1986 Ranger runs rough cold

[Alaska Diesel]

Ok that's what I guessed. I've changed that sensor.

 

[Alaska Diesel]

Does anyone know what the timing advancement range is?

 

[Nez'sRanger]

Yeah, it's supposed to be 10° btdc with the spout connector unplugged.

 

[Alaska Diesel]

When it is running and you step on the throttle what range should the timing advancement cause? With the spout connector in?

 

[Nez'sRanger]

Hmmm. Not entirely sure... I know at idle it is pretty high with spout in... Like mid 20's, maybe even 30 (it's been a while since I've done it on mine), but I couldn't give a definite range. Hopefully someone else can chime in for you?

 

[Alaska Diesel]

Mine is idling at 35 degrees roughly. But if I add throttle it will jump to around 0 degrees and then if I hold it there, it will backfire, sputter, and die. What is this suggesting?

 

[Alaska Diesel]

So I think I've found a lead here. When I unplug the vacuum from my MAP it runs perfectly good. When I plug it in it runs to lean. I put a vacuum pump on the MAP and it runs good with no vacuum pressure but runs like it does hooked up to the engine vacuum when there is vacuum pressure. The vacuum pressure of the intake manifold is 300 mmHg. idling and drops to zero when I add throttle.

 

[Alaska Diesel]

I have 5 volts coming to the MAP sensor plug and a good ground coming to it. I also have .5 ohms of resistance going from the MAP to the computer. I think my MAP is bad. I'm ordering a new one and we'll go from there.

 

[PetroleumJunkie412]

Damn fine troubleshooting work if it is.

 

[Nez'sRanger]

You might be on to something... Just checked my engine emissions diagnostic manual, and it says the voltage should be around 1.56 +/- .04 at 1000ft. I'm curious to see how it runs with a new one!

 

[Alaska Diesel]

You might be on to something... Just checked my engine emissions diagnostic manual, and it says the voltage should be around 1.56 +/- .04 at 1000ft. I'm curious to see how it runs with a new one!

Is that on the computer side of the MAP sensor?

 

[Nez'sRanger]

Yeah

 

[Locotomb]

The spout plugged in, timing is controlled by the computer once warm and can't be adjusted. Other than the initial 10deg tdc. Just throwing that out there for posterity.

 

[Nez'sRanger]

Is that on the computer side of the MAP sensor?

Computer side... You do mean the return side, right? In that case, yes.

 

[Alaska Diesel]

Yes I do mean the return side.
Put the new MAP sensor on and still runs just as bad. Going to start checking my other sensors

The spout plugged in, timing is controlled by the computer once warm and can't be adjusted. Other than the initial 10deg tdc. Just throwing that out there for posterity.

What could cause trouble with that? I've been wondering about that.