04 Aveo with uncontrolled RPMS on start up

[rocky49]

Car is an 04 Aveo with a 5 speed transmission no air conditioning. We have 3 aveos, this is the White Zombie Aveo. Ok list members I did the head rebuild after a timing belt tensioner blew up at 90,000 km. This is the second engine in this 04 Aveo. It came out of an 05 Wave. It was year long task. Someone else started it and never got around to finishing the job. I finally got at the job in late August. All 16 valves were bent even though the engine failed on start up. The intake and exhaust manifolds were sitting in box for 10 months collecting dust and grime. I finally got the car back together yesterday afternoon and fired it up and the RPMS just keep going up and up. Only control is turning the engine off at 5000 to 6000 RPMS. Pretty exciting stuff as I don't think I have ever got this kind of rpms out of the car. This is simply a blast of uncontrolled engine rpms on start up. This is without my foot on the gas pedal. The car was a write off once upon a time so I can't tell if GM ever did the throttle body mod on this engine. I manually disconnected the throttle cable and that had no difference, the out of control acceleration continued. The front passenger wheel was off and on jack stands so I did not engage the clutch to see if I could get control. I then took the throttle body off and cleaned it up with carb and choke cleaner and now it does not want to start at all. Any suggestions on what is going on with the White Zombie Aveo?. I have taken one of the sensors out of the throttle body and cleaned it up as it and the throttle body with carb cleaner. The sensor was covered in carbon. It was the one with 4 pins and a cylinder shaped sensor. I could not figure out how to get the other one loose (I think that one is a throttle position sensor but I am not sure) . I do have a code reader and will try and get codes today. Thanks to the member who posted the change the timing belt sequence with photos on the forum. Please respond to the forum or directly to tya2@4-fly.net Rocky49

[avguy]

Maybe the TPS, connector, or wiring was already bad, and in trying to remove it you finished it off. IIRC, removing the TPS wasn't a real big deal for me, even though I didn't have the TB out. What specifically was giving you a problem trying to remove it? I don't have any specs to test the TPS - you probably need a FSM for that. Or you could just take the easy route and try a new one, assuming that you don't see any problems with the connector and/or wiring. I guess it could also possibly be a bad IAC as well, but it sounds more like a bad TPS.

[rocky49]

There were no codes when I checked this morning but the battery was off for 10 hours while I recharged it. The problem with removing the TPS se.nsor if that is the name of the other sensor on the cable driven 04-05 throttle body is that the heads of the fasteners are F*()_D up. I thought maybe I could get it going this morning but no such luck. Off to pick your part to see if I can find another AVEO with a throttle body. I hate that this forum refuses the opportunity to add sentence and or paragraph breaks. Rocky 49

[avguy]

Did you try drilling and using an EZ-Out? Maybe even just a left-hand drill bit alone might work with those small ones.

The left most button (Source Mode) will let you do skips and paragraphs.

[rocky49]

The other day I posted about high revinng 2004 Aveo after doing a head rebuild. Further information. First we swapped throttle bodies, problem is still there. Then we swapped air inlet hoses problem is still there. Then we tried starting it with the throttle cable disconnected from throttle body (only goes to 4500 RPM maximum instead of 7000+ and climbing, Next we tried unhooking the physical connectors for the two plug on the throttle body, still not change.

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TO SUMMARIZE WHEN STARTING CAR GOES TO IMMEDIATE WIDE OPEN POWER WITHOUT HESISTATION AND THE ONLY WAY TO TAME IT, IS TO TURN IT OFF. IF THROTTLE CABLE IS PHYSICALLY DISCONNECTED IT WILL IMMEDIATELY GO TO 4500 AND STAY THERE.

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I WENT TO THE GM DEALER AND WAS GIVEN THE THROTTLE/IDLE LEARN INSTRUCTIONS. We tried them 3 times without any effect. What next?

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I can not believe GM would allow a car to have an engine design wher something fails and the engine goes to wide open throttle.

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Please help Thanks \Rocky

[avguy]

Seems that this is looking like a bad ECM, unless TPS wires have crossed over. One easy thing to do is test the pins of the TPS connector with the key in the on position. The outside pins should be 0 and 5V, and the middle should be 0 as well. If the middle is around 5V that would explain most of this, except for 4500 RPM with the throttle cable disconnected. That part just doesn't make any sense at all. If the TPS connector voltage on the middle pin is bad, check for a crossed wire. Otherwise it would seem like the only thing left is either a bad ECM or perhaps an AVEO/WAVE or '04/'05 ECM mismatch.

[rocky49]

Seems that this is looking like a bad ECM, unless TPS wires have crossed over. One easy thing to do is test the pins of the TPS connector with the key in the on position. The outside pins should be 0 and 5V, and the middle should be 0 as well. If the middle is around 5V that would explain most of this, except for 4500 RPM with the throttle cable disconnected. That part just doesn't make any sense at all. If the TPS connector voltage on the middle pin is bad, check for a crossed wire. Otherwise it would seem like the only thing left is either a bad ECM or perhaps an AVEO/WAVE or '04/'05 ECM mismatch.

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OK I will check these voltages later this morning. I am pretty sure this is the original ECM and it has been in the car for 190,000 km (about 120,000 miles). When I run a diagnostic it comes up with the right VIN for the vehicle. Since the vehicle never physically left garage with the recent head work and all I am pretty sure it has not been swapped out. What is the story on ECMS for Aveos. Will any earlier model AVEO /Wave ECN from the same configuration work? Basically we are talking the base hatchback, with 5 Speed, no air or cruise. The only real mode to the car was swapping out the radiator for a larger one after an accident because that one came with the front clip, and installing the wave engine at 100,000 KM when the original Aveo engine blew a timing belt. And this is why it is called the white Zombie Aveo, it refuses to die, and we refuse to let it die.... Rocky