Motor not stopping on ignition off

[iancass]

My '87 3.2 911 sometimes runs on after the ignition is turned off.

It has about 120K miles on it and uses absolutlely no oil.

I'm about to carry out a standard service (plugs, valve clearances etc) for the first time (my first time not the car's!) and am wondering if there is anything else I should check?

[Joe Bob]

Puttt, puttt, run on or full engine running with all the gauges and lights dead?

[iancass]

phut, burp, fart etc. Never for more than 2-3 seconds but that feels like an age when your pride and joy sounds like S**t. Lights etc are shut down by the ignition off.

[Joe Bob]

That's dieseling....could be timing or fuel mixture or a leak in the exhaust.

[Doug Steinel]

When you say it stays running with ignition off:

1. does it chug along for a few seconds and then die? If so, it is dieseling.

2. does it keep running as if the ignition is on? In that case, your talking about a problem in the ignition switch, which I have had.

[911S77]

could be dme relay under your seat - check it...

/Jack

[iancass]

Chugs along for a few seconds - So sounds like dieseling. Hmm - what do I do?. fueling was recently checked and okay. What else can cause this?

[Doug Steinel]

Some immediate things to check. Do you have a timing gun to check the ignition timing. All the standard books and this forum have instructions on how to do this.

Alson, try using a higher octane gas