1986 Ranger runs rough cold

[Nez'sRanger]

I think the ECU gets the rpm from the tfi module via the hall effect sensor inside the distributor. I could be wrong...

 

[alwaysFlOoReD]

Ah, I didn't look at the title when I answered. I was thinking edis and 4.0.

 

[PetroleumJunkie412]

Ah, I didn't look at the title when I answered. I was thinking edis and 4.0.

...no words man. No words.

 

[Alaska Diesel]

Would there be a way to test that hall sensor?

 

[PetroleumJunkie412]

Would there be a way to test that hall sensor?

Yup. Timing light and watch advance at idle with connector out and in. If it walks around with the spout connector removed, likely hall effect sensor went bad. Should hold time nearly perfectly. When I replaced mine, I could set timing to.fractional degrees if I wanted to.

 

[Alaska Diesel]

Ok I'll try that.

 

[Alaska Diesel]

How would I test the O2 sensor?

 

[Alaska Diesel]

Yup. Timing light and watch advance at idle with connector out and in. If it walks around with the spout connector removed, likely hall effect sensor went bad. Should hold time nearly perfectly. When I replaced mine, I could set timing to.fractional degrees if I wanted to.

I checked it like you said. With the connector out it stays in one spot. With the connector in it will move one way if I slowly add the throttle but if I quickly add throttle it will move the opposite way as before and that's when it really runs rough and will almost die until it moves back to where it was before. Hope this makes sense.
Any ideas of what to check next?

 

[Alaska Diesel]

How would I test the O2 sensor?
Edit I read that the truck doesn't use the O2 until warmed up.

 

[Alaska Diesel]

What should I check next? There is no black exhaust.

 

[rusty ol ranger]

I really think you got an ECM issue

 

[Shran]

I believe you can test O2 sensors by heating them with a propane torch and watching resistance numbers on your meter while the sensor warms up. I do not know what those numbers should be though.

Interesting that your timing retards like that. I'm not sure if it's supposed to do that or not, I should throw a light on mine and see what it does.

 

[Alaska Diesel]

I'll put the other computer on it again when I have a chance.
Shran, that would help if you could throw a timing light on yours to compare it to.

 

[Alaska Diesel]

Correct me if I'm wrong, the engine does not run off of the O2 sensor until past a certain temperature. So if I'm not getting the right temperature reading it could be throwing the computer off. In that case which sensor matters, the ECT or the temp gauge? My temp gauge does not work.

 

[alwaysFlOoReD]

The ect feeds temp info to the computer. It is a 2 wire sensor.