Suddenly, Things To Talk About

The next step in diagnosing my full-throttle misfire issue was to try a guaranteed-to-work loaner EHA (Electro-Hydraulic Actuator for the fuel injection system).

The CIS-E fuel injection system is really finicky in places and although it's commonly thought you will see or smell a fuel leak when the EHA fails, this is not true in all cases. You may have a perfectly fine looking EHA with great O-rings and still you may have misfires at various RPMs and throttle positions. This is because your engine will be receiving more, or less fuel than is appropriate for the situation at hand. None of it may end up outside the EHA or the fuel lines but it is surely ending up in the combustion chamber and that would cause a misfire.

I happened to have a working EHA available, so I gave it a go in my car. It's a simple job: remove air filter casing, disconnect the electric connector on the EHA, remove two bolts that hold it in place, and it will drop in your hand. The only things you need to pay attention to: some fuel will spray uncontrollably because the fuel lines are under pressure, and the little rubber O-rings between the EHA and the fuel distributor may drop and get lost.

Sadly, switching out the EHA made no difference to the misfires I'm experiencing. I still have an idle misfire when engine is slightly warm but not up to full operating temperature, and a consistent misfire/hesitation under WOT acceleration. This is where I currently stand in the diagnosing:

• Spark plugs
• Spark plug wires
• Distributor cap and rotor
• Fuel/Air mixture
• Fuel filter
• Fuel pumps
• EHA
• Fuel pressure regulator
• Fuel accumulator
• Ignition timing

So, next up will be the fuel pressure regulator, and fuel accumulator as suggested by Dr. Greene earlier in this blog. The accumulator is not expensive, only about 100 EUR, but the pressure regulator is many times that, so I may have to wait again until I find a working loaner.


Despite the misfire problem I couldn't resist taking the car to the strip yesterday. I had beaten my friend's 560 SEC ECE in the dynamometer, and now, with him having replaced his EHA, it was time for a rematch in an actual performance arena.

Having lined up at the start, I put the gear selector in "2 B", and then back to D. This will ready the gearbox for a first gear start in a European W126 car. Consider this "launch control" from the 1980s... Otherwise the car will always start in 2nd gear, for smoothness, even in S-mode. Speaking of, I had the gearbox in S-mode, which will allow the engine to rev to the redline, unlike the E-mode which will shift pretty early in comparison.

I stood on the breaks, built some revs until the car was eager to go, and made my start. Accompanied by two(!) long black lines and some tire smoke from my cheapo tires, I made the quarter mile in 15,39 seconds. In 2011, I had achieved 15,37 seconds. As the car stands, I believe it would do under 15,3 seconds, if not for the "showy" start.

There are some US websites listing 15,2 second quarter miles for 560 SEC cars, which may be on the less powerful US version. With the misfire fixed, I believe mine could do a sub-15 second quarter mile.


And an announcement: 320 000 km, last Thursday, congratz car!

This will mean a scheduled service. This time around, engine oil and filter, and power steering fluid only.