Help with diagnosing high revving engine on start?
 

I turned the key to start the engine on my 1984 911 Targa early this morning and the engine revved as if I had the accelerator pedal floored. I wasn’t expecting that result, so it took me a close to a second before I turned the engine off. I then reached down to the gas pedal to see if there was a problem I could solve by pulling on the cable and then started the engine again but this time I was ready to turn the engine off immediately. There was the same high revving issue, so I shut it down ASAP and went to plan B – taking the other car.

Any suggestions as to what to look at this evening?

Check for throttle operation at the other end of the cable. A broken cruise control unit caused a similar issue in my case. If you dont have another set of feet around, use a brick or rod to operate the pedal and check for proper operation at the intake.

Chip, I'll have some time this weekend to stop by and help you take a look.
I guess it could be the throttle cable and all, but maybe also the idle control valve could be stuck open. Might just need some Dorki TLC / Cleaning.

What's your schedule like?

I suspect the return spring under the drivers side runners parted ways. Bitch to connect but do-able.

ARF

Thanks for the ideas and offers. I will be back to all of you, thanks. I was working on another list of things to do today (a honey do kind of list) and we're leaving in about 10 minutes for a friend's 50th birthday party.

In the 30 seconds I've had to look at it with my wife depressing the gas pedal with the engine off and me looking in the engine compartment I see pressing the gas pedal does not move the throttle cable in the back. Broken cable?

It's not a cable, it's a metal linkage. Basically a bunch of rods with ball joints connecting them together. Something is wrong in the linkage. If the linkage itself just broke, the throttle would snap closed from the two return springs found on the engine. Possibilities are:

1. Linkage is broken AND jammed somewhere, holding the throttle open
2. The return springs are broken, so the linkage is all but useless without the return spring tension.

You're in Darnestown, so I can drop by and help out for a bit if you want tomorrow. Send me a PM if you'll be around and have some time.