My 1985 528e sat for 6 1/2 years when I got my hands on it (for $1) and I had the exact same problem. I didn't check my compression at the time, but deduced #5 and 6 were the culprit. I ran one can of BG44K through and got #5 back. Did it one more time and got #6. Runs great now, and didn't have to pull the injector to have it cleaned. Around here, Northern VA, the cost is close to $20 per can, but worth it for me.

Good Luck!

Jeff

I bought a 528e which has sat unused for almost 2 years.
The car was running perfectly prior to being parked for this period. I know this for a fact.

The car only runs on 4 cylinders now at idle (1-4) and 5&6 are both "dead" (pulling plug wires makes no difference to the idle).

The dead cylinders are getting a great spark, and the cap and rotor appear fine.

I first swapped the spark plugs, but the problem remained with 5&6 cylinders.

I then pulled the valve cover to verify that the valves were not sticking open, but the valve clearance was correct.

As a back-up I did a compression check, thinking that 2 dead cyl next to each other could mean a bad head gasket. Compression was 175-180 psi on all cylinders, so no problem here.

Fuel pressure is good.

All injectors are clicking the same (checked by holding a screwdriver to injector body and ear and all activate audibly and the same).

So what gives?

(Personal opinion is that the 5&6 injectors may be fouled and despite clicking away are not discharging fuel, but I would solicit your suggestions before I try extracting the uel rail and injectors from underneath the intake manifold runners on the eta engine (Pulling the fuel rail on the M30 big six is a piece of cake compared to working under the eta manifold runners).

Thanks in advance for all suggestions
Bob