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'86 2.9l v6 won't stay running after about 10-15 minutes


ezmoney2884

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Vehicle Year
1986
Make / Model
Ford
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Automatic
I have an 86 Bronco II 2.9l V6. It cranks great and runs smooth for about ten or fifteen minutes and then it starts to sputter. this can last from 30 seconds to a minute and a half and then it dies. It will not crank right back up. After it sits for fifteen to twenty minutes it cranks fine and runs smooth until the engine starts to heat back up. The process repeats from there.

The longer it sits between cranks, the longer it runs but never longer than fifteen minutes, roughly.

I just replace the inline fuel pump and filter.

Any other suggestions on where to look next?

Also, It idles at about 1500 RPMs in park and 1000 RPMs in gear. Not sure if that is normal.
 


RonD

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Welcome to TRS :)

Reads like classic TFI module issue.

Good read here on TFI testing: http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

The TFI module on the distributor warms up and then stops working.
One person on here used a bag of ice to test that, lol.
After engine quit he put bag of ice on TFI module for a couple of minutes and engine restarted faster.
Got new module and all was well.

Also the Coil can have the same symptom, warms up then stops working.


When cold those idles would be OK
After engine warms up then, if you have an automatic trans, you should be 750-800 in Park and 850-900 in gear, manual trans would be 100 less in neutral, no in gear change.

On fuel injected engines Idle is set by the computer using the IAC(idle air control) Valve.
Upper intake on throttle body, looks like a can/tube mounted sideways.
Computer adjusts the valve to let in more or less air which raises or lowers idle RPMs, like a controlled vacuum leak.
These can be cleaned.
Google: ford ranger IAC Valve clean

BUT...........you may have a vacuum leak, after engine is warmed up, assuming you fix the 15 minute run time :), unplug the wires from the IAC Valve, it will close all the way and engine RPMs should drop to 500 or engine may even stall, either is good because it means no vacuum leaks.
If idle stays above 700 then you have a vacuum leak, or someone has messed with throttle linkage screw
 
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