Fuel Injectors

[Pengue]

Generally my '71 280 SL runs great but after sitting and idling for a period of time (5 minutes or so) it will stumble fall over itself when I accelerate.  Feels like just clearing excess fuel that may have built up in the piston chambers.  After 30 seconds or so of running very rough it smooths right out.  Could this be the fuel injectors?  I was thinking about having them pulled and doing a bench test to evaluate the spray pattern.

Any thoughts or similar experiences would be appreciated and what was the corrective action.

[ctaylor738]

Before going after the injectors, I would check the idle mixture and adjust as necessary, and make sure the car has non-resistor spark plugs, like Bosch W7DC.

Cheers,

CT

[Pengue]

Plugs have < 1000 miles on them and are Bosch W9DC.  Part # 003 159 1003.  Got this info from Gernold at SL Tech in Maine.

[Peter h]

w9DC may be a bit too high.
I would also try w7DC or w5DC
What is the color of the spark plug?
Peter

[lurtch]

I would ditch the Bosch plugs, I did so years ago and went to NGK's. Never going back.

Larry in CA

[JohnnyC]

I too ditched Bosch plugs years ago with my other cars also. My preferred is NGK (BP5ES for the 280SL). My first choice with all my other cars also.

Cheers and God Bless,
JohnnyC

[rwmastel]

Generally my '71 280 SL runs great but after sitting and idling for a period of time (5 minutes or so) it will stumble fall over itself when I accelerate.  After 30 seconds or so of running very rough it smooths right out.

Would spark plugs cause an intermittent problem like this?  I would assume if the plugs were a wrong, they would cause a more consistent issue/symptom.

[rosch]

I would first do a quick check on the mixture at idle  by doing the split linkage test.
When your mixture is rich at a longer idle period this may foul your plugs ,especially right after a cold start when your plugs have not reached their optimum working temperature.. Running your engine at a higher rpm will often clear a (light) fouling after a short drive. Use the correct heat grade non resistor sparkplugs. NGK BP6ES generally work out nice. NGK BP5ES are slightly hotter and are recommended when (light) fouling occurs during normal operation .
Observing the color of your plugs tells you a lot about your mixture.
Tip : mixture and ignition problems  are easier to diagnose by using a so called Colortune (just google it).
This way I found a leaking injector causing me a lot of headaches over time. Mixture checks at any rpm and adjustments are easy to accomplish as well.