I let my daughter use my 87 260e 270K on the clock for a couple weeks. She called me up and said that when she goes to start the car that it revs up and she shuts it off. I go over to her house to check it out and it fired right up for me so i drove to her work and dropped it off. It started up fine for her to get home. The next day it does it again and she sends me a video of it firing up and going straight to redline. A couple of days later I go pick it up and it fired up fine for me. I have it in my garage now and cant get it to reenact the redline problem again. I cleaned and oiled all the linkage and will see what happens.

Has anyone came across or have heard of this happening? Ive gone thru this in my head and cant figure it out. Possible VAC leak or fuel leak into manifold. For it to be so sporadic is what is throwing me for a loop.

I'd suspect that the throttle linkage is sticking partially open. It doesn't take much for an unloaded engine to race to redline. Solely a fuel leak would cause flooding, solely a vacuum leak would cause an excessively lean condition, and it would have to be pretty massive. For it to make it all the way to the redline, air has to be passing through the throttle plate for the CIS plate to meter fuel.

That's my thinking anyway. It's not unheard of to have the overly-complicated linkages stick or bind up.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Is she on the pedal when she hits the starter? It doesn’t explain what’s sticking but it might explain why it happens to her on startup but not to you.

Have you ruled out a bunched up floor mat?

Sixto
98 E320s sedan and wagon
02 C320 wagon

Thanks for the reply's fellas! Unfortunately the problem is still there. In fact this morning I went to fire it up and it started up fine. I get out to walk around to the passenger side and it jumped straight to redline when I was in front of car. It bounced off the rev limiter about 8 times before I could get it shut down. Now im very confused on what the problem is or can be.

Detach the cruise control actuator and see if it happens. Disconnect the throttle cable/linkage at the engine and see if it happens.

Sixto
98 E320s sedan and wagon
02 C320 wagon