I hope someone can help. My mechanic cannot figure it out nor can a Ford mechanic. About every one to two weeks, only in the morning, after I drive about a half mile it starts running rough and stalls at idle. It behaves like it is flooding out. When I can get it started black smoke pours out until it clears. I can hold it above 2000 rpm but, as I lower the revs, it starts stalling again until it stops. I've tried blowing it out on a long stretch but at normal speed it does it again. After repeating this several times it suddenly runs right and won't happen again for a couple weeks, the longest being four weeks. I thought it might be the remote start but that theory was busted. I've searched here and in other sites and replaced the IAC but it still did it. Replacing the O2 sensors did not help. I don't want to keep throwing parts at it. Any ideas folks?

'03 F250 FX4, 5.4 gas

 

Any codes?
A stuck open injector might do this on occasions.

 

No codes. Mechanic kept it a couple days to try it out with his code reader plugged in but of course it ran fine. We both agreed that it's not an injector because it would run rough but wouldn't die particularly because it's an 8 cylinder. Also very hard to restart and until it clears out with a black cloud. One injector shouldn't do that.

 

In reference to the injectors, I should have said "it SHOULD run rough but SHOULDN'T die".

 

It sounds like a fuel pressure problem to me. Check the fuel pump. How much pressure is it producing? I'm not that familiar with the 03. Does it have a throttle body injection or regular injectors? It may be something in the fuel return line if it has one. It could be a bad pressure regulator. Could be a bad mass air sensor. It would tell the motor to add more fuel. Look for cracked intake tube or bad filter. Its in the fuel system for sure.

 

Bone, mechanic doesn't think it's the fuel pressure. Feels the injectors would prevent it from flooding. don't know if they're regular injectors or throttle body. Maybe someone here can answer that. A bad fuel filter would reduce fuel flow and wouldn't flood it. air filter is good. Cracked intake would make it run lean. I'll run your suggestions by mechanic.
Thanks

 

Disable the vent recovery/purge system entirely and see if that stops it. If you are looking for something that sucks in a big slug of I-don't-know-what all of a sudden on purpose, that would be it. If you would like the culprit to be also hooked to the gas tank, you're in luck there too. Since it takes a month or two to be sure, your test has to last about a month. It'll just vent through the carbon bed for a month, but it's January and that shouldn't really hurt anything. It'll set a code for flunking the vent system testing, I think.


You could use a fuel pressure gauge, but I don't think you'll learn anything, and you need that hooked up for a month too.


I do not agree with presuming it's not a stuck injector based on thought experiments, but as you know, it won't be easy to troubleshoot that. P.S. It has 8 fuel injectors, but as usual, they're all in the intake manifold.

 

I'll run it by my mechanic and let you know. Thanks for the advice.

 

Vapor canister full?

 

The vapor canister never came up in conversation. I'll pass it on to mechanic. thanks.

 

Okay, mechanic and I agree that it isn't a cracked intake tube, filter or vapor canister. The problem would happen all the time. There is no port for hooking up a fuel pressure gauge and still drive it. They disconnect the fuel line, hook up the gauge and turn the key on to measure. no fuel going to injectors. We still don't think it's an injector. It shouldn't flood out to the point of not running if I keep goosing the accelerator but it does. It won't stay running even at 2k rpm when the problem occurs infrequently.
How do I disable the vent recovery/purge system?

 

Sound like either a bad vapor canister and or related solenoids or valves or a bad fuel pressure regulator. I have seen 2 pressure regulators that acted up (dumping raw fuel int intake) only occasionally for quite a while before failing completely. When thy worked there was normal pressure and no other signs of a problem, the owner wasn't able to find the actual problem until it failed completely and he was a Master Certified Auto Tech.

 

The main fuel control on that engine is the MAF sensor,,,it richens the engine with air flow and can richen it to the point of stalling..that being said the canister and the regulator also mess with fuel. With no codes its gonna be tough to figure out.

 

Interesting idea there. Errors on the MAF would be easy enough to spot by driving with a scan tool connected to the OBD port, monitoring data in real time, all the time.


It needs to be hooked up for a month.

 

The problem with Fords is they don't throw codes unless the problem happens for a while where other makes will send a code right away. I have a scan tool coming and will run with it so hopefully it'll pickup something if the flooding happens again. It hasn't occurred in over two weeks now so we'll see.