Poor power and milage
 

2005 4.7L V8 QC 4X4 Auto (545RFE) 107K

So over the past few months the Dak has been putting out less and less power and the mileage has been going down way low as well. How low? Well I can't give exact numbers on the power but it is to the point where I use tow/haul mode regularly because the extra mechanical advantage has become a necessity. The mileage has dropped from 15/21 down to 11/14. Aside from an exhaust cutoff which I did AFTER the mileage and power went to s***, the truck is bone-stock as far as drive train goes.

I had a friend do a fuel trim test with the truck idling and nothing was off so no luck there.

A month ago I ran a test drive to confirm the milage at 11/14, then sprayed seafoam cleaner down the throttle body and changed the PCV valve (my master technician neighbor advised it but I don't remember why). I ran the mileage test again and noticed the power was up and the mileage was at 15/21. However the next day I poured in seafoam before doing a hot oil change. After that I retested the mileage and power and it went back to s***. Also the new PCV valve vibrated badly but has since quieted down. I don't know if the mileage going up or down was coincidence or what but it happened regardless.

All my life I've had to fight to keep engines running so when it comes to keeping an engine running well I'm lost. I'll list out a few things I can think of but feel free to ask.

The air filter is about a year old and is still clean. The spark plugs are platinums that I got about a year and a half ago. There is a really annoying ticking valve the goes away after about 60 seconds. The previous owner didn't keep up with any maintenance as far as I know so if there was something that should have been replaced within the past 70k miles I probably need to look at it.

Any help is appreciated.

TL;DR The engine is running like s***. I need a list of things to look at.

Change out the platinums for standard copper core. These engines hate platinums. Thats where I'd start.

I've read that before but I thought since it was around 6 months after the new plugs that the power started going down that the plugs were fine. Would there be that long of a delay?

If the engine is running like ****, that needs to be corrected and is probably the source of the bad economy.

Are you referring to the ticking valve? It has been there all along and I've actually made it better throughout the whole issue with the engine.

Could also be an exhaust issue ie stopped up cats or muffler, get copper plugs in there, and also check the galvin units at a shop to make sure u are getting proper intake flow

This is from another thread near yours and so true. My commute at one time was up to 34 miles with about 10 stops and average speed of about 45. I was getting 17-19 mpg. Now my typical drive is 8.5 miles with about the same amount of stops......mileage is 12-13 now.

Have you tried running better fuel? My Dakota is really fussy with gasoline brands. Basically, it spits and sputters when filling up at almost every station and mileage suffers. I have 3 go-to Shell stations and every time the truck runs perfectly with good mileage.

Besides, these 4.7's and so many other Dodge engines are well known to drink fuel. +1 on getting those copper core plugs back in. I made the platinum mistake once before. It's worth it even though mine have to be changed at 25k. In most cases, it's best to stick with the plug the manufacturer built the vehicle with.

The 11/14 was 11 doing the daily stop and go and the 14 was resetting the economy calculator and cruising at 65 for 11 miles of interstate and just an attempt at giving a number to show just how poor the power is. Honestly I don't care if the mileage is bad I just want the power back. I kills me every time I put the pedal down and know I just wasted a bunch of money on gas and am not even getting the power I got a year ago.

I have tried different octane fuels and had essential the same fuel economy. No ethanol free since there isn't any near me.

I know other 4.7 Daks get worse mileage but that's not a reason to accept the recent drops.

OK so I'll get the coppers and then go from there. Next time I'm home I'll talk to my neighbor about the intake and cats. Should I go ahead and replace the coils or are they a work/not work component?

The coils are typically a work/don't work type of thing. I wouldn't do anything with them myself.

Use the least ethanol possible if that is an option. 87 or 89 octane at most, no reason to go any higher unless you buy a programmer, like the SCT or Superchips, which can program your engine to take advantage of higher octane.

+1 for changing the plugs. The only 4.7 designed to use platinums is the 2008+ revamped 4.7, and even then only for the lower bank (2008+ 4.7s use 16 spark plugs like the larger Hemi engines).

Mine isn't as fussy about gas stations, but definitely stick to good name brand stations.

Does it coast easy? I had my calipers stick before on another vehicle, but it was kind of obvious when i'd let off the pedal and it'd slow quickly. Gave me the same symptoms of low power/economy.