Ok my 02 tahoe threw a P0420 code awhie back and you could feel it loose power and not rev good past a certain rpm so I hacked the converters off because it got so bad the back pressure would shut the engine down on the hwy if it got over 2500rpms. Well that fixed that problem but now it sorta feels the same way when it gets around 4k rpms. It will pull good until that spot then it feels like it has no more power to pull when it usually pulls the best around that rpm.

Could it be the fuel filter stoping up, maybe the muffler is clogged, maybe the tune on my truck is fudgin up? Im lost

 

did you retune after removing the cats? if not your tune will be off.

 

Post up more information man.

Whens the last time you changed your fuel filter? What kind of gas do you run in it?
How bout spark plugs? If so, what did you gap them to?

 

its a pcm4less tune and when I ordered it I had them to tune it for header and cat delete so I figure all they do is turn off the rear O2 sensors

 

I use 93 ever since I got the tune. The plugs are ac delco iridium somethin somethins but I forgot what the gap was but I checked them when put the in but its been a few months so I have forgot. It was awhile after I had those plugs before the po420 code.

I had this all typed up before and my friggin phone reset so I had t type it all over, got pissed an left some stuff out.

Im gonna change the fuel filter in the mornin since I did not have time before I went to work

 

if it was a fuel filter, or not enough fuel you'd get other symptons I'd imagine. knock, falling flat on it's face, etc etc. If they tuned you for a cat delete you wouldn't....eerrr SHOULDN'T get that code. They should of turned off all cat codes. How are you reading this cat effiency code? autoparts store? or you have a scanner? Have you reset? unplug battery for 5 minutes. Not a "real" answer, but may help if it is for some reason reducing power, I doubt it, but clear those codes (unplug battery for 5 minutes)

back to your original question, I am confused. You say cutting the cats off fixed it, but then it came back? or is it a different rpm problem?

 

Good luck changing that fuel filter. When I did mine it was a PITA cause u get gas all over.

 

I checked it at advance when it first kicked the code ten had them erase it. So it came back on so I checked it with a buddies obdII scanner and it said bank 1 catallist is below threashold (sp)

I wanted to make sure that was the problem since converters are not cheap lol so I sazawed em off and it fixed the problem (truck had no power above 2500rpms/shut truck down while driving)

So when I was on the way home I got on it and when it hit 4k it felt like the same problem as before but at a higher rpm but the truck does not shut off now thank god.

I figure the front O2 sensors threw the code since im (supposed) to have the rear ones turned off. I have only put about 25 miles on the tahoe in the past week so the code has not cme back on but I figure it could take up to 80-100 miles before it comes back if it even does.

 

Ok I changed the fuel filter (flex fuel filters are a PITA) Dissconnected the batt while I did this to reset the ecu. Well that did not fix the problem and while I was on my way to advance it started to stall out the same as before (2.5k rpms) and on the way home the check engine light kicked back on.

Im lost now unless the tune is goin bad somehow. So does anyone else have any ideas.

Oh and the problem gets worse the longer I drive it a one time, But if I let it sit for a few minutes the problem area is at a higher rpm like 4k then the longer the drive the worse it gets at lower rpms.

 

a tune can not change only mechanicals can change..how does it idle? does it smoke?