Loss of power/stumble then dies

[race4beer]

Hi,
Started having an issue with my 03 Expy (5.4 4WD) recently. I've searched and have found a previous thread, but it's very old so I was asked to start a new one.

Last week I was running about 70MPH when I suddenly had a loss of power and the RPM fell to around 300. There was no throttle response at all, but eventually it came back to life and ran fine. 2 days later the RPMs dropped to about 300 again and the battery light came on. The motor sputtered for about 10 seconds and then died, while it was sputtering, there was zero throttle control. Restarted fine and ran great. Now it's happening a couple of times a day, and each time a restart will clear the issue. Other than the battery light, no other lights come on, and nothing else seems out of the ordinary.

It's Drive by Cable, and I've removed and cleaned the throttle body and replaced the TPS to eliminate that from being the issue but it's still happening.

I've read several articles online of possible PCM Issue, Fuel Pump, TPS, grounds, etc but I was hoping to find someone that has had the issue and been able to correct it or at least isolate it to one system.

 

[BRIANGEE]

Have you checked for any codes?

 

[Bedrck47]

How many miles on the expy?
Has the fuel pump ever been replaced?
Has the fuel filter been replaced?
Has the fuse box ever been replaced? The fuel pump relay on the fuse box is a common problem with the 03 and 04 expeditions

 

[race4beer]

No codes present

190k, got it with 150k, I don't know for sure what was done before.


I've done Coils, Plugs, Fuel filter, Intake

Runs like a champ, then this started out of the blue.

 

[docraymund]

No power means fuel supply was interrupted for a brief moment especially if it occurred after hitting a bump or a pothole. Check wirings pertaining to the fuel pump and see if you can duplicate the problem.

 

[Bedrck47]

From your description of what is happening it appears that the fuel pump relay is beginning to fail

There is a very good video on you tube



Pay attention around the 6 minute mark in the video where he is pointing to a dark green/yellow wire.


This is part of the fuel pump relay contacts There is a way to bypass those contacts to see if your problem is being caused by the FP relay Let me know if you would like that procedure

 

[race4beer]

From your description of what is happening it appears that the fuel pump relay is beginning to fail

There is a very good video on you tube



Pay attention around the 6 minute mark in the video where he is pointing to a dark green/yellow wire.


This is part of the fuel pump relay contacts There is a way to bypass those contacts to see if your problem is being caused by the FP relay Let me know if you would like that procedure

Thank you, I'm not dead in the water yet, but I'm at a point where it's dropping out at least once in my commute and making for a pretty scary drive. I think I am going to rig up a small light to the green/yellow and see if when the issue happens I lose power to the bulb (and pump). That green/yellow is the correct power reference to use?

 

[Bedrck47]

yes I am sending you a PM check your in box in a couple of minutes

 

[race4beer]

yes I am sending you a PM check your in box in a couple of minutes

Thanks

 

[dimension12]

Have you solved your problem yet?

 

[race4beer]

Have you solved your problem yet?

I've been traveling and haven't had the chance to check into it any further, hoping to look at it next week.

 

[dimension12]

I am working on the same issue on a 99.

 

[Bedrck47]

I am working on the same issue on a 99.

You should start a separate thread in the first gen section since yours is a 99 and the OP in this thread has an 03

Post and list your problems and any codes you may have You will get better results and responses dealing with your problems Explain in detail what the problems are

 

[race4beer]

I am working on the same issue on a 99.

There are a couple of YouTube videos on bypassing the fuel pump relay that were informative. Going to try that and see if it stops, and then fork up the $350 for a new fuse box if that's the issue.

 

[Bedrck47]

Again There are some differences between the 1st and 2nd gen expys when it comes to the fuel pump circuits and fuse boxes What may apply to one generation may not apply to another generation expy

 

[dimension12]

I have a thread in the 1st gen area.

 

[race4beer]

I've been traveling and haven't had the chance to check into it any further, hoping to look at it next week.

On my 12 mile drive to the airport last week it died 5 times, including once when I was crossing 3 lanes to get my exit! When I got back I bypassed the relay so I can drive it while I am waiting for the fuse box to come off backorder at Tasca. Since I bypassed the relay I have had zero trouble.

Should have the new fuse box in a couple of weeks.

 

[dimension12]

Glad to hear.

 

[Fawkes]

Glad to hear that it seems to be the relay and that you were able to temporarily bypass it.

I had similar symptoms a while back. The oil level was severely low, and after filling it up, the problem went away. I assumed that it sensed the low level, and went into limp mode or something.

 

[race4beer]

Checking back in, $350 later and it's fixed. Replaced the fuse box and problem has not come back. Appreciate all the help!