2004 Chevy Venture Accelerates On It’s Own

I have a 2004 Chevy venture van with a 3.4 that accelerates when it wants to. It happens when cold or hot, just starting or going down the road. I have changed the TPS and IAC and plugs for both of them. Found a bad vacuum line between Map and fuel pressure regulator and also one on the EGR and replaced both of them. I removed the throttle body and cleaned it. Not finding much on the scanner. Short term fuel trim is at 0 and long term is at -5.

Alright, usually a problem like this is caused by a bad throttle position sensor. Did you replace it with a GM part, or aftermarket part?

I replaced both with OEM parts from dealer.

Can you watch the voltage of the TPS on the scanner as you move the throttle?

Yes. It is good. Also my sister stated that recently when she started it a couple of times the valves were rattling very bad and then settled down

That probably doesn’t really concern the unwanted acceleration, but it is something that should be addressed. Usually lifters on those engines, unless you’ve got a rocker or two that have come loose. As for the acceleration problem, you seem to have covered most everything that usually goes bad. I would check the wiring from the TPS to the computer and look for any corrosion or shorts. If the wiring checks OK, you will need to replace the computer.

I will go through the wires and connections again. I was hoping for something other than the computer. Thank you

Yes I understand, it’s really the last in line of components, but I have replaced them before to correct that problem.

OK, thank you very much.