quote:

Originally posted by Shifferbrains:
RBeach,

Make sure that the snorkel from the air cleaner to the intake is properly seated and tight, and there are no splits that can allow unmetered air into the engine.

I have confirmed this as that was one of the first things I was looking for.

Check the PCV and the hose going to it

Back to the basics.
You mentioned the truck sitting around for a few months with the tank almost empty.
Have you run some dry gas through it in case some moisture got in there?
Kind of like chicken soup. Can’t hurt to try.

Ford trucks of the 2004 - 2008 vintage had a fuel pump driver module (FPDM) mounted on the cross member above the spare tire. Water, crud, and mud get slung up there, and the bottom of the module gets eaten away exposing the electronics. Causes all kinds of problems. It would be worth checking.

Look at the VCT variable camshaft timing solenoids on your truck 4.6L & 5.4L. This could be part of the problem. My 07' F150 started slowly having idling issues when slowing down or creeping along in bumper to bumper traffic. Got to the point that would start shaking like the engine would come out of the truck, but a tap on the gas would get it back to normal. Seems these valves get stuck or the screens get damaged and fail. On my 5.4L Ford changed the way these were accessed sometime during my model year. Went from a 15 minute DIY easy access through the valve cover, to a tear the engine apart and pay $800 bucks endeavor. A pair of them (OEM) should only be about $70 for a pair online (Rock Auto, 1A Auto, Parts Geek, etc). Ford dealer or online will charge about $70-80 per piece.

quote:

Originally posted by 1Lowtrk:
Check the PCV and the hose going to it

New Motorcraft PCV valve and hoses checked. All were good.

quote:

Originally posted by 220-9er:
Back to the basics.
You mentioned the truck sitting around for a few months with the tank almost empty.
Have you run some dry gas through it in case some moisture got in there?
Kind of like chicken soup. Can’t hurt to try.

Yes. The tank was emptied and new gas put in.

quote:

Originally posted by Muddflap:
Ford trucks of the 2004 - 2008 vintage had a fuel pump driver module (FPDM) mounted on the cross member above the spare tire. Water, crud, and mud get slung up there, and the bottom of the module gets eaten away exposing the electronics. Causes all kinds of problems. It would be worth checking.

This was replaced as well.

quote:

Originally posted by sig226fan:
Look at the VCT variable camshaft timing solenoids on your truck 4.6L & 5.4L. This could be part of the problem. My 07' F150 started slowly having idling issues when slowing down or creeping along in bumper to bumper traffic. Got to the point that would start shaking like the engine would come out of the truck, but a tap on the gas would get it back to normal. Seems these valves get stuck or the screens get damaged and fail. On my 5.4L Ford changed the way these were accessed sometime during my model year. Went from a 15 minute DIY easy access through the valve cover, to a tear the engine apart and pay $800 bucks endeavor. A pair of them (OEM) should only be about $70 for a pair online (Rock Auto, 1A Auto, Parts Geek, etc). Ford dealer or online will charge about $70-80 per piece.

I had a friend I was trying to troubleshoot over the phone with and he mentioned the same thing. I cannot find the VCT solenoids on my engine. I have the 2V and not the 3V engine.

quote:

Originally posted by sig226fan:
Look at the VCT variable camshaft timing solenoids on your truck 4.6L & 5.4L. This could be part of the problem. My 07' F150 started slowly having idling issues when slowing down or creeping along in bumper to bumper traffic. Got to the point that would start shaking like the engine would come out of the truck, but a tap on the gas would get it back to normal. Seems these valves get stuck or the screens get damaged and fail. On my 5.4L Ford changed the way these were accessed sometime during my model year. Went from a 15 minute DIY easy access through the valve cover, to a tear the engine apart and pay $800 bucks endeavor. A pair of them (OEM) should only be about $70 for a pair online (Rock Auto, 1A Auto, Parts Geek, etc). Ford dealer or online will charge about $70-80 per piece.

The 2006 F150’s with the 4.6l engine don’t have variable cam timing.

I have no actual experience with your engine but I would suggest checking for a clogged fuel filter (if equipped) or catalytic converter.

Clean the throttle body. It’s easy. Look it upon YouTube. I used to have one and this did it after replacing everything.

Long shot here....I just had acceleration issues with my Ford ranger and after changing a lot of the parts you mentioned i finally figured out that it was the A.C. System was low on Freon and the compressor was causing the engine to surge. If you run your air system in defrost mode it.might be a cause.

quote:

Originally posted by smithnsig:
Clean the throttle body. It’s easy. Look it upon YouTube. I used to have one and this did it after replacing everything.

Any time I have any issue, the first thing I do is get some carb cleaner and spray the heck out of and around the butterfly in the intake. I had a car with "stumbling" issues years ago and a mechanic friend told me to do that. (over the phone, he'd never seen the car) I did and it went away. Something so simple. In the decades since, it cured a problem a second time. Now I do it as a matter of routine maintenance.

quote:

Originally posted by smithnsig:
Clean the throttle body. It’s easy. Look it upon YouTube. I used to have one and this did it after replacing everything.

I did this when I changed the throttle body gasket. Cleaned throttle body to like new condition when I had it off, and cleaned inside intake as far as I could.

quote:

Originally posted by ibexsig:
Long shot here....I just had acceleration issues with my Ford ranger and after changing a lot of the parts you mentioned i finally figured out that it was the A.C. System was low on Freon and the compressor was causing the engine to surge. If you run your air system in defrost mode it.might be a cause.

Freon is good. System was checked this past Summer. Plus, system is turned completely off most of the time.

Having once designed Ford EGR valves, from 1984-1992, I can tell you that Ford went to a lot of trouble to prevent carbon deposits in the valve to cause it to either stick closed or leak.

It sounds like the problem occurs when you go "closed loop" as you mention after it is warm, the problem is evident. Before closed loop condition is reached, the A/F ratio is richer, and runs this way to prevent stumbling when cold.

If the EGR valve diaphragm is cracked, it would be a continuing source of a vacuum leak, if vacuum is requested by the controlling solenoid. But, it would not be opening the valve either.

If for whatever reason a carbon crust in the body of the valve is holding the pintle off its seat, the recirculation of exhaust gas can reduce the available oxygen for combustion, as it has already been combusted and has a bunch of vile chemical compounds in it (HC, NOx). This might be the cause of a sag in power.

The gasket back then was a carbon-coated thin sliver of metal that approximates a utility knife blade. Be careful.

For many years, all Ford engines had EGR. Then, advances in pollution control meant that only California engines had them. Not sure if yours has one or not, but it may not be fun to take off the supply pipe to the valve body. It is kind of like a plumbing fitting with a rotating nut surrounding a flanged pipe that seals against the valve inlet internal flange.

quote:

Originally posted by 4MUL8R:
Having once designed Ford EGR valves, from 1984-1992, I can tell you that Ford went to a lot of trouble to prevent carbon deposits in the valve to cause it to either stick closed or leak.

Interesting.
When I was in the car repair business, I gained a lot of experience diagnosing Ford EEC-IV driveability issues.
EGR and EVP fault codes and problems were pretty common, particularly on earlier models.

Some aftermarket company even came up with an EGR valve gasket with a screen built in to prevent carbon chunks from jamming the valve partially open.

Replacing the EGR did not solve the issue.

I added fuel injector cleaner and Heet and changed fuel filter again out of curiosity. With all of this done, the stumble is not as bad (very minor), but it is idling like a muscle car with an oversized cam.

quote:

Originally posted by Shifferbrains:
Since you have the Maximus, graph the MAF, both upstream O2's, and if you can both ST Fuel trims. Drive the truck, and from a stop take off smoothly to WOT and watch the graphs. The MAF, O2's and fuel trims should go high, pretty much mirror each other.

I did that and took 2 short videos of the screen with my phone, but I cannot upload them.

The MAF started in the high range at idle (5.11 with a 2-6 g/s range). As soon as I gave it gas, it shot through the roof, maxing out at 187 at WOT.