Hot Idle Problems Help Options

[McMark]

Sorry for the long post, but I wanted to be clear. (IMG:style_emoticons/default/biggrin.gif)

I'm having problems with hot idle. My car is a 73 1.7. Same old story, it runs fine before it warms up, but then it won't idle. The weird part is that if I pull the plugs on the injectors one at a time, pulling 1 or 3 will kill the engine before I can plug it back in, but pulling 2 or 4 will just lower the idle to almost dead levels. And even then, 4 seems to have less of an effect than 2.

1. Trigger Points
My trigger points seem to be working okay. I checked them with my oscilloscope and got a nice square wave pattern on both contacts.

2. Air Temp Sensor
I usually run with the air temp sensor unplugged, since plugging it back in gives worse performance while the engine is warming up.

3. Head Temp Sensor
Replaced with a new unit from Napa Auto Parts. Measures at 70~80 ohms hot. Does this seem low?

4. Hoses
I have unhooked the vacuum retard and the decel valve. Both are plugged off. I wouldn't expect this type of behavior from leaky hoses, because it is my understanding that leaking hoses cause a high idle and not a lean/rich condition.

5. Fuel Pressure
Checked to be at about 28 psi. I was reading something about kinked lines causing problems. Could a kinked line give correct pressure, while lowering delivery rate? Or would you notice a pressure drop if you drove with your guage connected so you could see it? If there's a problem, could fuel pressure change under load, and look fine at idle?

6. Ground Connections
I spent about 1.5 hours cleaning the engine ground connections about 3 weeks ago, so I hope there isn't a problem here. Has anyone used dielectric grease on ground connections to stop corrotion and give a better ground?

7. ECU
Part number: 0 280 000 037
Also, 022 906 021E

8. MPS
Calibrated to '73 1.7 standards by our own Jeff Bowlsby. Tested to be in acceptable condition.

9. Valve Adjustment
I adjusted the valves last week. All the valves measured to be in very good adjustment before I changed anything and the car ran about the same before and after.

10. TPS
Recently replaced witha new unit from Pelican. Seems to be adjusted correctly, idle circuit is on when throttle closed and breaks when openening the throttle only a tiny bit.

Well, that's all I can think of right now. Any ideas?