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Cold Starts problems?

Cold morning starts? I live in San Diego Ca. When the outside temperature is in 50 degrees range my 2003 Ford Ranger will not start and if it does start, once in gear half way down the block the truck cuts out completely. I wait a few minutes and do a restart and the truck starts up again usually does not cut out.
2003 Ford Ranger XL, 2WD, 5 speed, engine is 3.0L V6
Here is what I have done to the truck:

New Battery
New Starter (tested the starter no problems)
Crankshaft sensor
Fuel Pressure Regulator
Ignition start switch
The IAC and MAFS checked out fine.
The engine is getting fuel and spark checked out.

Ignition to engine failure when cold is the root cause. Thanks

There are four primary inputs into the computer when the engine is started cold.

These are the crankshaft position sensor, the throttle position sensor, the MAF/MAP sensor, and the coolant temp sensor for the computer.

The coolant temp sensor for the computer might be the problem.


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Thanks for your input. Can thecoolant temp sensor be tested? No code
light came on the dash board during these cold starts attempts. Thanks

It can be tested but why? Temp sensors are cheap. Swap it out in 10 minutes for $10 or $20. I think @Tester is right… swap and go.


Looking at the coolant temp sensor replacement on my 3.0 engine Ford
Ranger. I see that it is the one with just the one wire, not the
coolant temp sensor (PMC) with the 2 wires. Am I correct to replace the
one with just the one wire going to the sensor . Thanks

The coolant temp sensor with two wires is for the computer.


Got it …thanks again

My early 90’s Corolla has that symptom too. I know what is causing it, the idle air control is misbehaving. That part is difficult to source so I just live with it. Living in San Jose, except mid-winter it is seldom cold enough to cause any symptoms that warming up the engine in the driveway a few minutes doesn’t solve. But as part of diagnosing the problem I investigated the throttle position sensor, the computer’s coolant temp sensor, and I removed and cleaned the backside throttle body. So based on that experience, here’s what I’m thinking is happening in your case …

It’s possible to test the coolant temp sensor (the one used by the computer) if you can find a chart for its resistance vs temperature. Then all you have to do is measure the resistance and compare it against that chart… If you don’t know how to measure resistance, probably best to just replace it. Could work.

My guess however is something amiss with the throttle valve. So if the coolant sensor doesn’t pan out check the throttle position sensor, and after that, probably time to remove the throttle body and clean out the back side. It tends to get gunked up with pcv and egr gunk, and can make the throttle a little sticky, especially when it is cold.

If there’s anything tune-up related that’s due, I’d do that before anything above. For a 2003 – I’m assuming the engine is configured with COPs – so a tune-up would probably mean just new spark plugs, new engine air filter, check the idle rpm and base timing.