Triton V-8 on drugs?

[Ufatz]

I have a nephew who knows everything-you guys know the type. Here is the problems; 99' Ford F-150 with Triton V-8. Oh, it's white.

Started running erratically....up rpms and then down almost to dying. Been doing it since early yesterday. Mr. knows-all=auto things says it is some bad gas.

I nod while stifling a giggle. I say, and I have no familiarity with that engine, that something in injection system has failed. Perhaps something as easy as an electronic bit of some kind.

I am going to take care of the truck for the kid but would like to hhear any pre-dealership diagnostics you guys can provide.

[RuddyDuck]

Is it throwing a code? Is it a 5.4 or 4.6?

Not a mechanic, but I do have a 2000 Ford Exp with the 5.4 in it. I have had the coil on plugs go out. This usually just makes it miss alot, but it did chug pretty good sometimes before I got that fixed. Didn't really go up and down like your nephews is doing. It will throw a code for this saying what one is bad.

I just put a new EGr valve it in it yesterday. It was throwing code P1405 for this. Missing once again was a symptom of this and stuttering at low speeds or in overdrive.

Another common issue with these is that the passenger side exhaust manifold bolts break off(the back two). Mine has this, but has been ok. Talking to a mechanic friend of mine, this can also cause issues sometimes if it gets too bad.

Good luck.

[Jeremy airjer W]

Vacuum leak?

[Macgyver55]

Vacuum leak?

That's what I would think too! Likely the large rubber elbow fitting on the rear of the intake manifold.

Can be a little tough to visually inspect unless you crawl right up and on top of the motor.

[Jeremy airjer W]

Or carefully maneuver a hand back in there while the engine is running and feel around all the vacuum hoses. If you hear or feel a change in sound or how the engine is running than your on the right track.

[Ufatz]

I have not actually driven this truck but I heard today that he used it and drove it 20 miles or so and it ran normally. Makes me wonder....intermittent up and down...you guys may be onto something with lose or leaking vacuum line? Or Idle Control Valve?

Dontcha just love automotive puzzlers!?