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Wayne 962 Wayne 962 is offline
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Still stumped - 959 Fuel Injection problem...

Here's the original thread:

Frustrating 959 Problem -> Need suggestions...

I now have more info. I'm pretty convinced that this has nothing to do with the fuel, that the gas station thing was just a coincidence. The problem is that the computer is sending a signal to close the Idle Control Valve (ICV) when it shouldn't be.

I unplugged the ICV from it's electrical connector and the car starts and idles pretty good (a little erratic and high, but it definitely starts right up). Plug in the ICV and it chokes and dies. So, I took one ICV and hooked up the plumbing to it, but disconnected the electrical connection. Then I plugged in the electrical connection to another ICV so that I could watch it as the car was running. It slammed itself completely closed when I started the engine. It's not supposed to do this, obviously, it's supposed to let air in at idle.

So, it's thinking that the car is not at idle. I checked the throttle position switch, both at the switch itself, and at the harness connector to the main Motronic brain. The open / close switch operates correctly, and the POT that changes resistance as the throttle opens registers the proper values. I also checked the two temp sensors that the manual suggested checking. Tomorrow, I will probably hook up the osciliscope feature of my multimeter to the unit and test the engine speed sensor. That is a likely culprit too, I suppose, since the car may think that the throttle is closed, but the engine speed is higher than idle.

Still no codes output by the computer, which is confusing to me. The car is running okay, but this idle problem is causing problems with stalling and rough running when cold and when coming off of full throttle. Despite searching, I have not been able to locate the O2 sensor. I don't have the car up on the lift, so it's difficult to see under there, but I still can't seem to locate it. I did locate what seems like an area where it should be (complete with bung), but there's nothing but a plug there. That I find odd - perhaps the conversion wasn't 100% completed. I'll have to call down to GIAC tomorrow and ask them if they have any more details.

There are some other details, I will post about them later on...

Old 11-27-2007, 07:31 PM
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