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1993 Subary Legacy- Battery tests okay, but slow start at lower temperatures

My Subaru wagon is so temperature sensitive that I could probably use it as a thermometer. At 80 degrees F, or so, it starts with very little hesitation. Any lower than that, and it takes a while to turn over, and there are clunking sounds. Lower temperatures mean increased clunking and a longer start time. I’ve always managed to get it going so far, and I live in a place that’s very hot in the summer months, so I’m fine for now, but come September, I’ve got a problem.

I’ve had it looked at by two local mechanics and they confess to being stumped- battery tests fine, starter seems good, fuel additive didn’t make any difference- anyone have any other suggestions?

Are you testing the battery cold, or after it has had a charge from driving it to the shop? If this battery is more than 4 years old, go ahead and change it before the weather turns cold. A winter’s cold will make a weak battery fail.

Have a Subaru specialist put a scanner on it and read the injector pulse width when cold cranking. It should probably be around 20-30 msec, but the specialist should be able to find the exact spec. The pulse width is probably too short, meaning not enough fuel is being injected during cold start.

When they find pulse width is too short, then check the coolant temp sensor output. If the sensor output is bad, it could be the reason for the too short injector pulse.

Also have the camshaft and crankshaft sensors checked. Apparently 1990’s Legacies have a problem with these. They can be intermittent when cold, causing hard starting, but then work fine when they warm up.

Also, clean battery terminals and grounds to chassis and engine. Make sure all the starter connections are clean. When it’s cold does it turn over slower?