I have had my 2004 since it was new and recently I have had a power loss problem from 0-40 mph. I have taken it to 3 shops and they have tried everything to figure out why I have this problem, I was told that the coils needed to be replaced and that did nothing, I have changed the fuel filter external to the tank, replaced the catalytic converters because I was told they were plugged up, the 02 sensor was replaced and all of this has not helped so I took it to the Ford dealer and they could not find the problem either. The problem worsens with higher temperatures outside...I live in Arizona. Can anyone think of something that nobody has thought of please? I love my truck but I am getting real tired of chasing my tail.

 

@tommkrause


I experienced exactly the same symptoms you mention and did all the same things you mentioned, including suspecting barometric pressure sensor readings and intake air temp. (I Even replaced the MAF sensor which incorporates IAT, although more for attacking the Random Misfire symptom I was also suffering). Nothing really made dramatic difference in power.


However, at 212,000 I did a major timing chain / Phaser job, and I can NOW report two things relating to your post. A major difference occurred immediately upon completing my timing job - which included lots of other components, but none of which one would expect could effect power (ie, lifters, roller/followers, spark plugs, all 8 fuel injectors, etc). I'm of the opinion degradation of valve timing has a significant effect on power - if your engine has upwards toward 150-200k on it.


Secondly, over the next two oil change periods (6,500 + miles) after my timing job, I have witnessed a noticeable gradual increase in accelerator responsiveness and power. Like an unexpected / unexplained 'break in period'. Specifically, there is a long gradual grade I frequently traverse that it will now climb without shifting down from OD. That's like when it was new. It seems the PCM may adjust some parameters of a very long period of time.

 

Thank you so much for the tip, I will pass that along to my mechanic and see what he thinks. I only have 111,000 on the truck but I will try anything at this time.

 

It would be helpful if you could provide a better description of your problem - "power loss" is vague.

Do you get a CEL? Are there any pending codes? Does it feel like a misfire? Does it feel like you push the gas pedal but there is no response from the engine?

Do you have a OBD tool like Ultragage so that you can see codes, timing, ECT, IAT, fuel trims, throttle position, ...?

When the engine coolant temperature (ECT) or intake air temp (IAT) gets too high, the computer will decrease timing and go into a safe mode.

You have already thrown a lot of unnecessary parts at it. Did the mechanic feel the problem when they drove it? Don't let a mechanic attempt to fix a problem unless they have experienced it.

I have the shop manual and am willing to help but we need to better diagnose the problem.

 

The problem is when I go to take off from a light I put the pedal almost to the floor and I have trouble keeping up with a bicycle but when I get up to 40-45 mph the truck runs pretty normal, also when I put my foot to the floor it acts like it is missing very badly....bucking and chugging. The problem is the worst when the temp outside is over 90 and seems to be a lot better in the mornings and night when it is cooler. My mechanics have felt the problem and the dealer did too but nobody has a clue why it is doing it because there are no codes. Last week I was driving the truck and it started really bucking and almost no power and the check engine light came on momentarily and then went off, I had my mechanic check the code and it was cylinder 7 misfire and that was the first real code I have had, after the mechanic cleared the code the truck has been running the same as it was before the code came on. I had one mechanic say that the number 2 cylinder had some weird readings on his screen, it was -2 and when he put the truck in gear and power braked it and raised the engine it went up to 0 when all the other cylinders were reading something completely different. I don't know how to tell you any better than that what it is doing. If you have any questions let me know.

 

How fresh are the plugs? What type? Were the boots changed?
With a cold engine I would wet all the coils with water and then drive, trying to throw some codes.
Search on "misfire". Could also be a timing/VVT issue.

 

@tommkrause
Having re-read your posts here, I think @Ted928 is very correct. I originally assumed you were 'simply' experiencing what he pointed out is quiet a vague symptom - "loss of power".


You haven't indicated in your profile or by post which engine we are dealing with. I now notice you have much different symptoms that RESULT in a loss of power complaint very common with the 5.4L Triton. I also note you have not mentioned changing plugs, and on the 2004 - 2007, THAT is a big enough issue you probably would have remembered to mentioned it. These engines will easily go more than 100,000 miles on a set of plugs. Although it is NOT smart, but lots (including myself) have done just that, all the while complaining about "random misfires" and "bucking". Then after changing plugs and COPS still complain about the same issue. You might search on those two quoted terms. Perhaps you could get some help by reviewing my theory on the subject of random misfires and the broken spark plug issue on these engines posted here:
5.4L 3V Spark Plugs Engine Build Dates before 10/09/07 - Page 86 - Ford F150 Forum - Community of Ford Truck Fans


Help us help you narrow things down.

 

I had the plugs and coils replaced last week because my mechanic thought the coils were bad and it made no difference, I used autolite plugs and this is for the 5.4 Triton motor. I had the plugs replaced at 75,000 amd I have 111,000 on it and the reason I replaced them again was because one of the mechanics I used in the past did not tighten the number 6 plug so when I took it to the dealer they asked me to have the mechanic that put the plugs in, remove them and put them back and tighten them correctly, I had the plugs removed and bought some new ones being they all had to be removed.

 

I am having trouble understanding what you are saying. I think you are saying:

You had the plugs changed at 111,000 miles.
You previously had the plugs changed at 75,000 miles.
Somehow someone discovered that the #6 plug was not installed properly.

Since you are having a misfire issue, your problem might be related to spark plugs. There have been issues after installing new plugs.

 

I tried to give as much information that I have. I replaced the plugs as regular maintenance at 75,000, when I took it to the Ford dealer because of the problem I am having with the loss of power, they told me that the plugs were loose so I took it back to the mechanic that did the plugs at 75,000 and had them pull the plugs and install new ones at 111,000 miles. The misfire problem started long after the plugs were installed at 75,000 miles but when I had the plugs replaced last week at 111,000 miles I had a #7 misfire but it went away and I have not had any misfires since, that was about a week ago. I replaced all 8 coils at the same time I did the plugs last week because the mechanic said that they might be the problem but it did not cure anything. The whole problem lies with loss of power from 0-40 mph, I am not getting any codes right now but I still have no power. The Ford dealer re-programmed the computer because they said it was not up to date. Since this is the second set of plugs in 36,000 miles and I still have the same issue, I don't think it is spark plug related, this is something that has baffled everyone including the Ford dealer. I am trying to get some fresh thoughts so maybe I can get the problem fixed before I have to get rid of the truck which I do not want to do.

 

Are you sure that the mechanic actually installed the new plugs or maybe he just tightened????

You have said that all is fine when the engine is cold. Try the water test I mentioned to see if you can create the problem on a cold engine.

 

Yes the plugs are new, the mechanic kept the old one and showed me them and the #6 plug was only hand tight and had all kinds of blow by on in from being so loose. The problem does not exist when the outside temperature is less than 90 degrees, the truck runs great when the weather is 80 degrees or less. This is a outside temperature problem. If it was a boot getting wet, it would not run correctly only if there is water around it. I DO not think the problem has anything to do with the spark plugs and it has been proven by replacing them and having the same problem, this is something out of the ordinary that is baffling everybody.

 

Be careful. Like something that is lost, we don't know WHERE it is. Here it's my understanding we don't know WHAT it is. I do note you have said "also when I put my foot to the floor it acts like it is missing very badly....bucking and chugging." You will find many around here that do not like Autolite plugs very much, and may find it hard to discount plugs or certain aftermarket coils.


At this point, I don't have many good suggestions - seems to me the situation calls for some technical diagnostic data - like from a good scanner capable of giving you live readings from sensors and various readings that are available from the PCM. Only thing I can offer is the attached set of Diagnostic Reference data for the 5.4L 3v from my documentation. Perhaps you can find a reading out of whack somewhere without a scanner, but many of the reference values come from PID readings from the PCM.


Maybe this will help isolate a direction to look.

 

The PDF files probably mean something to a mechanic but nothing to me, I guess I can print it off and give it to the mechanic. I am and engineer by trade but not in automotive. Thank you for the input. I am assuming that I should have used Motorcraft plugs?? I had another mechanic say he did not like the Autolite plugs either. I really do think that the problem has something to do with the outside temperature because it is running perfect right now. Is there something that happens to the motor or computer to compensate for the temperature?? I am asking this because I do not know, and is it possible that the compensation that is happening could be the cause?

 

I did not say your problem is because of a wet boot. You understand very little.
The test is to determine if your ignition system is prone to shorting. Perhaps due to a defective plug (which I have had), or due to reusing boots on a different brand plug which has a different insulator shape (which others have had).

The main temperature sensors are IAT and ECT. The computer makes small corrections when needed (decreasing ignition timing) but that does not cause the engine to buck; just a small decrease in power.
The computer is very good at determining if a sensor has failed because it knows what signal to expect and failed sensor usually send a very wrong signal.

Determining a misfire is difficult because there is no misfire sensor. It looks for too small of an increase in instantaneous engine speed at every spark event to deduce if sufficient power was not made on that spark event. Meanwhile, the purpose of the flywheel is to smooth everything out, minimizing those pulses - so it is hard for the computer to notice. Repeated misfire is necessary before the computer has confidence. I had to get massive misfiring thanks to the water test before it threw a code.
But since you are sure your problem is not due to the ignition system, perhaps you need a new computer.

Please let us know when you eventually solve the problem as it benefits the community.