I had to replace my top end and went with a diff grind cam, after the rebuild I get a 121 tps code, and it causes the car to run like crap, and I also notice the TCS off light comes on alot and sometimes the car runs fine and it seems to do it when the light is on.

Ive also noticed my LOW TRACTION light comes on and stays on at speeds above 70mph.

any thoughts on this? I have replaced the TPS sensor 3 times so its not that. grounds seem to be ok.

I do have header gasket leaks but I dont think that would cause it.

any ideas?

 

Maybe a loose ground on the back of the head?

Or loose battery.

Header leak wont cause that issue, but needs to be fixed for closed loop stuff to perform correctly.

As for the code, It is usually set because the rpm vs tps is out of range, In EFIlive go to table C3907 and maybe lower the values a bit more?

Also a large vacuum leak could cause this issue as well.

 

hmm il have to look into the vacume leak, and the grounds look pretty tight on the back of the head those are the only ones i took off, so maybe the tune is a little off wit hthe c3907 possibly also. thanks for the input 3 very good places to look.

 

http://www.hptuners.com/forum/showthread.php?p=101510

That was my fix in hp tuners. My car would drive fine but would shift below 5500 at WOT. Then on top of that randomly the car would start to idle low and surge, my afr's were in the 12's while idling. All was fixed with the above. I had also replaced my tps and it did nothing.

Good luck buddy!

 

Did you change throttle bodies? There are tables in the tune that determine the voltage to set a TPS code and sometimes when the throttle body has been changed the TPS sensor needs to be set properly for everything to work. Check the voltage from the TPS sensor closed and wide open. This will narrow down what the issue is. It's also possible those voltage parameters I was talking about got set wrong in the tune.

 

no did not change tb only i switched to a fast 102 and a cam and had a valve job done on the heads

 

Im thinking these guys hit it on the head with the tuning issue, funny thing is it comes and goes, and car seems to run better when the TCS OFF light is on, and the low trac light started comming on to and before the swap there were none of these issues. the cams were not all that different in size though but maybe its off just enouph to cause it. I am going to fix the header leaks and double check some things and get it back to the tuner next month.

 

So you already had a big throttle body on it before you swapped this stuff or you changed throttle bodies with the intake and all at once? Basically what I'm trying to find out is if the throttle body was changed it may cause the TPS to go past it's boundary. Usually bump stops or TPS adjustment has to be adjusted with alot of these aftermarket throttle bodies.

 

I used the same throttle body I fast 92 I took it off the stock ls3 and put it on the fast 102, the throttle cable bracket was changed back to a standerd ls1 style from the custom one that was on the ls3 intake. I re adjusted the cable to get it to the right tightness

 

Ah gotcha, check your voltage on the TPS like I said and then have your tune tweaked for the MAP sensor test faults shown in that thread above.