Okay, had a lack of power since March. History of truck, 1999 xlt 4.2 bought June of 2015. Gott's mod, full exhaust with mangaflow hi flow cats and cherry bomb muffler all 2.5". Had upper end completely cleaned and new gaskets installed. Replaced #5 injector (dead), complete tune up (spark plugs, wires, coil pack, oil and coolant), changed all O2 sensors and got a trains flush all of the basics.

I still have a serious lack of power. I can floor it and it only drives like a grandma. Wondering where I should look. I have no codes at this time and everything sounds good. It is a little hard to start here and there but not excessively hard. Idles fine just seriously doesn't drive like it did last summer. Now I heard mad sensor could be an issue but don't know what else to look at other than ecm. Any words of advice would be good!

 

Any DTC's ? No CEL or MIL on ? Even if it's not illuminated, scan it anyway.

Main causes for lack in power are The EGR valve or plugged cats. Even if the cats are new, they are suspect.

 

Forgot to list that new egr and lines. Cleaned ports too. No cel or mil. I'll scan it when I get home.

 

Watching this thread kinda curiously now....

My 4.2 is SLOW on startup, when it hits around 2500RPM (guessing, I have no Tach) it wakes up and hauls butt. I figured it was just the fact of the dang true dual exhaust not providing enough back pressure. I have no cats, but my EGR system is intact, and pretty much what came on it 2007 when the engine was replaced by Ford.

 

Plugs can do it as well. Autolites are good for that since they are more less Motorcraft rejects. Bosch plugs heat up and fall apart inside the cylinder...very weak heat range. Yea they can be real picky when it comes to plugs. It's why only, -

Motorcraft
NGK
or Denso's

are recommended.

 

It doesn't matter as long as your still running all 4 converters. With the v8's you can get away with one, I'm not sure on the V6. No one will usually make those loud since they sound horrible when doing so.

 

Heh, the guy who owned this truck before me had true duals run. Basically chopped it off before the "Y" pipe and ran those together to TWO Flowmaster 40 series mufflers and then our to the back of the truck with 90 degree bends out the sides at the spare tire. It was.... Loud. So loud that it gave me headaches driving it. I went to a local muffler shop and they cut the flowmasters off, and put on 2016 Mustang GT stock mufflers with turn downs before the axle for me for like 60 bucks. I'm going to put it back stock with the pipe exiting before the pass. wheel. Not sure if I'm going to put cats back on it and go with a Borla kit, or just put it back as stock as I can. That Y pipe assembly is still expensive though.


EDIT: and I always use Motorcraft parts as much as I can. Plugs are Motorcraft

 

Guessing I got lucky, my combination with the magnaflows, cherry bomb and aftermarket headers it sounds like a mildly tuned v8 on the outside with a little bit of a v6 undertone. Still sounds like my 240 on the inside tho 😕 Oh well. At least she breathes

 

Well that's quite an accomplishment...hard to do.

 

Not bad, I think with the high flow cats, it reverbs the sound enough to make it sound good. Good job. Maybe I will go with a similar setup!