wont start when hot

25

Asked by Nov 27, 2007 at 08:57 AM about the 1993 Ford Mustang

Question type: Maintenance & Repair

car tends to cut out when it gets hot, often stranding me till it cools down

16 Answers

205

I'm not a car expert,but from experience,the first thing to change when a vehicle over heats is the thermostat."Thermostat-a few bucks.Not being stranded-Priceless"

2 out of 2 people think this is helpful.

you could have a bad coil pack.

4 out of 4 people think this is helpful.
40,295

It wouldn't surprise me if the fuel pump was going out on you. I've seen vehicles that would shut off when the temp got above a certain point and it was the fuel pump. However, it could be a bad ignition module also, these need to be tested dynamically, meaning they are put on a machine that warms them to operating temperature and then runs the tests. Advance Auto Parts can do this for free.

1 out of 1 people think this is helpful.
1,165

I can think of 2 possibilities. 1- if it cuts out when hot ,like it is running out of gas , you might have a fuel pump , or fuel pump relay on the way out. 2- if it cuts out like you turned off the ignition , you could have an ignition module on the way out , or possibly a cam/crank sensor on the way out . If you have been getting a "check engine" light coming on ( amber light )it might have set a code and you can trace the problem from whatever the code flags .

1 out of 1 people think this is helpful.
55

i had that same problem one time, i have a 91 5.0L and it was my fuel pump....

2 out of 2 people think this is helpful.
835

if the car will start normal when its cold something is bad ignition related coils, wires, spark plugs. if it won't even crank over the starter is too hot and probably has a heat shield missing from between it and the exhaust manifold or headers. is it a 5.0L H.O. ? as it will have headers stock and the heat shield could have rotted away.

1 out of 1 people think this is helpful.
75

mine did that for a while but i adjusted my timing and it stopped

2 out of 2 people think this is helpful.
210

I agree with a few here, it's most likely an ignition problem. Ford's EEC ignition modules are known to have this exact problem. Ignition coils are universally known for it, too. It's fine when it's cold, but after they heat up the plastic exterior expands and if there are any cracks, they will open up and short it out. After it cools, the cracks close up and it'll be fine until it heats up again. Distributor cap, rotor, and wires can all cause the same issue. If they haven't been changed in awhile, do a tune-up and see where it gets you. If you want to really figure it out, do the tune-up one piece at a time to weed-out the problem. Change the wires, drive it, change the cap & rotor, drive it, change the coil, drive it, change the module, drive it. It could also be the fuel pump, but they're usually a bit more random than that. The fuel pump is naturally cooled by being submersed in the gas tank. If this commonly happens when there is very little gas in the tank then it likely could be that. If it always happens when the engine gets hot no matter how much gas is in the tank, then it's more likely to be ignition. A fuel pump submerged in gasoline is certainly not getting hot, so it's not as likely to be a problem consistently when the engine heats up. It would be more random, and would likely cause intermittent starting problems, hot or cold. Another possibility is oxygen sensors. These poor OBD-I computers in these cars are not very reliable for reporting problems. I had problems for nearly a year that no one could figure out. It would start fine, idle fine for a few minutes, then the idle would drop out and save itself a few times. If you took off driving right away, it'd be fine at first. Then, when the engine warmed up, it would sputter, run lousy, and smell like it was rich at part throttle cruising, but ran like a champ if you put the pedal to the floor. It would do this for about 5 miles or so, then it would just suddenly clear up and wouldn't do it again all day. Next day, same cycle again. There was no check engine light, and I checked anyways many times, but there were no codes, either. Nothing showed on any shops scan tools, and we tweaked and tuned and replaced just about everything. Then on a suggestion from an old expert (you know, the guy who just looks at the car and tells you what is wrong with it), I replaced the O2 sensors. That was it, never had the problem again. The computer should have told us that was the problem, but it didn't. Listen to the car and it'll tell you what is wrong. As meanoldmoe mentioned, you should be able to get closer by watching when and how it happens. If the engine just straight cuts out, then it's probably ignition; no ignition, no spark, no combustion. If the engine stalls, then it would steer you more towards fuel problems; no gas means running on fumes, less combustible, but will sputter until gone. With the O2 sensors, it only stalled at idle. It ran like crap when driving, but it kept running. When it cleared up, that was the computer going into "limp-home" mode where it ignored the O2 sensors and ran on a pre-programmed fuel map instead of adjusting on the fly according to sensor input.

8 out of 8 people think this is helpful.
35

Vaporlock is the first thing that came to my mind but I have no clue how common it would be in more modern cars...Im only familiar with 68s...

1 out of 1 people think this is helpful.
6,675

sounds like an ignition problem. could be a good opporunity for you to put a high performance ignition system in if you were ever looking to do upgrades on your car.

1 out of 1 people think this is helpful.
2,375

Sounds like an overheating ICM to me. Ignition Control Module. Assuming you have the 5-liter, it's the sensor bolted to the side of the distributor...it's rectangular. Certain Fords have problems with them while others don't, it's really a hit or miss deal, but what will happen is the ICM will overheat and when it does, it will fail to trigger the ignition coil so you'll lose spark until the module cools back down. If the problem is in the module (they're not difficult to replace but you will need tamper-proof Torx bits), you just need to replace the module with a *decent* quality brand ICM and then clean the flat plate on the distributor that it bolts to, and apply a good coat of di-electric grease (should be included with the ICM) before you install it. The back of the ICM is the heat-sink and it needs to transfer heat into the distributor to avoid overheating....so if this surface is not clean or you don't use the included grease, the module will overheat and fail. I don't have anything like AllData at my disposal to tell you how to test the module with a DVM though...

5 out of 5 people think this is helpful.
345

Being in the buisness the first thing I thought of was vapor lock , try to find a new venilated gas cap ..

1 out of 1 people think this is helpful.
10

My 2006 ford mustang gt shuts off and idle down. Tried changing battery/alternator/throttle body position sensor/cam a&b alignment sensors and cleaned throttle body. Nothing has helped. Please help.

1 out of 1 people think this is helpful.

most likely fix would be a TFI module and stator(.pick up in distributor ) and module attached to dist,hope this helps

1 out of 1 people think this is helpful.
20

Have similar issue. Car was running fine I turned it off and the restarted it and it wanted to shut off so I gave it gas and it stayed on. Another day went by turned car on and it started and then turned off. Tried it everyday and sometimes would start then sometimes wouldn't. But if it did car would shut of . Replaced the fuel pump and still same thing. Replaced coil and still doing same thing. Anyone have any other suggestions?.

2 out of 2 people think this is helpful.

Thanks for all the helpful tips. I wish it was as simple as cutting off after driving or not restarting. But it will just not crank after sitting overnight. This vehicle is brand new - and the dealer has no clue how to address the problem. Again thanks for all the responses.

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