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94' Ranger Idle Stalls When Hot


94' Ranger

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Southern California
Vehicle Year
1994
Make / Model
Ford Ranger
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Manual
My stickshift 3.0 1994 Ranger started giving me issues the other day. I drove for about half an hour, parked it, and it wouldn't start back up till it cooled down. On the drive home I had to give her gas when idling to keep it from stalling. My first thought was a bad vacuum leak so I thoroughly inspected my vacuum lines and went through two bottles of carb cleaner spraying all over looking for a leak, no luck. I inspected my EGR and PCV valves but didn't see anything obvious. It sounds to me like a fuel/oxygen ratio issue but I'm not sure where to start looking for the problem.
It will start right up with no issues until it gets fairly hot, I can drive for maybe 15 minutes without any problems. After being warmed up and parked, it will start then idle for 10-40 seconds before the idle gets really rough and the truck will stall. There are no audible or visual changes that happen when it starts to stall out, the idle just get real rough then slows to a stall. Within the last year, I've replaced most of my ignition system including the ignition coil, all spark plugs + wires, and my distributor.
Today I am going to try to use OBD1 to see if it'll tell me anything but I thought I'd ask here to see if anyone might be able to point out any likely culprits or just give me a few ideas of where to look/test next. Thanks in advance for your help!
 


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ericbphoto

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In theory, theory and practice are the same. In practice, they are different.
Might want to check the engine coolant temperature sensor. This is the 2-wire device that sends info to the ecm. Not the 1-wire device that runs the gauge on the instrument panel.
 

RonD

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Welcome to TRS :)

1994 3.0l will use a remote mounted TFI module for spark
A common complaint with distributor mounted TFI modules was that they would get heat sensitive and engine could run rough or stall after warm up and then not restart until TFI module had cooled off

Your TFI module should be mounted on the Rad support, engine side, usually on drivers side

When you are moving there is more air circulation in engine bay when stopped(idling) the engine bay will heat up a bit, and when engine is off engine bay will heat up a lot, no fan, so TFI would also heat up in both scenarios
But just a guess

Remote mounted TFIs look like this: https://www.supermotors.net/getfile/835324/fullsize/ignition-mudual.jpg

Big heat sink with fins, the plastic TFI module in the center
Locate it

Then try this
Carry a bottle of water, and maybe a hose so you can pour the water onto the TFI module when you have a crank but no start
See if cooling off the TFI module works to get engine to start
If so replace module
If not move on to something else

Also look at the CEL(check engine light)
It should come on with key on
And then go OFF while cranking engine over,
It goes off when computer SEES a TDC timing pulse from the TFI module
If there is no timing pulse then no fuel injectors will open


Air/fuel mix seems like a longshot for the symptoms, usually you would notice this at highway speeds
 


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