2004 fx4 5.4
Took a trip, and stopped for gas! When I started the truck back up it would not idle. It keeps stalling. The truck has more power now than it ever has but it shuts off when it idles in park. Code said mass air sensor is out. I love the extra power which I don't understand, almost makes me want to leave it alone, but I hate that the truck shuts off! Would the sensor faulting give me more power? My fuel mileage didn't change!

 

Autozone will pull codes for free.

 

Looks like he knows what the code says already...

 

Did someone install a nice set of cams for ya while you were filling up that you might not have noticed?

 

If your throwing a MAF code and it's running like crap at idle with added power, then you are more than likely running LEAN. Check and make sure you have no vacuum leaks first. If not, more than likely the MAF took a dump (or starving for fuel). Running lean is bad. It can and will cause damage. Cylinder temps get very hot and it can burn holes in the pistons and/or valves. It will also foul your spark plugs. I recommend getting it fixed ASAP.

 

i work in the gas business, reg gas sometimes has ethanol, this stuff is garbage unless ur engine is e85 ready, ethanol runs uptoo 30% leaner than regular gas,now thats not enough to make the engine run that bad but combine it with something else like a dirty mas sensor and it can reek havoc, super can not have ethanol because it could destroy a 2 stroke engine, so i would try and fill up with super and see if it helps.

 

Would cleaning the throttle body help?

 

Clean your MAF Sensor!

disconnect the battery

unplug the maf on the top right of the stock air intake

2 bolts, safety torx bits (size t20, i think) You can get a cheap set of safety torx bits for $7 at an auto store

don't touch the maf internal wires

spray 15-20 sprays of CRC brand MAF cleaner inside the square holes directly onto the MAF wires (use no other cleaners!) (~$6)

let it dry for 30 min with the battery unplugged to reset the computer

plug it back in (use dielectric grease on the plug) and your idle will be fixed (or you might need a new MAF Sensor)


*get the codes to confirm before buying parts.



BTW: if you want to narrow it down to the MAF, unplug it, crank the truck - if it idles fine, then you know the issue is MAF related. (unplugging it sets the computer to the default mix)

 

You're right techrep, I didn't pay attention, like I do when my wife talks to me. LOL

tekmunkie has the right idea. That will tell you if it's the problem.

 

It was a vacuum leak! The main line for the 4x4 going to the back of the motor had came off. Who knows how?! It was a pain to get it back on. Very little room to work, I had to move my fuel rail out of the way so I could get my hand back behind the motor! My front axle was locked in for about 100 miles of the trip. Diff fluid needed replacing anyway! Anyways the truck idles normally again! By the way my MAF sensor was under a warranty so I replaced it anyway!!