Electrical Dying Starter? Or Something Else?


New Member
Sep 4, 2009
Hey guys. Just last week, wednesday in fact, my stock 98 Mustang convertible started becoming slow to turn over. I've noticed lately that the longer she sits, the slower she fires up, but she does still reliably fire up. Now I have noticed that it's been hotter than normal lately and it started in the middle of our heat wave. Starts on average temp days (80f instead of 95-100f) do seem a second or two faster to fire up, but considering I'm not exactly being scientific about when I get behind the wheel, that may be placebo effect, considering I leave work at 11pm when it's cooled down to 80f and the starts are still

Some examples:
Sits overnight, turn the key for 5 seconds, starter turns but no ignition. Turn the key a second time, immediate ignition.

Sits for three hours between runs to the store? Almost immediate ignition. Definitely before the 5 seconds are up. Maybe 2-3 seconds.

Fire her up, shut her off, fire her up? Immediate turnover.

She's sitting on 128k miles, well maintained. In fact, I just finished checking and topping off fluids and replacing a faulty brake light bulb. I did remove the snorkel from the air filter as I've seen in a few recommendations. The problem began the day before I was fiddling about, so I'm somewhat certain I'm not to blame, but the snorkel is worth mentioning. I just replaced the original factory battery less than 1000 miles ago, so I know it's not that. But what about the alternator? A clogged fuel filter? A starter on its last legs? Spark plugs? Something tells me a lazy spark is the last option. But I did see someone say that fixed it for them on a "hot day" forum post I googled up somewhere.

Anyone got any ideas? I'd like to get back the faith that my pony'll still be starting next week, as she's my DD.

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After doing a bit more research, it seems the problem may be linked to fuel draining out of the carb overnight: She's not firing up right away because she's not still primed after sitting overnight. Any ideas on how to diagnose, confirm, and resolve that?
You might want to go back and do a little more searching. The Ford Mustang hasn't had a carb on it since 1985.

Your 3.8L V6 is fuel injected

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check your battery, check that the leads are connected tightly and don't move when you touch them, check the date on the side of battery when it was bought, it will be a round sticker with month and year made. finally test the battery with a meter to get an idea on how many volts its holding after being dormant, test this with the car off to get a true reading and not an alternator reading. Most likely from the way you've explained and I've understood it sounds like your battery is starting to diminish and not holding enough of a charge to keep it above 12 volts
I'll give the battery a check, but hopefully its not that as it is brand new as of about two-three months ago. I was having issues with the battery dying frequently, needing a jump almost every time I used the stereo or headlights for even five minutes with the engine off. Sounds like this could be a symptom of the same thing. If that's the case, prime suspect is the alternator, correct?
When you say

I've noticed lately that the longer she sits, the slower she fires up, but she does still reliably fire up.

Do you mean cranking speed is slower? Or that it takes more cranks over before it fires up?

When was last time you replaced fuel filter?
He may have but if he replaced with a battery with lower cold cranking amps or the same and he is pulling more electric than the battery will not be able to survive the amount needed to run his car. Think of it in term of fuel if u get regular compared to premium u get less octane and less power this works the same with cold amps the less u have the less u can do to the battery.

Jut for reference aesclepiuscrow what is the date, and cold cranking amps listed on ur battery?
Jut for reference aesclepiuscrow what is the date, and cold cranking amps listed on ur battery?

Had the local autozone test battery and alternator a few days ago both during a start and at 2,4k rpm, they said both were running as stock. I'll grab the date and cc amps as soon as I'm home and can pop the hood.

Do you mean cranking speed is slower? Or that it takes more cranks over before it fires up? When was last time you replaced fuel filter?

Problem has been more cranks before firing, from 1-2 cranks to 10-15. Up until last night fired up reliably after 10-15 cranks with a nice clean start. If you turn her off and crank her, she starts on the first crank unless she sits for a few hours then it goes back to 10-15. As of last night, she still fires after 10-15 cranks, but it's a very sloppy start, sputtering and almost dying before coming back and idling as normal. So I am suspecting a fuel issue now. Fuel filter hasn't been changed in about a year, so I am overdue. Was hoping to get it all at once with some new plugs and a tune up, kill the problem for good and get some of the old factory responsiveness back. I'll go swap it out and let you guys know how it goes.

Though, if there's no change, what's the likelihood of some faulty/clogged/stuck open fuel injectors?
Sounds like a fuel issue to me. If your plugs are old as well it could be a cause also.

Fuel injectors can sometimes leak inside the cylinder and cause starting issues as well. Basically the engine is flooded until it can clear with a few cycles.

Next time you let the engine sit for a while and you know it may have issues with starting, try starting the car with the accelerator pedal held to the floor. On a fuel injector car, this turns off the engine on a startup to help clear a flooded motor.

I honestly don't expect that to be your issues. 128k Is not a lot for injectors

When was the last time you replaced the spark plugs and wires?
Plugs were last changed about 50k miles ago, wires are factory wires. Gonna replace both of those along with a new coil pack here soon to get back the car's factory kick.

I did pick up a bit more info due to a tip from a friend the other day. He for a fuel issue, turn the key on and off a few times to prime the fuel pump. Sure enough, that has been shortening the number of cranks, to about 4-5 with a stable, firm start. I'm busy as hell at the moment so I'll replace the fuel filter hopefully this week during the holiday and then keep my fingers crossed my fuel pump isn't going out, but I'm guessing that fuel filter is killing the flow and the starts with it.
So filter is changed, the car seems to respond and idle better, but the starting issue remains. The sludge coming out of the old filter was a dirty, oily brown color so I'm guessing that may have fouled my plugs. I guess that's next. And if that doesn't help, I can only guess it means a new fuel pump. Meh.
So the starting issue has improved, but seems a little less predictable. Still reliable though, once she turns, she runs like a champ all day. Yesterday before work she fired up right away. Leaving work, cranked like she has during this whole issue. So I'm grabbing the fuel cleaner here in a bit to see if that doesn't kick it out for good.

But I've noticed something else that may be a symptom of the overall problem. When she starts, she idles higher than she did before. Fires up and holds at 1k rpm before dropping down to 800pm after about 5 seconds. Before, she'd fire up and drop to 800 rpm at idle almost immediately. If I give it a little gas, the rpms hang before coming down instead of immediate drop. So for instance, before: gas, rpms rise and fall in a steady motion. Now: gas, rpms rise, linger 1-2 seconds, then fall. Is that indicative of the possibility the injectors are momentarily sticking open before closing?
Okay, popped some seafoam in there and ran her around the city for a while. If there's any changes, I'll post success/failures.

Another new issue I've been seeing is more 'aggressive' starts. With foot completely off the accelerator, the car now starts as though gas is given, rushing somewhere near 2k rpm before settling to 1k, then down to 800 idle. Now, I assume this is cause the filter is no longer retarding the flow, but the revs on start are not clean or stable, more like its burning a burst of fuel it just suddenly found hanging out in the cylinder.

In the meantime, I'm going to clean the maf sensor and examine my o2 sensors just in case there's a sensor/mixture error, so I'll post an update on that as well when its done.

By the way, folks, I greatly appreciate the help.
have to see a video, but that might be normal. Most every car I've owned revs high upon startup and then settles down to idle. Cold starts are usually done rich, and that is the result

I'm not sure i'd read into that too much. What you had before might have been the abnormal situation.

Def sounds as if you were starving for fuel. It might take some time for the car to adapt to the amount of available fuel and adjust the injector pulse width, so perhaps the high idle starts might ease back. With the fuel filter clogged, the injector pulse width was probably increased to compensate and try and add more fuel.

If you don't mind reprogramming your radio again, i might suggest unhooking the battery and resetting the ECU and forcing it to relearn idle strategy. Might make the relearning process quicker.
I have read the it is pretty common for the synchronizer to fail after 120K miles. The synchronizer times the injectors, and it seems that you might have a fuel issue...