My 87 260E started having cold start problems. I took it to the dealer where purchased, my independent mechanic retired 1 month ago! The plugs, cap, rotor and overload relay were replaced. The car starts ok now, but now I have new problem the car bucks at highway speeds. It feels like the fuel supply is momentarily cut off. This only started on the way home the shop. The car never did this before- 176K miles! Please help with any suggestions. Could the new relay be defective, or bad fuel pump, or accumulator. I am bringing the car back tomm, but would like a heads up. I am afraid to drive it.

I have had a few faulty over voltage relays out of the box.

One thing I have seen is where the relay is faulty for a while and it kills the o2 sensor. When this happens and the new relay is installed, the fuel system is now working and trying to compensate. I would have checked the fuel mixture before letting it go out the door.

Also, have the fuel pump relay checked.

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Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
OWNER OF MB AUTOWERKS .COM

Thank Youfor your reply. If the O2 sensor is now bad, should the O2 light be coming on?

FYI After having the overload relay replaced again and then the fuel pump relay, the car was still bucking. After three weeks in the shop and numerous other attempts, the engine temp sensor was replaced and that has corrected problem so far. Thank You - this is a great site!