Idle isn't quite right, Blah. Options

[corsepervita]

Well, installed new points, set dwell, set timing to 27btdc.

The car runs better than it ever has and it feels fantastic. Of course, it's still a bit cold blooded till it warms up and finicky till warmup temps arrive.

The car has never quite had a perfect idle. After setting the dwell and timing, I decided to try the idle screw, which had absolutely no effect on the idle at all. In fact, I could entirely remove it and it did nothing.

Here is a video of the car idling.

I mean the car runs smoothly. It accelerates fine. It feels fine. The Idle is low and doesn't seem to care whether or not I adjust the idle. It literally just sits there where you see it on the tach. It starts this way and runs this way hot or cold. Obviously after the car exists high idle, but high idle works fine.

(Original injection, not carbs)

I will clarify, this did not change after I set timing and dwell, the idle has been this way for a while and has not changed. Even after new vacuum lines, injector seals, fixing vacuum leaks I could find, it has not changed. Someone some time ago mentioned mixture and to try a small correction on my ECU. My ECU does not have a POTs system on it, so I cannot do that, it's an early '70. Which also baffles me as to how one would "change the mixture" if that is the case.

[corsepervita]

Intrake leaks will result in a high idle, not a low one. Unplug the air temp sensor in the intake plenum and see if that helps. Pull and hold a vacuum on the MPS. Check the hose to the MPS. Adjust the valves, tight valves can cause a low idle speed. Check and set the point dwell. Set the timing, hoses off and plugged. Check the fuel pressure while the engine is running. 29 PSI is the goal. Report back.

The Cap'n

Alright... so here we go... I finally got some time today to work on this.

Hose to the MPS is new. MPS is also a rebuilt unit (replaced the previously bad MPS I had). Although the numbers are not the same. However, car idles the same with bad MPS or new rebuilt MPS.

MPS will hold vacuum with no issues.

Valves were adjusted to spec less than 1000 miles ago, car ran more smoothly but idle did not change.

Dwell is set and is at a happy 47.

Timing set to 27btdc.

Do not have equipment to test psi, however, I pulled plugs and the mixture is LEAN. Not RICH like I thought previously.

After setting the timing, the idle was still funky. I decided to disconnect the hose for timing retard and suddenly..... the idle became normal and the car would actually react to the idle air screw and the car could be set to 800rpm idle.

(IMG:style_emoticons/default/WTF.gif)

Now, regarding Cabinet Maker's previous post... I went ahead and pulled the sensor and indeed, the resistance was where I found it earlier when things were "kind of warm" - I guess I did not wait long enough because after I took the car for a long drive, the resistance was about 50-70ohms, not 2200.

I went ahead and heated up the spare sensor I have with a heat gun and sure enough, it also went below 100ohms as it should.

I emailed Jim (Previous owner "Porsche Rescue") and he confirmed that he replaced the sensor when he gave me the description of the sensor he replaced.

So at this point I am leaning less towards mixture and more towards timing or something else. The plugs weren't ridiculously lean, just a tad on the lean side. With the previous MPS it was so rich the car would load up and just die. It will remain idling, but when hot, will pop a bit if you give it gas just barely at very low rpms. If you let off the gas at higher rpms you get a decel pop pop pop which if I am reading correctly is indeed a "lean thing"...

So I guess I was reading into this improperly.

I appreciate everyone's help.

At this point I can at least confirm:

- Car is LEAN, not rich, as previously thought
- Idle smooths out and will actually react to idle air screw when dizzy retard is disconnected, if it is hooked back up, the idle turns to crap and the car runs terribly again.
- Sensor for CHT is within spec when previously thought it was not, is under 100ohms at running temp

I haven't fixed it yet, but damnit I'm tired and I want a beer. (IMG:style_emoticons/default/beer3.gif)

PS: Part # off my MPS is 0 280 100 049