This is what I have done I have 5.4 168,000 on motor . I have codes p0401 p0701 p0704 and some others .I can run truck for about 15min and it starts to lose power .I can't go over 1500 rpm . I have changed egr cleaned throttle body checked for vacum leaks changed the dpfe . new plugs . I have had a misfire code on number 1 but that code has stopped . I have put new fuel filter .I have a cheap scanner I use and it probably won't give me what I want also I changed down stream 02 sensors .

 

Identify your truck completely including year, transmission, and drivetrain.

You've spent a lot of money guessing....

Did you ever reset the PCM after doing any of those parts then retest to see what, if anything, comes back?

You'd probably do best to use a different scan tool or, at least, go back and read them again. Those P070x codes sound bogus.

 

2001 crew cab 4x4 auto and it has been frustrating .I also cleaned the maf with maf cleaner .I also have a higher idke after I cleaned throttle body I lowered the idke but the engine seems to idle higher than normal and when I slow down it takes a second for the idke to come down after transmission is shifting down .if that makes sense

 

How did you lower the idle?
701 and 704 codes don't apply to your truck.
Are you sure you listed the codes correctly?
Good luck.

 

I lowered it by the throttle body screw behind throttle cable .the code that keep popping up is p0401. It is just weird I can crank it up run it down the street for 15 min and then when I stop at light and start to give it gas it will pickup speed and when rpms hit 2000 it starts to back off on power so I let off gas a little and kinda push pedal less and get up to speed .then 10 min later I come to a stop and then give it gas I can only go up to 1500 rpm and it starts losing power it does back fire and if you try to push pedal down it wants to bog down and stall .I am almost leaning to fuel pump I will check pressure on tomorrow .but if anyone can come up with better idea ivsm all ears

 

Stewart, forgive me but you have no idea what your doing.
You never, I repeat never, adjust the throttle 'stop' on a fuel a injection engine from the factory setting.
Now you lost the proper airflow reference and to boot if too close to fully closed, the throttle plate can stick in the bore after the engine cools.
.
Have you looked up what the 401 code tells you?
It is a test failure when the computer does an EGR system test.
You need to understand what that means in the actual test.
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I don't know what is going on with the loss of acceleration but you must restore the throttle stop to at least near proper opening point so it will not cause additional problems and confusion.
For one it will mess up cold starts in cold weather if you don't.
Here is how you can get it back close.
With engine up to operating temperature, remove the IAC plug and adjust the throttle stop so the idle is about 550 +/- a small amount.
Put the IAC plug back on. if the IAC is working it should raise the idle to about 650/675 range on the Tach or better yet on a Scanner reading to be more accurate.
Then leave it alone. The idle is controlled by the program not an outside stop setting.
.
On the 401 code, it is a restriction of exhaust gas flow between the exhaust manifold and the ports behind the EGR. The test sensed it via the DPFE and reported it as out of limits. Find the cause in that system.
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After these are solved then go forward to look for a cause of poor acceleration.
Good luck.

 

I guess I just got my *** handed to me. No pun intended just I didn't know that I screwed up .I will reset it like you said. It was idling at 1200 rpm after I cleaned the throttle body .it was so dirty it probably had 1/16" of carbon inside all around it took me 2 hrs to clean the ports and everything. I figured the code p0401 was connected to the symptoms I have .

After reseting the throttle as close as I can what do I do next check fuel pump? The only other thing that is wrong is I have a small exuast leak .

 

If you have not done so, remove the IAC and uses spray cleaner inside until all gum and carbon is cleaned out.
Make sure the sliding valve is free to move using a small tool to move it.
This device controls air flow around the throttle plate as a means for the computer to control idle on a continuous basis.
If the idle does not go high at cold start and come down as the engine heats, replace the IAC.
The 401 code is a restriction as noted.
Remove the EGR and clean out the holes behind it into the intake manifold.
After reassembly put vacuum on the EGR with engine at idle.
The idle should get rough indicating the passage is open. The 401 should clear and not return unless there is some other issue in that path.
Good luck.

 

I cleaner iac and reset throttle to close as factory as I can with scnner .the bogging down is getting worse I am going to check fuel pump I hope that is the problem .any other suggestions would be great

 

Checking fuel pressure is ok but did the idle change with and without the connector on the IAC?
This is important.
Without the connector on the IAC, the idle rpm should be close to 550.
With the connector on, the IAC it should have raised to about 750.
Did this work out that way?
One item at a time.
Good luck.

 

Well I un plugged iac and set throttle like you said .I took the iac off just see if it was dirty abdbit did have build up on it so cleaned it with throttle body cleaner .installed it and keep it unplugged. Set the throttle back to factory when I plugged it in rpms did go up Alittle it is now around 650 . I still haven't checked feluel pressure I wanted this problem fixed first. Thanks for you help on that issue .now on to why it boggs down and losses power when I push the pedal down to go .after it runs for 15 mins

 

Ok, sounds good so far.
Check fuel pressure at the rail port near the fuel regulator with a gage.
It should be around 35 psi +/-.
Good luck.

 

How did this turn out?

 

Your codes 701 and 704; are you sure those are the correct codes?
Can't have a 704 with an automatic transmission.
The IAT is known on some trucks to cause excessive loss in power if it's too far to one end of it's range. It won't set a code but needs to be looked at with a Scanner when the truck is hot and power has perceived to drop to much.
Good luck.

 

Have you found out what is wrong with your truck? Mine is doing the same thing, I've put new wires, cap and plugs, checked fuel pressure is 34psi, new injectors, air filter. Looked for vacuum leaks and shorts. Nothing at all found. Where should I start?????Please and Thank you for any help.