Stalling when at peak operating temp

CJ-

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Hey guys, the problem I’m having is that once I’ve been driving for about 45 minutes, my car will stall and take about a minute to start back up.

The stall is sudden with no hesitation or lumpy idle before, just off suddenly like the key was turned off.

I datalogged and got lucky and a stall occurred while logging and I noticed the FPF (fuel pump output fault detected) triggered a Yes 3 seconds before the stall occurred. So I check my fuel relay under the hood and that sucker is hot as hell.. I swapped the relay for another and it’s not stalling but I’m afraid it’s a matter of time before the other relay gets too how and stalling happens again. I read that this could be a sign of a bad fuel pump, any advice out there?
 

07 Boss

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Could be. You should check FP duty cycle compared to rail pressure and see if they coincide with each other. Another thought is that some of the early S197's had an issue after a long steady run with little throttle input, like cruising down the freeway, that something to do with the pump causes some time of cavitation and it doesn't push fuel through. Maybe pull the pump and see what the sock on the bottom looks like. I know another guy who was having the mentioned issue and I sent him my old fuel pump (2007) and it fixed his issue. I think there may be a TSB on it for the 05-06 cars, memory is a little foggy at my age.
 

CJ-

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Could be. You should check FP duty cycle compared to rail pressure and see if they coincide with each other. Another thought is that some of the early S197's had an issue after a long steady run with little throttle input, like cruising down the freeway, that something to do with the pump causes some time of cavitation and it doesn't push fuel through. Maybe pull the pump and see what the sock on the bottom looks like. I know another guy who was having the mentioned issue and I sent him my old fuel pump (2007) and it fixed his issue. I think there may be a TSB on it for the 05-06 cars, memory is a little foggy at my age.

I’ll definitely do that tonite!
In the meantime I have a bit of an update, lastnite before heading to bed, I swapped the fuel pump relay with another and this morning I babied the car to work so I’m not forcing the fuel pump to work hard and didn’t use the AC at all. The car didn’t stall once... tonite when I get out of work, it’ll be about 11pm so the freeways will be empty so when I get close to home I’ll try some hard pulls with ac turned on and try to stall it... it is stalls then I guess the relay swap helped.
 

CJ-

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Could be. You should check FP duty cycle compared to rail pressure and see if they coincide with each other. Another thought is that some of the early S197's had an issue after a long steady run with little throttle input, like cruising down the freeway, that something to do with the pump causes some time of cavitation and it doesn't push fuel through. Maybe pull the pump and see what the sock on the bottom looks like. I know another guy who was having the mentioned issue and I sent him my old fuel pump (2007) and it fixed his issue. I think there may be a TSB on it for the 05-06 cars, memory is a little foggy at my age.

Ok this is what I got but I’m confused because my FP Duty cycle, Fuel rail sense read as different units of measurement.
FP Duty Cycle reads as Percent and the rail sense reads PSIand the rail pressure sense V reads Voltage.

Here’s a video of the readings I got... don’t lol at my dinosaur tuner please.

https://youtu.be/qQ5qlCfw390
 

CJ-

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Btw on my way home, I waited till I was close to home (35 minute drive) and I floored it a few times all the way to 6k rpm and got no stall... maybe the relay swap helped some... or maybe cause tonight was a lot cooler than yesterday and played a factor.
 

JeremyH

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If your lucky could just be the relay, but also when relays get hot its usually from the load (fuel pump) drawing too much current. Can be caused by a really clogged fuel filter or a failing pump. There is a tsb for an issue with hot stall/sputter for the 05/06 pumps. I would replace the fuel filter if it hasn't been done and think about replacing the pump. It is a wear item and flow goes down over time as the brushes and commutator in the fuel pump motor wear. If its not flowing right it could be getting driven harder to maintain pressure. The fpdm has thermal shutdown protection as well so if the pump draws too much current it will trip and cut power to the pump. Inspect the wiring and fuel pump fuse as well for signs of heat. If you want a pump I have lots of stock ones from the hats I upgrade. I throw out all the 05-06 pumps because of the tsb but keep the 07-10 pumps. Cover shipping and you can have one.
 

CJ-

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If your lucky could just be the relay, but also when relays get hot its usually from the load (fuel pump) drawing too much current. Can be caused by a really clogged fuel filter or a failing pump. There is a tsb for an issue with hot stall/sputter for the 05/06 pumps. I would replace the fuel filter if it hasn't been done and think about replacing the pump. It is a wear item and flow goes down over time as the brushes and commutator in the fuel pump motor wear. If its not flowing right it could be getting driven harder to maintain pressure. The fpdm has thermal shutdown protection as well so if the pump draws too much current it will trip and cut power to the pump. Inspect the wiring and fuel pump fuse as well for signs of heat. If you want a pump I have lots of stock ones from the hats I upgrade. I throw out all the 05-06 pumps because of the tsb but keep the 07-10 pumps. Cover shipping and you can have one.

I will gladly accept your offer, thank you very much! I’ll pm you shortly.
 

CJ-

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Update, the success of the relay swap was short lived. It stalled again on my way to work this morning. So JeremyH... I would 100% appreciate getting a second hand fuel pump from you.
 

boomer9999

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I'm curious when it stalls, do the dash lights, radio, etc. still stay on?

This can narrow it down to a bit.

I do know on other vehicles that a faulty crankshaft position sensor will cause a stall. Also a failing MAF can cause a stall.

I'm just trying to think of the components that would be heat sensitive and cause a complete engine shutdown without effecting anything else.

Oh and I wonder what would happen if the ignition key chip reader was flaky. Will the engine shut down if the key reader has decided it doesn't match with the key?
 
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CJ-

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I'm curious when it stalls, do the dash lights, radio, etc. still stay on?

This can narrow it down to a bit.

I do know on other vehicles that a faulty crankshaft position sensor will cause a stall. Also a failing MAF can cause a stall.

I'm just trying to think of the components that would be heat sensitive and cause a complete engine shutdown without effecting anything else.

Oh and I wonder what would happen if the ignition key chip reader was flaky. Will the engine shut down if the key reader has decided it doesn't match with the key?

Everything stays operational, engine cranks but absolutely no hit of it trying to start unless I wait a minute. I ran my live data just a minute ago and 2 things I’m curious about, the baro pressure sensor and one of 2 ECT reading i have. As far as baro... I don’t know if it’s in range for Los Angeles California. And the ect, I have no idea but in the picture I have 2 ECT readings and one is correct and the other is at 90F degrees???
 

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CJ-

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Well I think I found the culprit, I had failed to mention that everytime my car would randomly stall, I would get the same pcodes: p0010 p0020, 2 evap codes, readiness code, o2 sensors and p689. So I googled it yesterday and found a hit but not in a mustang forum... but in a f150 forum, well they experience the same issue except with one difference, they find a blown #32 fuse which ties all those sensors together. The reason that fuse blows is usually an o2 sensor wire melting against the exhaust manifold.... well went through my fuses and diagrams, and since my mustang doesn’t share the same fuse box as an f150, I do not have a fused link that all those components share... so what happens then, we’ll instead of a fuse blowing, I get a short and my ecm or pcm cuts ignition power to the engine for about a minute before it allows it to start up again.

So I looked under the hood at the drivers side o2 sensor and I could see the wire was awfully close to the exhaust manifold flange, so I reach down and pull it up and notice the sweet smell of burn wire insulation and also notice the plastic retainers that hold the o2 connector to the head wasn’t attached so I hang the wire on a clip that retains some
Ac line against the firewall. Happy to report this morning no stalling, I’ll report back any changes if it stalls again.


Cliff notes,

Stall with pcodes:
P0010
P0020
P0443
P0446
P0689
P1000


Equals melting o2 sensor wire on exhaust, causing short. (In my particular case)
 

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07 Boss

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Well I think I found the culprit, I had failed to mention that everytime my car would randomly stall, I would get the same pcodes: p0010 p0020, 2 evap codes, readiness code, o2 sensors and p689.


Haha, at least you figured it out. Mentioning codes would have made it a lot more easy to diagnose.
 

CJ-

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Haha, at least you figured it out. Mentioning codes would have made it a lot more easy to diagnose.

In hindsight, yes. In the moment when I posted the first message in the thread, I will admit that I was a bit frantic and sweaty from all the stalling on the way to work and not having functional air conditioning, hopefully the Short was the issue so I could focus on why my ac constantly clicks on and off.
 

rickf

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You are going to want to get that wire sealed up or it will corrode internally and give you all kinds of false readings. And that does not explain the extremely low baro reading. Unless the last time you went WOT was in Death Valley.
 

CJ-

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Update, day 4. Stalling came back, tried moving the o2 wire and wouldn’t stay running longer than a minute. Decided to take it to the dealer.

After a day of troubleshooting, hair being pulled out... the tech at the dealer figured it out.

One of the diodes under the hood in the fuse box was intermittently failing. On my 05 GT, there are 2- 1.0 amp diodes and the tech was somehow able to test the diodes and discovered one of the 2 diodes had been failing intermittently, the service writers exact words were “the tech tested the diode and found out sometimes it’s working and then it stop, the working again, so he replace it with a new one and your car stopped stalling, he drove the car a lot to make sure that was it, he let it idle for along time too and no more stalling”... so I picked her up, paid $144 for the service and I’ve been driving here everywhere since Thursday and no more stalling. Yay! Hopefully this post will one day help someone and save them a lot of headache by knowing a simple 1.0 amp diode cause so much grief and could be replaced by anyone for probably less than $10 and 1 minute of spare time.
 

Pentalab

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Update, day 4. Stalling came back, tried moving the o2 wire and wouldn’t stay running longer than a minute. Decided to take it to the dealer.

After a day of troubleshooting, hair being pulled out... the tech at the dealer figured it out.

One of the diodes under the hood in the fuse box was intermittently failing. On my 05 GT, there are 2- 1.0 amp diodes and the tech was somehow able to test the diodes and discovered one of the 2 diodes had been failing intermittently, the service writers exact words were “the tech tested the diode and found out sometimes it’s working and then it stop, the working again, so he replace it with a new one and your car stopped stalling, he drove the car a lot to make sure that was it, he let it idle for along time too and no more stalling”... so I picked her up, paid $144 for the service and I’ve been driving here everywhere since Thursday and no more stalling. Yay! Hopefully this post will one day help someone and save them a lot of headache by knowing a simple 1.0 amp diode cause so much grief and could be replaced by anyone for probably less than $10 and 1 minute of spare time.

What diodes ? What are they used for exactly? Are they steering diodes, so the signal doesn't back feed onto something else? A 1.0A diode cost dick. 3A and 6A diodes have surge ratings of 200/400 A respectively..and are bomb proof. Your typ 1.0A diode has a surge rating of 20-30A. I buy all 3 types by the hundreds for other applications..and those are all 1 kv PIV types. You can also series em for nore piv..and you can also parallel em for more current.... ( and also more surge current).
 

CJ-

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Well in the manual slot 53 is a diode for the PCM which I’m assuming is the one that was replaced, the other diode is slot 48 which is listed as A/C Clutch.
 

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