here is the deal. I got too used to my 4 cyl comanche. Now that i threw 33's on my stock geared 4.0 auto 99, it has WAY more power than my 5.38 geared 96 on 35's

something is not right here.

its a 96 4.0 aw4

the power only kicks in around 4250 rpms and even then it isn't too impressive. other than that it just kinda lugs along. I can still get it up to highway speeds no problem and cruise along just fine.

new parts:
plugs
wires
cap
rotor
cps
o2
air filter
fuel filter
alternator
battree

tps,iac,map are all good

cat is fairly new (could see through it when i put it in a month ago)

Hooked it up to the scanner and everything looks fine, no codes.

Not sure where to go from here.
any ideas?

 

maybe a clogged cat

 

put in a used cat i kept from one of my parts jeeps about a month ago could still see through it, didnt change a thing

 

maybe old cat plugged muffler?

was the honey comb on your last one all broke up? if so i would replace your muffler.

 

the muffler and tailpipe are newer than the cat

 

I would check fuel pressure like what was mentioned on Naxja. I'm sure its fine but when is the last time you checked the compression and leak down?

What brand of plugs? I have heard non champions can cause problems.

 

bosch platinums

never but if i cant figure anything out by this weekend im gonna go that route on monday

 

pull the rail with the injectors on... cut the key on... see if you got a bad injector... takes 10min and dont cost nothin... not sure if it would be the cause but worth tryin anyway... like a lawn mower... 2 much fuel bogs it down...

 

maybe your brakes are being held on slightly? just an idea... lol

 

did the actuation test with the scan tool, each checked out fine.

 

nope

 

bypass the fuel pump resistor

 

if that don't work unplug the TCU
if it is acting up it may be causing drag in the trany

 

now thats inginuity FTW! haha. sam i agree its more than likely a fuel pressure issue of some type seeing as you eliminated most things we would have told you to check first.

 

try running it with out a cat and muffler for a day just to see if it does any better and if it does then get new cats and mufflers if it dosnt slap the old ones back on.