Car is trouble. No clue what to do anymore

everydaycarguy

I have quite a bit of money in just simple wear and tear items on the car like clutch, slave and master cyilinder , altinator, fuel filter oil filter all liquids, spark plugs, coil pack, throttle body(cheap one from a friends car that ran fine just was ripping it apart),starter. Fuel pump. But so now the car is stuck on engine power reduced mode and will not go above 3k rpms in and gear of the 5 and won't go above 30ish mph. I have been told computer maybe. But I'm just clueless and would like some sort of idea before o put any more money into it.

stever

What kind of Chevy? Year? Miles?

Have to tried to see if it's throwing any codes?

everydaycarguy

Chevy cobalt ls 2006 154,000 , throws throttle actuator code but that why I got new throttle body but still nothing.

Mr_Shiftright

What's the code # exactly?

everydaycarguy

P0121,believe that what you looking for

thecardoc3

P0121 is "airflow rate calculated to be greater than expected". Is the vehicle software at the most current level, and did you use a Tech II to perform an idle relearn when you replaced the throttle body?

Mr_Shiftright

Probably the best way to trace this problem is to use an oscilliscope.

Here's a DIAGNOSTIC TREE for tracking down this problem.

Basically, you either have a bad TPS, bad/corroded wiring, no reference voltage to the TPS, a short to 12V (should be 5V) or a bad ECM.

thecardoc3

I looked at that reference you linked. There are some cars that it is accurate, and there are quite a few that it isn't. Even in just the Cobalt (2006) with the different engines that are available there are subtle differences in the code descriptions and code enable criteria. For example the 2.2 Ecotech is primarily just that the airflow measured is too great for the throttle opening reported. A fault with the MAP sensor or its signal could cause the computer to generate this code, or even some type of fault that would have the manifold pressure be higher than it should be for a given throttle position fits the description of the code. With the 2.4l, the P0121 is paired with P0068. While the description is still that the airflow is too high for the throttle opening reported without a specific throttle body or throttle position sensor code also setting the diagnostics have the tech concentrating on MAF and MAP sensor signal inputs first.