Hello, I have a 1997 suburban k1500 5.7 vortec.
out of no where I am having trouble.
the idle will stay at 1100 rpm if I tap the gas pedal it will increase to 2500 and stay there till I shut it off.. then retard it may go back to 1500 or it will be 2500.
also this is having a huge impact on the transmission. It will go way above what it should in the rpms before up shift and then just the very slight difference in pressure on the pedal it will downshift and race the engine.
I have had the codes pulled 3 times.
first time it had the TPS mass air o2 ..
I changed the tps and cleared the codes.
truck drove less than a 1/4 mile before it started to lunge like I was flooring it.
I took it to a friend and used his scan tool and it pulled all the same codes as before
​​​he cleared them and left his scanner hooked up wile I went for a 15 mile drive.
it ran as if it was a brand new truck!
we then looked at all live data for all sensors and everything was within spec.
I drove it another 30 miles or so and then it started doing the exact same thing
I had the codes pulled one last time and again all the same stuff..
thought that I could have bought a bad tps so.. I replaced it again.. same issues. .
any one have any ideas? ? I am lost here

I should note that I did the lower intake gaskets 2 months ago.. haven't had any issues at all.. I have checked for vacuum leaks.. the previous owner had replaced the fuel injection system with the uprated injectors.
​​​​​​​this thing has been running like a champ till 2 days ago

 

And also its showing 20% thottle open while idle .. I have verified that the throttle plate is closed and that it works smooth

 

Right now, I'd suggest clean, and recheck electrical connections on the things you had issue with, MAF, TPS ect.

 

I know it's difficult to get an ohm meter on the connectors of the tps, but if you have one, go to ground with one lead, and to signal (I think it's the one on the side ), with ohms set, move the throttle the resistance should change. I believe you should have 0 resistance with it closed, and the resistance will increase as the throttle is moved open.

 

Yes I have also done that as well... I also removed the mass air flow sensor and cleaned it with the crc brand cleaner.. only thing I didn't mess with was the O2 sensors. . It has been code for those since I got it.. the cats was removed by the last guy and duel exaughst put on..

 

I can't find my volt meter.. think I loaned it and was never returned lol.. but I did check it with the scan tool and the voltage does go up as it should when I clear the codes.. it's 0.63 then increase to 4.05 at wot it also idles as it should around 650 rpm
​​​​​​​when it starts acting up it shows a 20% throttle position and goes to 1500rpm

 

If it's showing out of position, I'd go with replacing the TPS. The TPS is nothing more than a reostat sends battery voltage on both sides, and reads the signal from the wiper, that's what moves with throttle movement.

 

​​​​​​​have changed it twice.. thinking the first new one was a bad one..

 

I dunno, clean the throttle body, and remove the tps from the throttle shaft. Check the signal with it not connected to the throttle shaft.

 

I'll mess with it more tomorrow morning. . Gotta get to work in a little while.. besides it's 5 degrees out side here in ohio lol... but I will remove it and check it that way.. I was thinking that it is possible that the throttle shaft maybe messed up.. I'll remove it as welland check it ..
​​​​​​​a freind of mine says that maybe the ecm is junk since it ran good as new for a while yesterday before messing up again