1995 GT- Engine Hard to Start

1995 Mustang GT (5.0), 127,000 miles

This morning I went out to start my car, and the engine turned, but failed to start.
The snow is melting, so while it's not too cold, there is plenty of humidity.
After a few tries (where it never seemed to fire at all), it finally did so, and I was able to get it stared. Once running, it gave an occasional *cough* out the exhaust. (This seemed to disappear later down the road.)
I drove it around, without further problems. It also started fine on my way back home.

I have very limited service records on this car (I have had it for the last 5,000 miles, since august '09), and am considering giving her a tune-up.

Is there a way to test the ign coil?

...while it's not too cold, there is plenty of humidity...

I think you're answering your own question. Sounds like you're getting some misfire when damp. I would go with plugs & wires as the first step.

The coil wire is a sore spot for arching issues, make sure it's routed away from anything. If you look closely at the old wires you may actually see burn / carbon marks where the spark was jumping off.

Look at the body of the coil (plastic) where it sits inside the metal frame. Sometimes you can see the same burn marks on it. "Blue Streak - Standard" makes a better quality "X" series. It's baby blue in color and way better than some of the "performance" crap out there.

Thanks for the info. It hasn't acted up since that day, so the humidity may have been the issue.

Now I'm even more certain it was the humidity.
This morning the same thing happened. Lots of melting snow all over the place, and it fired up right before I was just about to give up on it. Seriously, I was [this] close.

I'm definitely going to give her a tune-up before long.
Any other parts reccomendations?

I'd look into either a fuel delivery or spark delivery issue. If you have the tools check the fuel rail pressure and if you did not have the fuel filter replaced within the last 20,000 miles, replace it. Since you have limited service records, just take preventative maintenance and replace all fluids, filters, plugs, and plug wires to prevent issues later.

You can do all of the above tune up items yourself with minimal tools - just some screw drivers and socket wrenches. The only one that may be tricky is power steering reservoir. I got creative and use a turkey baster for that one.

If there's visible moisture on your car, meaning the humidity is condensing over night at the lower temps, it's possible that moisture has gotten into electronics that has a bad seal. PCMs sometimes have these problems. You can pick up a PCM from a junkyard or online on the cheap so don't fret too much. It MUST match the same code as your current PCM, though.

If it happens again, after trying for a little bit, pull out the tools and pull a spark plug out. If there's fuel on it, it's a spark issue. If it's dry, it's a fuel issue.

I apologize, I forgot to mention I smelled gas after cranking it for a while (before it started).

Lucky for me, the previous owner seems to have parked it where it got plenty of sun. I was just barely able to make out the shadow of the dealerships name where the badge was removed.
I had them run the VIN for service records, and found a "Fuel Induction System Cleaning" was performed at 105,000 miles. That wouldn't include the filter, would it?

I found out the coil can be checked by resistance. I've come across some specs, and will check it later today; I'll post my findings then. (still not ruling out that tune-up... that's getting done even if it's not causing the problem)

Ok, here's what I got for the coil:

The primary gave a reading of 0.2-0.3 ohms
The secondary was 7.7 k-ohms, which changed to 9.2 k-ohms after about half an hour of driving.
The primary-to-case was open, no connection.

The spec-sheet I have calls for 0.8-1.6 ohms on the primary, 7.7-10.5 k-ohms on the secondary, and a primary-to-case of 10 m-ohms.

So it is technically out-of-spec, but I'm seeing these values advertised on new coils, too. For example, a new Accel 140012 has a primary resistance of 0.2 ohms, the same value I'm getting now.

Since you smell gas I'd definitely look for a spark issue. Check the timing on the distributor, too. If it's been too far advanced by the previous owner, it can be hard to start.