I have a 1973 450SL (EFI injected) which recently developed a miss at ide and all speed ranges. If I run the car for about 1/2 hour, shut it down and wait about a half hour, then start it up again, it runs perfect. This has consistently happened the last few times I've had the car running.

All the sensors, fuel filter, pressure regulator, fuel damper have been recently replaced. The injectors were replaced a few thousand miles ago. All the ingintion parts are new. Compression values were between 150-160 psi when I tested about 2k miles ago.

When I have this problem, I've noticed that the fuel pressure, 29 psi, fluctates about a pound or two while running. Should the pressure be absolutely steady?

Any hints as to where I should start checking?

THanks.

JP

I just started the car up for the first time in about 3 weeks. Now it will barely run!
I pulled off each injector wire and noticed that cylinders 3, 4, 5 and 7 don't make any difference in the way the engine runs. I don't think it's the trigger points since they are new and none of these bad cylinders are paired up in the points anyway.

Any thoughts?

JP