air cleaner off.I sprayed lubricant on the injuctors but the idle did not pick up. I also cleaned the idle controll valve. no help.it has 175k milage. and uses no oil! thanx john

My 88 300E had the same problem. It turned out that it needed new injector nozzles.