5.4 Triton goes kerchunk....kerchunk...

[Radio]

OK here's the deal.

For some time now, intermittently, the F-150 5.4 Triton will sputter. The road speed is always about 45 and the RPM is right at 1200. It's like it's not getting spark for just a moment and then we're back to normal.

I wonder if the throttle position sensor is the culprit.

It'd be nice if that were the problem since it's only about $60 and right up there on top where I can reach it.

Heard a rumor the TPS is built permanently into the throttle body and you have to swap the whole thing. Any truth to that??

[NN5I]

If you don't own a code scanner, get one. They're inexpensive, and there may be a stored code that would shed light.

If you don't own a factory service manual for your vehicle, get one. It will answer questions like the one about the TPS. Typically the whole set is about $100 or less. One of the most reliable vendors, other than Ford itself, is Faxon, www.faxonautoliterature.com from whom I have bought many factory service manuals. Good luck.

[N3LYT]

A lot of auto parts stores will scan it for you for free. If you have no light it probably is not the TPS. You can check it with an ohm meter it does work so the resistance is not important but the response has to be linier no drop outs as it moves through the range open to closed.

[Radio]

A lot of auto parts stores will scan it for you for free. If you have no light it probably is not the TPS. You can check it with an ohm meter it does work so the resistance is not important but the response has to be linier no drop outs as it moves through the range open to closed.

Previous free scans have shown no codes set. There is no check engine light.
Since the scans are free, might as well try another tomorrow.

The NAPA store has ordered me a Haynes manual and i pick that up tomorrow. The situation is annoying but nothing more than that, and it doesn't ever happen when towing because the throttle is in a different place.

[NN5I]

If it always occurs at the same throttle position (rather than the same rpm as you originally stated), then perhaps it's reasonable to suspect the TPS. Testing it, as suggested by N3LYT, is pretty easy if you have an analog ohmmeter, though I'm unsure about his statement that it should be linear; but in any case it should be smooth and monotonic.

As for the Haynes manual, in my opinion it ain't a patch on the factory service manual. The Haynes manual usually covers multiple years and models and is much smaller. The factory service manual is for a specific year and model and typically is two or three rather thick volumes. No comparison.

[N3LYT]

If there is a glitch (flat spot or drop out in the resistance) it's bad and usually it will be in one spot only. You do have to move the throttle very slowly and you may have to try several times to catch it. When they get really flaky they will set a code but if you have a stumble from a bad spot on the board it won't. Fixing EFI can become expensive fast if you throw parts at it so it's best to be sure the part you are replacing really is bad.

[Radio]

Stopped by the friendly neighborhood NAPA store, which gives me a shop price because of my employer, and picked up a TPS.

Paid the fat kid in the shop next door $20 to stick in on for me. (It's just 2 hard to reach screws on a very hot engine. Boy did that kid sweat!)

On the brief 1.5 mile test drive home it didn't kerchunk once, and I can always get it to do that on the collector road between here and the state highway. Now prior, the tranny would not drop into 1st until you were about 20 ft from coming to a dead stop and it was kind of a thud when it did. Now it's nice and smooth on the downshift, in fact, it seems to shift much smoother in general.

The shift points seem to have moved a little, but I suspect the driveline computer needs to learn the new TPS curve and they will return to normal.

I guess the drive to and from work tomorrow will tell the tale.

[Radio]

OK so I couldn't stand the suspense of not REALLY knowing for sure, so I took the truck out for about a 30 minute test drive on rolling back roads, lots of 1200 RPM @ 45 MPH type terrain.

The old girl runs like new. Just perfect.

:driver:

[NN5I]

Cool!

[radiow6lar]

Glad you found the problem. I run a 2004 F-150, first of the "New" style. I replaced the throttle sensor about a year ago. I did not have your problem or ANY problem. The computer threw a code indication a throttle position problem. So I dropped in a new one just because. I've only gotten 86K miles on my f-150. On another subject, have any of you changed spark plugs yet? Original change out was supposed to be at 100K miles. I've done mine at every 20K miles. I also carry a special tool for removing the plugs if they break and separate in the head and leave the tip behind. So far never a problem. :D