Thanx, Ruben, for the update. I'm still very curious.

Too bad all those hoses are in the back. CIS cars just have a lot of hoses and devices (other current threads are dealing with various problems wiht those devices). Removing my engine did a lot to help orient me as to how the engine is configured. Those little mirrors with long handles must be in every Porsche mechanic's tool box.

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'83 SC

I just removed and replaced the engine in my '83 SC last week. I was very, very careful to label all the vacuum lines and so on, to make sure stuff went back together exactly like it was before. After putting the engine back in, I was anxious to fire it up. It did fire up promptly, and idled around 900 RPM. Then, after warming up a bit, the idle came up to its usual warm idle speed of 1100 RPM. I was smiling at this point, because this is how my car was behaving before I took it apart.

A few minutes later, the idle increased to about 1400, and then to about 1600 a few minutes after that. It never went higher than 1600. My smile disappeared. I immediately started questioning my thoroughness in reconnecting things correctly.

I then mentally stepped through everything I had touched, to see if I had done anything which might have affected the idle speed. I looked at all the vacuum connections (at least the stuff I could see), and I fiddled with the mechanical linkage stuff for a long time before finally convincing myself it was OK.

I then remembered that I had made a patch to my oxygen sensor wiring as a final step in the reassembly. Before removing the engine, I noticed that the oxygen sensor wire going to the car from the engine bay was broken at the orange connector thingy. So as part of my repair work, I resoldered the wire going into the male end of the connector, and plugged it back into the female part of the connector, which comes from the sensor. This is what caused my high idle speed. When I let the car warm up, with the O2 sensor connected, the idle speed is 1600 RPM. If I then disconnect the wire, effectively returning my car to its previous sensorless state, the idle drops immediately down to its "normal" 1100 RPM. This may or may not be related to Ruben's problem, but it's worth considering.

Now I need to do a little research to determine if my O2 sensor needs to be replaced. I think that somebody broke that wire a long time ago, which affected how the car idled, so somebody turned up the idle speed. So when I came along and reconnected the sensor, the idle adjustment was all wrong. Or perhaps the idle speed is wrong not because the idle was adjusted, but because the sensor is putting out bad values. I measured a steady voltage of 0.06 coming out of the sensor connector. If memory serves correctly, that's way too low.

But I can also see how a mechanic unfamiliar with Porsches would try to drop the engine without removing the throttle linkage rod between the tranny and the engine. Doing so would definitely break something (or at least bend something severely).

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Greg Slater
1980 SC
gslater@uswest.net

I'm still curious.

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'83 SC

Curiosity killed the cat.....
Perhaps the problem lies in the catalytic converter reinstallation??

(ridiculous literary/engineering almalgamation, useful only in that it has reinforced my decision to call it quits for the day, go home and eat some food).

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'72 911 TE

Hi guys, I'm still here. I'm in the process of replacing my old PC which chrashed this week so I have been busy shopping around for one. I will continue my investigation on the idle problem on Saturday. Luckily its been hot here in Florida so I'm driving around with the air conditioner on and this lowers the idle rpm to 1200 rpm. Greg, where is this oxygen sensor located in the engine bay? I like to take a look at this connection also. Thanks to everyone again for the support and suggestions.

Ruben
1976 911 2.7L

My car has an O2 sensor but earlier SCs do not. I suspect yours does not. If it does, this would make it easier to check mixture.

Ruben, we have been assuming that your mechanic reinstalled something incorrectly and I think that's a good assumption. Of course, we still need tu understand his "welding" comment as well.

But having said that, there is a procedure in the Haynes manual for checking these 'auxiliary' air devices. It is in the "supplement for later models" section near the rear of the bood, under 'fuel and emissions.' the paragraph is labeled, somethingabout a "choke' or "automatic choke." (My Haynes is downstairs) Anyway, it explains how to test them to see if they are working, and also provides some CIS vacuum hose diagramming for various SCs, which could be helpful to you.

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'83 SC

Then again, if your idle adjusting screw is all the way in, and the engine runs, there is more wrong than just a faulty Auxiliary Air Regulator or Auxiliary Air Valve.

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'83 SC

Oops! I should have noticed that Ruben's car is a '76, therefore, no O2 sensor. Silly me. But I will state that I'm kind of enjoying having one, since I've spent the last several evenings in the garage fiddling around while my car is running, watching the mixture change as indicated by the sensor.

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Greg Slater
1980 SC
gslater@uswest.net