Does the 5.9 have an IAC? Might be faulty as well.

 

My bet is plenum. You can check this by removing the breather, opening the throttle plate and peering down with a flashlight. Any signs of oil and the plenum gasket is hosed. Common issue. Recommended fix - Hughes plenum kit and you'll never have the problem again...

 

Yes it does

 

Won't go over 2000 rpm?

Clogged cat. But replace your plenum with the ebay aluminum plenum plate.
Then get you a new cat and NTK 02 sensors, that, in theory, should fix your problem.

 

so it wasnt the cat.... replaced the O2 sensor ofter the cat... no change... now its throwing codes P 0031 and 37 also P1296 ... And I've already changed the TBS. again when I put it on the computer last time it said my O2's were fine... and I've already tried resetting the PCM .... I'm pretty sure my plume in ok .. didnt look that bad from the top end..... I no its something stupid .... ???

 

I think it is time to let the dealer look at it... throwing parts at it isn't getting you anywhere.... :-/

 

P0031 means:HO2S heater control circuit low (Bank 1 Sensor 1)
I couldn't find 37...but it also has to do with the 02 sensor heater.

P1296- No 5 volts to MAP Sensor Loss of a 5 volt feed to the MAP sensor has been detected.


And the 02 after the cat doesn't really **** off the PCM unless it just fails. It's the pre-cat 02 that is messed up. If you haven't already, replace that guy with a Denso or NTK.

 

NGK*

Replace the Upstream O2 Sensors, and also might as well replace the MAP sensor too...

If that all doesn't work then you've got something crazy going on!

 

No, not NGK, NTK.
They're made BY NGK.
Same thing.

 

Thank you all for all your help..... will deff let ya no what happens .....