Because that's the built in rev limiter safety so no one can over rev the engine in neutral. I suspect that both of these problem might get solved by replacing the Neutral Safety Switch/Range Sensor down on the tranny. The other possibility is it's connector is dirty, broken, or corroded.

 

Allor where have you been. You might be on to something here. Whoops, don't want to boost his ego . There is something to what he is saying, google it and there are a few topics that pop up. PRO DIY and R&T try it in Neutral and Park and see if the limiter kicks in at 3000 RPM. It should stumble a little drop to about 2700 RPM and then bounce back up and repeat it self. Is this what happens when you are driving. If so, you may have found your issue. Now, you have find the problem. Neutral Safety switch, possibly, how about PCM?

 

In post #23 when I was testing the fuel pressure I had run the rpm up to 3k in neutral and did a short burst up to 4k.
The problem is somewhat load/hill dependent causing the power to drop off from around 2600 to definitely by 3000 rpm.
I have had the SES start blinking on a long mild hill at 2400 rpm.
At 3400 rpm I can feel it surging a bit.

 

Sometimes I just have to pull back and let everyone wander around aimlessly searching for answers. This helps them appreciate me more when I come back and start offering advice again.

 

Alloro, that kind of mean. You have all the knowledge in the Expedition world and you won't share it with others!

R&T - I think you may have another problem. I wonder if you have a mis-fire under load going on. That would mean cop/plugs. What happens when you do it Neutral or Park? Same thing or does the rev limiter kick in.

 

my 2000 expi is doing the same. changed all egr components, plugs, o2 sensor, and checked cat converters, to no prevail. was also told to check fuel filter. i'm getting egr flow insufficient, and missfire codes. need help.

 

All the plugs/COPs are new and it's not chugging like a misfire. The lack of power above 3k rpm came in after replacing them. It idles and runs great under load up to 2200 rpm.
Today had something new happen. Took it out for a trip, got on the freeway with a mild incline and tried to accelerate slowly up to speed. At 2200 rpm the SES came on solid. Was able to get up to about 55 mph @ 2600 rpm and no more power. Up and over the hill the SES started blinking and cleared by itself after a minute or two. Made a couple of stops and accelerated moderately up to 3000 rpm where the road opened up and the SES came on again. At the next stop read/manually cleared the codes - P0174-Bank 2 lean, P0301-#1 misfire & P0303-#3 misfire. All Bank 2 or right side engine codes. On the trip home the hill is steeper, went up at 45 mph @ 2400 rpm, but no SES or codes.

 

Bank 2 would be LEFT (driver's) side.

My SWAG is you havea fuel supply issue.

Your earlier post sounds like you were doing fuel pressure checks in neutal/park. It doesn't need a whole lot of fuel to run 3000 rpm in neutral. Pulling a grade is a whole different animal. You need to check fuel pressure when the power drops off.

Duct tape your fuel pressure gauge to the windshield and check the pressure when it starts to lose power.

Surging or running out of power (to me) is insufficent fuel supply. Too lean a mixture (because of lack of fuel) will cause a misfire, and the misfire will dump unused oxygen out the exhaust. The PCM will interpret the excess oxygen signal from the O2 sensor as a lean condiction.

 

Oops, I'm not used to "banks".
My first car was a '66 Mustang I bought from my dad. It was his work daily driver.
Our family car was a 4-door '57 Chevy Bel Air.

I see your point about checking the fuel pressure under load.
Went out this morning and taped the gauge to the wipers.
Connected the gauge after sitting overnight - 0 psi.
Key on - 50 psi.
Engine on - 55 psi.
Took it out for a drive and tried a few times to get it to 3500 rpm - 55 psi.
Engine off - 50 psi.
Got a P0301 and 2 "pendings" (blinking SES) that cleared before I could read them.
The pressure readings held steady this time. Last time they were fluttering between 50 and 55.
Seems like the fuel pressure is not the problem.
Need to run the vacuum test, but I'm still trying to find my vacuum gauge.
We built a new garage/shop and moved my packed 2 car garage to the new one.

 

FYI - Bank 1 is always the side with cylinder #1, whether it be the driver or passenger side.

 

Bought an 06 Navigator that was doing the exact same thing. No codes, drove fine but when you really got on the gas it would stumble and lose power. Fuel pressure was good, coil packs were good. Beat on it hard enough to get a flashing check engine light once and the stored code was misfire cylinder 3 and 8. It had 89k miles and after surviving the dreaded spark plug change(none broke, just loosened them a 1/4 turn, sprayed seafoam deep creep in each hole, and took my time) and guess what, the old plugs were worn out, and with the new ones in, now it runs like a top again.

 

I changed plugs/COPs at 120k when #6 & #7 got rusty springs in the COPs and started misfiring. The plugs definitely were worn and it ran great after changing them. Now when I can get on it hard it starts to pull great, but then loses power at 2600 rpm. It seems to be getting worse.

Got a vacuum gauge and at idle it's pulling a solid, steady 19.5 inches.
When I slowly raise the rpm in neutral it will drop to 15 inches at about 3k rpm.
Took it out for a drive and when it's steady at 2k rpm it reads around 10-15 inches.
Take it up to a steady 3k rpm and it reads 2-5 inches.
I'm wondering if one side precat/cat is clogged.
If one side of the exhaust cat or precat is clogged how would that affect control of the engine?
Is Ford the only place to get a Calif approved cat for the 5.4l '03 Exped?

 

Or maybe both sides are bad. Or maybe all the cat particles are now residing in your muffler (but then I'd think it would throw a P04xx code).

You haven't mentioned it in your previous posts, but your air filter isn't plugged, is it?

Anyway, I think you are getting close to the problem.

 

Air filter and ducting are all clear. I checked that early, as in maybe a grocery bag had been sucked into the tubes.

 

Guys, i have a 2003 5.4 with the same issue, replaced COP plugs Fuel filter, and still have the sluggish power @ 3000 RPM. Could it be the Speed Sensor in the Tranny? Even Replaced the EGR sensor and vac lines. Seems to have started with that went bad, and the vac lines worn out. I have 200,000 miles on it and love it, just want my power back. I am getting the code for Lean Bank 1.

Any help appreciated.

Thanks