2003 F-250 5.4L 160K miles

The engine maintenance light is NOT illuminated.

The engine stumbles, runs rough, for maybe 2 to 3 minutes after cold start only. It doesn't stall but feels like it is close to it. After a few minutes, it smooths out and runs normally.

The engine is no where near warm when it smooths out, it runs rough for only a very short amount of time.

It has been doing this at every morning cold start for the past 2 weeks.

What engine control mechanism is at use for the initial couple of minutes only? I suspect that's where the problem is.

 

my first guess would be the MAF sensor. I would check your air filter and see if it is clean or not, if it is really dirty change it. The next step I would try is go buy some MAF cleaner and then pull your MAF sensor out and clean it and put it back and then try it. Make sure you buy MAF cleaner, do not use break cleaner or carburetor cleaner to clean the MAF or you will ruin.

Try that and see if it helps

 

My 2006 5.4l (only about 64,000 miles) would do that too occasionally in the winter.....sounded like it was coughing and trying to "catch". It would always smooth out though before I drove it; never did it while I was driving.

I never did anything to fix it. Hasn't happened again for awhile now.

 

Thanks for the replies. Just inspected the air cleaner and MAF sensor and all looks clean but I went to Autozone and bought some CRC MAF cleaner anyway. I'll clean it before I start the truck tomorrow morning and post back what happens.

 

Sounds like a bad IAC valve to me. You can take it off and try cleaning it first.

 

An important point is that the motor purrs like a kitten and idles perfectly except for the first couple of minutes in the morning when it feels like it is misfiring, bogs down, and just doesn't want to go. If something was clogged, wouldn't it happen all the time?

The truck can sit for 4 hours and start-up fine. It's only after it sits all night.

Moisture??

 

Think of the IAC as sort of the modern day equivalent of the choke (not a direct relation, but similar). Once warmed up it's almost unneeded. Another quick diagnostic (which isn't 100% accurate) is to run your a/c. If you notice a harder than normal engine surge when the compressor cycles, or if it stalls completely when it's a cold start, that could be an indication of the IAC giving out.

 

Check your air filter too - i get critters in there leaving nuts and crap. That shouldn't get past the filter, but it's a good idea to keep it cleaned out. Had a mouse chew through my tractor filter last year.

 

I would check the IAT sensor.

 

Success! Thank you Pocketlint, your diagnoses of a dirty MAF sensor was correct.

For those that don't know, the MAF sensor is inside the air filter housing. Take it apart as though you were going to change the air filter. Just inside the half attached to the motor is the MAF sensor sticking out into the air stream. It has two apparently uninsulated, exposed small wires. Spray those with MAF cleaner or an electronics cleaner, not carburetor cleaner or something similar. I bought a small can of MAF cleaner at Autozone. I did not touch the wires with anything except for a few spritzes of the spray.

When I inspected the sensor before cleaning, it appeared clean but I sprayed anyway and now the motor runs fine after the morning cold start.

BTW, I did not have to remove the MAF sensor from the air filter housing. The whole job took about 10 minutes.

Thanks again to all who replied. Saved me money and time. Gotta love the Internet!!

 

Glad to see that it's running better mikestable