Car Starts then jumps to max rpm by itself

[RussW]

My '04 Aveo is an automatic that I've been working with for about a year now. It has been driving pretty stable until last week when it over heated and blew a gasket. I replaced the head gasket and put it back together without having any parts, nuts or bolts left over. When it initially cranked up, it sounded like it was running OK for about a second (smile on my face moment) before the engine RPM ramped up to 4 or 5K before I could shut it off. I looked at the throttle pedal, the cable, the throttle body, etc and tried it again. About half second after ignition, the RPM accelerated to its max and there is no movement at the throttle body, the throttle plate is in the closed position. I swapped out the IAC with a spare from the shelf and the same thing occurred. I swapped out the TPS with a spare and the same thing. Performed a visual inspection to make sure everything is plugged in, make sure there aren't any wires pinched under mounting bolts, inspect plug connectors for frayed or obvious wire problems. The intake manifold was never removed from the Head during the gasket replace so I'm ruling out intake to head gasket leaks. I looked for OBDII codes and nothing. I cannot keep it running long enough to get any live data on my meter. I disconnected the battery for a minute to reset the computer and started it again with the same result.

Has anybody here had any experience with the same or similar problem with an insight to where I might look next ?

[mazade]

The only thing I can contribute is that my '11 Aveo (Manual) seems to want to do the same thing, randomly, and the only way I got it to stop was to unplug the MAF connector.
...bear with me now...
I know the MAF is not the problem, as it is also NEW, along with a few other components, as you have performed...
I can't say for sure that this will work with your year, as I know that my Ecotec is a complete fly-by-wire setup and is dependent on every fart that the computer cares to contribute, so in my case I know that I've broken the closed-loop 'better performance and fuel economy' mode, but, at least it doesn't rev up to 4K+ RPM...
I do need to find the time to subject this thing to a real shop, and not my shade-tree attempts.

[RussW]

The only thing I can contribute is that my '11 Aveo (Manual) seems to want to do the same thing, randomly, and the only way I got it to stop was to unplug the MAF connector.
...bear with me now...
I know the MAF is not the problem, as it is also NEW, along with a few other components, as you have performed...
I can't say for sure that this will work with your year, as I know that my Ecotec is a complete fly-by-wire setup and is dependent on every fart that the computer cares to contribute, so in my case I know that I've broken the closed-loop 'better performance and fuel economy' mode, but, at least it doesn't rev up to 4K+ RPM...
I do need to find the time to subject this thing to a real shop, and not my shade-tree attempts.

My issue resolved when I unplugged the PCM (computer) and the MAF sensor as the same time and left these unplugged for several minutes. Plugged in the computer and cranked it up and it ran OK. No immediate max rpm event. I turned it off and reconnected the MAF sensor and started it again. Also, no immediate max rpm event. I drove it around the block a few times and it ran ok. I did have to clear the MAF code that was set when I first cranked it up but I haven't seen it since. Runs as good as expected for an Aveo. Thanks for your reply and hopefully our comments here can help someone else.