When hot it sputters & dies, wait, starts and runs great, repeat

ColoMustang21

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Hello, everyone. We have a 1994 GT 5.0 conv with only 83k orig miles, but it has a recurring issue that we, and several mechanics, have not been able to figure out.

The engine runs great, until it gets hot – then it starts to “sputter” and the engine dies abruptly. After it dies, the engine won’t restart. You have to let it rest 20-30 minutes or so. Then it will start right up, runs great like nothing ever happened for a few miles, and then the process starts again – sputters & dies, wait, starts and runs great, repeat.

We have thought it might be an ignition, fuel, or mass air flow sensor issue, and the following repairs have been performed, but still haven’t solved the problem:

Prior owner
Replaced O2 sensors
Replaced fuel filter
Replaced radiator, water pump
Replaced mass air flow sensor
Repaired air intake leak

Current owner
Cleaned mass air flow sensor multiple times
Replaced mass air flow sensor multiple times, with both aftermarket and Motorcraft part
Replaced ignition module (it is mounted in the heat sink on the fender, not on the distributor)
Replaced distributor
Replaced fuel filter

At last service at the shop, DLC scan shows no codes. A fuel pressure gauge was installed, car was driven for a few miles and fuel PSI stayed at spec.

Anyone have suggestions on what we should try next?
 
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joemomma

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My money is on something janky in the ignition, TFI or coil. Have you replaced the coil?

EDIT: on the TFI, I believe they have some thermal compound between it and the heatsink. Did you replace the thermal compound?
 

Rio red Cobra

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As colomustang21 stated just because the listed items were replaced doesn't mean the new one isn't faulty. Ive gotten several parts primarily electronic that were bad out of the box. Grap some electrical specs and get to know a multimeter inside out. Am 53 and just recently bought one. It took several days and a lot of questions until i understood how it works. I wouldn't be without one
anymore. Same goes for a PCV smoke tester.
 

PonyBoy94GT

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have you checked to make sure the injectors are getting their pulse when it wont start? stator switch inside distributor goes out a lot on these things and the injectors dont "fire" even though it will keep cranking when try to start it untill you kill the battery.
 

PonyBoy94GT

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also a trick to check is when it does it and its hot use a spray bottle of water and spray the hell out of the distributor, with the cap on, to cool it down fast. just the distributor! you dont need to be just aimlesly spraying water around on a hot engine! if it starts up after that its most likely the stator switch.
 

95 Blue GT

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Was the distributor you put on new or rebuilt. I replaced mine with a rebuilt one and it ended up doing the same thing so I went with a new MSD distributor.
 

dcm0123

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Power train control module also known as Constant Control Relay Module CCRM? $50 through RA but quality unknown

It is on the bracket which supports the radiator overflow tank. If you open yours up (easy to do) you will probably find burnt relays and components on the circuit board like I did. It controls fuel pump among other items.

When it will not start, can you hear the fuel pump running when you turn on the ignition swicth? It will only run for a couple of seconds unless you are cranking the engine or it is running.

You may also want to look at the connection on the fuel pump inertia switch located in the trunk.

 

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Adfalenski

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Why I previously said check fuel pressure is that once I had a fuel pump fail and only discovered it when I checked the pressure immediately after it died. The fuel pump was only pumping 5psi. I replaced the fuel pump and have never had the problem since. I also cut open the failed fuel pump and found the bearings were shot. When the fuel pump had cooled down enough the bearings had shrunk back enough to allow the pump to run for a little while until they began to seize again when they had heated enough because of friction.
 
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94SVTCobra

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Years ago I experienced a similar thing in my completely original and stock 1994 SVT 5.0L Cobra. The problem with mine was quickly discovered by a good ford tech following the book. It was the hall effect sensor in the distributor. The hall effect sensor is on the other end of the small wire harness that goes into the distributor. Just my experience. ...the hall effect sensor is aka "stator switch" among other things.
 

PistolGrip

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I'm following this with interest. I also have a '94 Cobra 5.0 5 speed with about 75,000 miles. I bought it about 20 trouble-free years ago. Mine has sounded/felt like it wanted to quit....cough...sputter - it felt like 3-4 spark plug wires came off as I was driving along under normal conditions - but has never actually quit. No dash lights have come on at all. After it sits for a while, it runs fine again for weeks. this has happened 2-3 times in the last 6 months. I have a friend who has a DBS 1 (or whatever that diagnostic tool is called). We're going to hook that up when he gets back in town. Hopefully it will tell us something. The uncertainty gets old quick!
 

95opal

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I'm following this with interest. I also have a '94 Cobra 5.0 5 speed with about 75,000 miles. I bought it about 20 trouble-free years ago. Mine has sounded/felt like it wanted to quit....cough...sputter - it felt like 3-4 spark plug wires came off as I was driving along under normal conditions - but has never actually quit. No dash lights have come on at all. After it sits for a while, it runs fine again for weeks. this has happened 2-3 times in the last 6 months. I have a friend who has a DBS 1 (or whatever that diagnostic tool is called). We're going to hook that up when he gets back in town. Hopefully it will tell us something. The uncertainty gets old quick!
If i had to guess in order
1 PIP n dizzy
2 TFI module
3 fuel pump
That being said ill take PIP for $1000 Alex
 

joemomma

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I'm following this with interest. I also have a '94 Cobra 5.0 5 speed with about 75,000 miles. I bought it about 20 trouble-free years ago. Mine has sounded/felt like it wanted to quit....cough...sputter - it felt like 3-4 spark plug wires came off as I was driving along under normal conditions - but has never actually quit. No dash lights have come on at all. After it sits for a while, it runs fine again for weeks. this has happened 2-3 times in the last 6 months. I have a friend who has a DBS 1 (or whatever that diagnostic tool is called). We're going to hook that up when he gets back in town. Hopefully it will tell us something. The uncertainty gets old quick!
You can get the OBD-I scan tool at AutoZone for like $30 if you don't want to wait on your buddy.
 

PistolGrip

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Full disclosure: I'm old and woefully computer/tech ignorant, so I need his tool to (hopefully) identify the problem AND his brain to interpret to me what I need to do. I can do without the car for a few days.
 

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