Bucking Ford F150

I have an '03 Ford F150 with the Triton motor. About 2 weeks ago it started acting like the motor was “cutting out”. We changed fuel filters, got a fresh full service, got the alternator checked and did visual on the drive line and rear end ( did have a mechanic check it also). The “check engine” light does not come on while it is acting up (it does light when starting so I know the light works). At first the truck only acted up when it was good and warmed up, but now does it all the time. Does anyone have any idea whats wrong?

I would have the fuel system checked out by a good mechanic. Start with the fuel pump pressure. An engine that is fuel starved will “buck” like a bronco and probably will not throw a computer code.

How many miles are on it? How old are the spark plugs and wires?

Try to be more specific about the conditions under which it bucks. e.g. How does it run at idle? Is it associated only with certain speeds/transmission ranges? Only while accelerating? Cruising? Coasting?

140,000=/-mi, bucks on acceleration(can both power out of it and release acceleration to get it to stop bucking), idles smooth, starts bucking 40-50mph but not consistantly (has happened at 35 and 65). I was told by Ford garage not to worry about tuning it up until the check engine light come on due to the coilpaks.

Again, and as cigroller had asked, how old are the plugs? Aged plugs and poor connections in the coil boots can cause stupid things to occur.

Has anyone bothered to scan the truck for codes yet? The CEL does not have to be on for codes to be present and the advice given to you by the Ford garage is pretty poor. Never put much faith into what counter people tell you. There are some good service managers and writers but they’re in the distinct minority.

I agree with ok4450 that plugs & wires are suspect, and that the advice is absolutely terrible. Not only are plugs and wires just routine maintenance that should never be left long enough to create problems, but why would someone say or assume that eventually the coil packs would produce an engine light? That’s all just weird.

Checking fuel pressure under load and for exhaust restrictions is also something you should do or have done. However, if the bucking issue is somewhat unpredictable I’d be much more inclined to assume and ignition issue. I’d lay a #2 guess on fuel pressure issues.

Since you say the bucking starts at 40-50mph, one thing that should also be considered is the question of a torque converter clutch lockup problem. These can feel a lot like bucking/misfiring.

I’ve had the truck since 2005 and have never changed the plugs and wires, again because 3 service managers & even more mechanics and a shop teacher at the local tech school (also a master mechanic with 30 yrs of experience) have said not to. I drove it today (1st time for me in a week) because when the fuel pressure guage was hooked up air came out of the line and the truck behaved like it should. The truck runs and idles like a dream. When hooked up to the computer there were no codes.

cigroller commented on the torgue converter clutch lockup, is this a fairly common problem?

At 140K a TCC lockup problem would not be unusual. On many vehicles there is something like an OD Off button - something you might use in a towing mode. Sometimes that disables the TCC lockup. If you have such a button you could hit it and see what happens. Sometimes the TCC lockup is also disabled in something like “3” instead of “D” on the transmission selection. Of course, I never even asked if it was an auto trans. If not, this is irrelevant.

You are getting terrible advice on the spark plugs (as noted more than once). Replace them. Since you have never changed them you have spark plugs with 10 years and 140K on them. They are junk! You need to do this even if it doesn’t solve this problem.

It could also be due to an intermittent fuel pressure sensor failure and even a fuel pump going in and out.

That plug advice is horrible and hopefully when they are removed the plugs won’t bring every thread in the heads out with them.
I would suggest that you do some reading up about even removing the plugs on Tritons, much less any plug thread repair that may be needed. A prayer along the way may help too.

You know - it did just cross my mind about the Triton spark plug replacement issues. I’ll bet that’s where the really bad advice comes from - no one wants to touch those things with a 10ft pole, so they’ll pretend you don’t need to do anything with them. Indeed, follow OK’s advice & read up on it a bit. But it has to be dealt with. You can’t just drive around with 140K spark plugs at all - let alone while scratching your head about why it might not be running right.

ok I will definately keep looking for a mechanic to change plugs and wires. yes I have an automatic tranny. I turned the od off and on but it happened more often with it on than off. Wouldn’t the fuel pressure sensor show up when we hooked up the guage? I drove it 72 miles with the guage on and the pressure never went below 30lbs, even with the truck off it held 40 lbs for 20 min then we released it. The truck idles and runs smooth which is why I question the plugs and wires, but I will get them changed as I did read up on them and it isn’t a task I think I would be comfortable doing myself.