Thread: 99' GTP Struggles under hard acceleration?

Today my car started acting up again like it use to (Stalling when coming to a stop) so I started going through my list of sensors to look over for and got to my IAC sensor so I took it off and it was filthy. I mean caked with carbon. So I cleaned it up and put it back on and drove the car and I no longer had issues with it stalling. HOWEVER on my way to my brothers house I noticed it would shift into overdrive and then shift back down then shift back up, then back down. Finally I just shifted down into 3 and it stopped. So I had to get on the freeway and gave the car about 80% throttle and the SC started to boost up and then immediately started to feel like I was getting a bunch of lag. Just kept shuddering and trying to shift up then shift down.
The transmission is fairly new I had it installed about 3 weeks ago so I know thats not my issue. Could it have to do with carbon buildup in my throttle body? I sprayed throttle body cleaner in it couple weeks ago when it was doing the same thing and the issue stopped but now it is back.
I'm at a complete loss.

I'm at wit ends with this car seriously. Today my CEL came back on for the TPS (low imput), I've replaced the sensor, cleaned the throttle body, replaced a cracked hose, cleaned the IAC and STILL have issues. The car today didn't want to shift into 2nd only when I floored the accelerator did it shift, then when coming to and intersection I let off the throttle and the rpms dropped drastically to the point where it almost stalled. I am serious at a dead end. Someone please help me before I go out there and drive it till the motor blows up

I don't see where you said you had it scanned for trans codes. I would get this done and see what comes back. If the engine is running correctly then it sounds like you may have a trans issue, as when you say it almost wants to stall when coming to a stop makes me think there is an issue w/ the toeque converter not unlocking.

And no, a trans. code will NOT show up as a CEL on your dash. You will need to find a trans. shop for this one as a normal Autozone scanner won't read these codes.

Then why would a p0122 code come up?

The P0122 is an engine code, but a trans. code will not turn on the CEL light. It is stored in the ECU and read by higher end scanners. Usually the autozone scanners cannot read ABS or trans. codes. A GM TechII can.

Well I just had this transmission installed about 3 weeks ago, there should be no reason something has gone faulty on it. I dunno.
I replaced the TPS sensor last night and the issue went away but my car kept a steady idle at 2k rpm in P but in D kept a steady idle at 1100rpm. Car shifts fine and doesn't stall now though

Take it to where you had the transmission installed and see if they will look at it for you. I know at my shop we check it out to make sure it has nothing to do with our repair. We let the customer know if it is NOT related they could be charged the regular diag fee, but if it is related to the repair performed it is covered under waranty.