1986 Ranger runs rough cold


Alaska Diesel

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I have a 1986 Ranger 2.9l 4x4 manual. It will run way too rich especially when cold. I have to really play with the throttle to rev it up and even to keep it running. I'm pretty sure my vacuum is good. And I changed my ECT temperature and swapped my IAT out. Still is hard almost impossible to keep run when cold. Has a smell of gas in the intake. I've also put a different map sensor on, tried a different computer. If I unplug the ECT or IAT sensors it will run good. I'm stumped on this little guy.
Fuel pressure is good.
Once it warms up it's a lot better but it still has a hesitation and acts like it's flooded
O2 sensor is new a couple years ago. I've only put 80 miles on it since then because the fuel pumps went out and after the fuel pumps went out I've had this issue.
 


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rusty ol ranger

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Check the FPR vacuum hose for fuel
 

bobbywalter

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sounds like classic fpr.


or shitty pluggy injectornators.
 

Alaska Diesel

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What is the fpr?
 

alwaysFlOoReD

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Fuel Pressure Regulator
 

Alaska Diesel

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Fuel pressure regulator is working good. Not sure if the vacuum line smells like fuel, but the fuel pressure on the rail is what it is supposed to be.
 

Alaska Diesel

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Paulos, how would I check the air bypass valve? It is a couple years old and only has that 80 miles on it.
 

Rusty Bouquet

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Have you tested the tps (throttle position sensor)?
 

Locotomb

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Sounds like the Air By-pass valve (IAC) isn't opening. Maybe this has something to do with it, or it's just bad.
I agree, Except some of the new IAC don't have a D on the connector. Specially if its not FoCo. So beware it can still have a diode inside.
 

rusty ol ranger

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Fuel pressure regulator is working good. Not sure if the vacuum line smells like fuel, but the fuel pressure on the rail is what it is supposed to be.
They can still fail and hold pressure. The fuel leaks past the diapragm and straight through the vacuum hose into the motor, making it pig rich.
 

Paulos

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Paulos, how would I check the air bypass valve? It is a couple years old and only has that 80 miles on it.
When the engine is cold the IAC should be open. When you start it up cold, pull the connector off the IAC. It's basically a solenoid that engages when cold, and allows fresh air to by-pass the throttle body (which would be closed). If you don't hear the solenoid disengaging and engaging when you disconnect/connect the connector (engine cold) there's an issue with it. Check the pdf file I attached earlier and see if you got a later model IAC. If so, according to the pdf, swapping the two wires should fix it.

You could also connect 12 volts to the IAC to test the solenoid. If it doesn't work, switch the wires and try again. If it doesn't engage with the polarity either way, it's bad. With 80 miles on it, it can't be clogged up.
 

Alaska Diesel

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Yes I've tested the TPS, it's good.
I'll test the IAC as soon as I can.
Paulos the pdf you attached doesn't come up with anything.
 

Nez'sRanger

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Yes I've tested the TPS, it's good.
I'll test the IAC as soon as I can.
Paulos the pdf you attached doesn't come up with anything.
It may be the browser you're using. I had the same problem. I tried it with Google chrome, and it worked.
 


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