2004 FX4 power loss
 

I have a 2004 FX4 with a 5.4. I just had the engine replaced for the second time in 2 years and it does not have any power after 2500 RPMs. It will not pull my camper. It does not have any codes, it is not misfiring at all. Just after 2500 RPMs it does not gain speed or power like it should. Does anyone have any ideas were to look. I have removed the CATs, changed the battery, changed the fuel filter, still nothing. the first engine with the cam chain hitting the cover had more top end power than this thing. HELP:help:

"Does not gain speed or power like it should" makes it seem like a tranny issue to me.

Having gone through 2 engines you should have gone through a trans too.

Tranny has been replaced about 10,000 miles ago, before engine problems. Talked to him because someone mentioned the torque converter. It is shifting fine, just around 2500 to 3000 RPMs, the way it gains is not as fast. It feels like it is not getting enough fuel or air, but the intake is clear. Stepping on it right from the start it cherps the tire and then falls off around 2500 like I said. Pulling my camper it won't go over 40 MPH.

Has the FPDM been checked or replaced. The FPDM controls fuel pump output pressure.
Check it to see if it has corrosion or is cracked.

Have you gone back to whoever rebuilt or replaced the engine? They should have some responsibility.

Yes I have called them. Funny you asked about the FPDM. Looked at it today. Was really corroded. I took it off and cleaned it up and noticed a crack on the back. Could that be what is doing this? The truck has sat quite a while for the engine problem. But it has no code at all. Could the FPDM still be the issue? The company I bought the engine from, Powertrain Products say check fuel delivery.

With corrosion and a crack on it, who knows what the electronics are doing?
Need to replace it whether or not it may be part of the issue.
Get one from Amazon for under $60:
https://www.amazon.com/Dorman-590-00...&keywords=fpdm


Before and or after the FPDM, check the fuel pressure at idle and when power drops off.

I will get back to you on it and see if that works.

OK, so I changed the FPDM. Still hits 2500 RPMS and no power. Noticed today driving it, that it will not go over 4000 RPMS. Then it has a slight vibration when it gets to 4000 RPMS. Any more Ideas, cause I am at a loss and this thing is killing me.

***gt Pool,

Sorry your experience with the 5.4 has been less than acceptable. You say it will 'chirp' the tires from a start but struggles above 2500 R's - that's where My 2004 5.4L (with 220k miles on her) really packs you back in the seat and comes on. It will scat wind up and shifting between 5200-5400.


I think you may need some live scanner data to properly diagnose some areas to concentrate. Suggestions you have gotten so far are good. I can suggest a couple of other "Subtle" things I have learned by monitoring live data from sensors on my 2004.


One possibility might be Knock Sensors, located underneath the IM. They are basically little microphones mounted to the block on both banks. VIA them, if the PCM senses labor knock - it reacts by reducing Spark Advance. That can dramatically effect power. The PCM gradually recovers advance (OVER what timeframe IDK). But the PCM constantly monitors (those "microphones") for Knock. Any constant source of noise could confuse them. I had to replace a NOISY A/C Compressor - and was very surprised to note the Knock Sensor on Bank 1 read noticeably lower voltage level afterwards - It could 'HEAR' that noisy A/C Comp. And I noticed a marked improvement in accelerator responsiveness. If you have 'spurious' noise (A/C Compressor or idler pulley or ticking lifters), it could have negative impact on power. Knock(s) do not produce a DTC, although the sensors are monitored for 'electrical integrity', so I do not suspect failure of either sensor.


Another possibility might be the IMRC (swirl control) valve. You practically have to use a borescope or USB camera & laptop to observe / verify it. The 5.4L IMRC valve operates 'butterflies' (similar to throttle body butterfly) in EACH intake port of the intake manifold, right below the injectors. They should close at low MAF volume air flow to improve fuel atomization in slow moving intake air. They must begin to open between 2000 - 3000 RPM depending on air temperature, engine temp and some other UNK factors. BUT - I can Monitor live data from my IMRC valve, and FEEL the torque and power increase when they open. If they are stuck closed or inoperative, that would cause your symptom. However - you should get a trouble code --- if that is it.

Another possibility might be one of the various temperature sensors producing FALSE readings. The PCM Logic will reduce POWER in response to elevated ECT, CHT, or OIL Temperature (and perhaps others) in an valiant effort to protect the engine - well before a DTC is set. Recently, I read about PCM logic reducing power if it senses elevated Oil Temperature to keep from breaking down the oil, thus possibly damaging the engine. IDK, but almost certainly - that logic might adjust valve timing TOO in order to reduce power - intentionally. Verifying outputs from those sensors would require a live data scanner, but are ideas that might help you out.


Just some thoughts that might help.
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P.S. Thank you for your 20 yrs service in the Marines for us.

Thank you for the info. I am beginning to think that the shop who put it in forgot to hook some sensor up, which there are so many. Where can I find one of these live scanners? I get the feeling it is the IMCR but, without checking it I don't want to pull the manifold to find out. Your very welcome on the 20 years. It was a fun time for me.