Mechanics

CAR WON'T START WHEN IT'S COLD

1999 Mercury Mystique

Engine problem
1999 Mercury Mystique Two Wheel Drive Automatic 140000 miles

The car won't start when it's cold. The starter cranks, the engine tries to fire but doesn't catch. If I put the car in the garage to warm up, it starts and runs well. I've added dry gas, replaced the fuel filter, changed the ignition coil, wires, plugs and oxygen sensor. I'm at a loss.
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Sideslip1960
February 4, 2008.



Sounds to me like you need a new coolant temperature sensor. #1 cause of a cold start problem.

Blackop555
Feb 4, 2008.
Are you sure you changed the engine/coolant temperature sensor? If you unplug the connector the temp guage on the instrument panel should stay the same, not peg all the way hot or cold.

Do you have a cold start injector? It looks like a fuel injector but not exact. There is one. Installed on your vehicle.

At the time it wont start check for spark and fuel pressure at your fuel rail.

Blackop555
Feb 13, 2008.
I changed both the coolant temp. Sensor and the engine coolant temp. Sensor. Also, the spark and fuel pressure have been check. The reason I changed the ignition coil is that I thought maybe the spark just wasn't strong enough when cold. Not the problem.

I will check the cold start injector.

Tiny
Sideslip1960
Feb 13, 2008.
Will it start if you have your foot on the throttle about 1/4 while cranking?

Has the fuel pressure been checked on cold mornings at the fuel rail, right away? Not after its been run but right when the problem is occuring?

Also check for vaccum leaks on all hoses and around the Intake manifold when you get the vehicle running if its warm, spray a can of carb cleaner on the vaccum lines and base of the manifold, if idle changes you have found a leak.
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Blackop555
Feb 13, 2008.

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