Barn find. sat for a number of years full of gas. had to replace fuel pump and filter. hard starting. have to crank a long time when it does start runs rough for a bit then idles up to 1500 and wont idle down.Drained all gas and filled with 91 octane. what could make it act like it is? also put in new spark plugs. Really sharp car if I can make it run. 250000 miles, don't smoke. any ideas?

My bet would be vacuum leak .Check all small pipes and the conectors for splits. Under the air filter you will see a part with a conection on the rear ,its held in with a saddle and 2 screws ,on the rear it will have 2 hoses remove them and wash it out with white spirits or carb cleaner Then replace it .Also the top of the throttle plate ,spray this also with carb cleaner.. Next check all fuses ,the ends go white with corrosion and dont make contact. Give them a twist in the holders .Then all earth points want cleaning 90% of electric problems are earth related.Remove them clean and a little grease on the end , now pop the screw back in the end and lock it up. Come back after you have done this. As i now a few more things you can try out . One thing first ,spray the top of the injectors seals with Wd40 fluid see if it changes the speed of the engine..If so the seals have gone in the fuel injector seats .

Check the overload protection relay.

Check nearby threads on hard starting/rough initial running issues.

Duke

What to do when my M103 is giving me trouble: A beginners guide ~ Artisan

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Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....