It could be ignition related or fuel related. Tough to make a recommendation without knowing more about which system is at fault. Having said that, The fuel pump relay on this generation W124 can go wonky. They usually stall the engine though and don't recover until you power the car off and on again. Check it anyway. It would make sense to check all of the connections at the battery, clean the fuse holders in the fuse block and install the copper type fuses, ensure your connections at the coil are tight, and fuel pump as well.

A good friend who will remain nameless sent his priceless 288 GTO out to a well-known Ferrari shop in Wisconsin TWICE to solve an intermittent power issue. He spent as much on shipping the car back and forth as some of us spend in total owning our W124s. Each of the two trips didn't resolve the intermittent issue. One day the intermittent problem finally went completely Tango-Uniform. He now had one dead bank on the V-8 and he and his general mechanic were chasing down possible ignition issues. I happened by and joined in the fun. They ran the car and demonstrated for me that the bank was dead. They were swapping out all sorts of ignition components from the left bank to the right one, and so on. I pulled a plug and it was dry. Clearly there was no fuel getting to that bank. The pump also was not running on that side. I slightly tugged on the wire to the driver's side pump and it came off in my hand. A simple recrimp and the car ran perfectly again. So don't overlook anything.

 

Thanks for the suggestions. In August of 2018 I cleaned fuse holders and replaced all fuses with new ceramic ones. The car had total loss of power on 2/6/15 at 80 mph. It happens sometimes

 

An after market fuel pump did this to me and also stalling the engine at lower speeds. It started acting up after like 6 months.
I think a shorted fuel pump (direct connection that keeps it always run the pumps) is easy to find for a test. I keep my shorted original part for this (if I'm using "shorted" the right way).

 

 

After it lost power momentarily at 80 mph in 2015 I changed both fuel pumps. One of the fuel pumps was leaking.

 

Would help to know if the loss of power was soft or hard.
Fuel is usually soft and electrical is usually hard.
IE did the power drop then come back sharply, with a jolt or fade out and fade back in?

 

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Would help to know if the loss of power was soft or hard.
Fuel is usually soft and electrical is usually hard.
IE did the power drop then come back sharply, with a jolt or fade out and fade back in?

 

It is like you have bought gasoline with water in it. The motor is running very smooth up to that pause. I would consider it more towards soft. It only happens on Interstate around 80 mph. After a few seconds it continues like normal.

 

Ever managed to short this out?

 

The radiator failed and the antifreeze went to the transmission. It turned the transmission fluid the color of Pepto-Bismol (pink). I didn’t realize what happened and it ruined transmission.