I keep getting the P0121 code which I know is the TPS but my question is what is wrong with it? Also when I'm driving down the road and begin to slow down around 50mph down to 40mph it does alittle "bucking" and wanted to know if that was due to the TPS?

Last question is would putting a lower grade of fuel other than what your tuned for give you multiple misfires by chance?

 

Alot of people just clean the TB out and it seems to do the trick.

On the cable style TB there is an IAC valve that allows air to bypass and aid in controlling the idle. You can remove it and Clean the passage out then re install it. BE CAREFUL WITH THIS SENSOR IF YOU REMOVE IT!!! You can clean it but DO NOT MOVE IT IN AND OUT!!! YOU CAN DAMAGE IT!!!

Misfires can be caused by several things like the bucking you described.

Clean the TB first then reset the CEL and see what happens.
Start the engine up and let idle for about 10 minutes.

If it won't stay running Start it up and bring the RPM up to around 2000rpm for about 30 seconds using the gas peddle then slowly lower it to about 750 RPM and hold it for about 10 seconds. Then slow let all the way off. It will drop but it should relearn and compensate on its own within a few seconds. Then let idle on its own for 10 minutes.

 

Thanks for the help man

 

Ok I cleaned the TB and the IAC Valve and the IAC Valve wasn't out the 1 1/8" so while I was gone my buddy pulled it out the 1/8" it was short. Now when I start it she wants to idle around 1600-1800 and when I put aload on her she idles down to around 1000 but when I'm coming to a stop she doesn't want to go below 1000rpms.

So is there a crank relearn I have to do or something now cuz I'm lost?

 

Anybody??

 

You were not supposed to pull on the IAC valve. See Blown up red text above. An idle relearn could be performed but the only way I know how to do it is with the factory tool. You might try disconnecting the battery for 10 minutes then reconnect it, start the truck and just let it idle. IF YOU DISCONNECT THE POWER FROM THE BATTERY, DO IT ON THE GROUND SIDE!!! IF YOU DO IT ON THE POSITIVE YOU CAN DAMAGE THE COMPUTER!!!

Make sure you don't have a leak at the throttle body as well.

 

I can thank my dumba$$ buddy for jacking with the pintle while I was gone. I'll disconnect it in the morning cuz I don't think the neighbors would like me of I did it right now. Thanks for the help again man. I hope I don't have to replace the IAC Valve cuz the whole thing is $117 at autozone and $122 at o'reillys just for the motor.

 

It's most likely Just needs to recalibrate it self. Try that first

 

It had a code but didn't trip the SES light and it was P0507 (P)ending for the Idle being to high and what needs to be done to fix that or is it part of the recalibrate process.

 

P0507 is because the idle is high. The factory commanded idle speed is only like 575RPM unless it was modified in your tune for your mods. Either way the computer is detecting that the engine is running higher then what's being commanded. If it is not fixed, After 2 complete key on, engine running cycles it will set a permanent DTC and turn the check engine light on.

Any way try disconnecting the battery method I mentioned above and see if it will relearn.