Re: [T3] Idles on 2; runs on 4

[Elroyyy@aol.com]

>> She's a 1973 FI MT Squareback.
>> I ran the tune up; it consisted of an oil change, valve adjustment, plugs, 
>> points and condenser, adjust timing, check idle. This was not my first 
tune up. 
>> Everything was great for a little more than a week and then she began to 
run 
>> rough. At first, she just wanted her accelerator pedal feathered at the 
light 
>> to keep the RPMs up. A little later, she wanted the pedal tickled to keep 
from 
>> stalling. Eventually she would stall and I'd have to crank her over and 
over 
>> until she'd catch, blow petrol-smelling smoke, then continue.
>>
>> Since I'm an avid reader of the type 3 list, I knew immediately that if 
the 
>> car runs rich it must be a problem with the Voltage Regulator of the Cold 
Start 
>> Valve. I ruled out the CSV because I live in Southern California and the 
>> problem doesn't happen until after the car has been started.
>> So I connected my trusty VOM to the battery and got 12V. As the car 
>> approached medium RPMs, the VOM began to read higher and higher and 
leveled off >>just shy of 14V. But that's what it's supposed to read! The Voltage 
Regulator is not 
>> my problem.
>
>Make sure that the CSV wiring between the CSV and the temp switch has 
>not gotten shorted to ground. This can mimic cold weather. The best 
>way to eliminate the CSV as part of the problem would be to just 
>unplug it temporarily, as a test.

Yes, as a test, the CSV was unplugged.


>It's possible that your VR only goes bad as it warms up, so try to 
>take the car for a drive and then check the voltage after the drive.

A new VR was tested but the problem continued.


>> He tested a known-to-be-good Pressure Sensor and nothing changed. He 
cleaned 
>> the trigger points and nothing changed. He retested for spark -- it's fine 
all 
>> around.
>
>Is there any chance that the PS on this car is the wrong one. The one 
>for 70-1 has a couple of vent holes in the "cover" and these indicate 
>a style of PS which has a brass diaphram which can crack and leak. 
>The 72-3 PS came with a black cap over the adjustment screw, but 
>sometimes these have been broken off to tamper with that screw. You 
>really want one which hasn't been tampered with.

The PS is the right one. It's an "E" PS with an unmolested black cap.
Check the dwell and timing with a dwell meter and timing light?


>> But he discover that the injectors for 1 and 3 were spraying too much fuel 
on 
>> each impulse. This is particularly troubling because the paired injectors 
are 
>> 1&4 and 2&3. The injector wires were reversed on each side and 2 and 4 
>> started shooting too much fuel while 1 and 3 were fine. This tells me that 
it's not 
>> a problem with the injectors themselves.
>
>Yes, sounds weird. How did you tell this? It's hard to see this 
>visually, did he actually measure it? If this is true, I agree that 
>it sounds like a brain problem, but such problems are actually 
>exceedingly rare. Were these injectors all genuine Bosch?

The injectors are all Bosch 007 yellow injectors. The test was done by 
allowing the injectors to spray into a jar. Same thing was done after reversing the 
wires.


>> Next, he called to ask if I had another ECU we could try. The short answer 
is 
>> no. She's a 73 with an "E" system (brain, pressure sensor and throttle 
valve 
>> switch all match). The only ECUs I have are a "D" and a blank. There is no 
>> part number anywhere on the blank. So we tried them both.
>> The "D" brain didn't seem to affect anything. The blank, however, was 
another 
>> story altogether. Instead of pushing out too much fuel, this brain allows 
no 
>> fuel to 1 and 3 while she idles. But when she gets a little gas, she'll 
run 
>> fine on all four.
>> 
>> Personally, I don't think the problem lies within the ECU. But I'm open 
>> minded enough to consider it as a possibility. I have a spare "E" ECU on 
the way 
>> but it won't arrive until some time next week. Anybody have any ideas?
>
>I also have E brains here.

Thanks, Jim. I have an "E" brain on the way. I'll let you know if the one I 
get doesn't work.


>I assume you checked the hose between the intake air distributor and 
>the pressure sensor, just to make sure it hadn't fallen off.

Yes, checking that hose for a leak was one of the first things I did before 
taking it to the shop.

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