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    Thread: Hesitation in acceleration, jerky cruising

    1. #1
      What's wrong with my car?
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      Hesitation in acceleration, jerky cruising

      Hi,
      I have an 2008 Aveo Hatchback Special Value model with 36,000 miles on it, and paralleled to my peers, had similar issues with acceleration and cruising. What I experienced was a hesitation once stepping on the throttle after a second or two the car would in explicitly gain power and get the acceleration and then out of no where would loose all that juice. It happened all the time and with a manual, first gear really seemed to amplify this problem so much so, I had a burning desire to end the car's misery with a couple of shot gun shells. Constantly stuck in Tampa traffic, it seemed that there was something amiss and with no check engine light ever coming on it seemed that it was a figure of my imagination. So one day I decided to hook up my ODBII meter to the car and get the figures from the car as it was running. Many readers will give you a real time report of the sensors as the car is running. I decided to do my 20 mile round trip to work and back and want to report what I have learned from the analysis. It seems that the check engine light will not turn on until one of the sensors report a significant error such as 0V or no signal back to the control unit. However, my car was showing something wrong with the fuel injectors. With my reader it could only read the TPS (throttle positioning sensor) and the O2S1 (Oxygen sensor 1 which is prior to the catalytic converter). When I let go of the gas, the thought is the fuel injectors will either slow or stop the flow of gas into the cylinder. My test showed that the O2 sensor detected a -10% (whatever that means) in whatever it was measuring. So I went on my run and felt it loose power. Looking down at the reader it was showing a measurement of -8.5 to -9% in the O2 sensor which would indicate from previous test that the fuel injectors were theoretically shutting off. I then proceeded to check out the TPS reading and it fluctuated radically. When I let go of the gas the TPS value never returned to the same value as when left at idle when started. As hesitant I was to take it to the dealer, I decided to anyways. Well 377 dollars later, they told me that the Throttle Body had a lot of carbon build up and they were going to clean out that and the injectors. Afterwards the car ran like new. I have not had enough time to see how long this solution will last but I will keep this up to date on any issues that has come up. Lesson learned is, someone needs to find a new throttle body and injectors immune to gunk build up after such limited mileage for the Aveo.



    2. #2
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      well first your writing skills are impeccable. i dont try that hard on the forum, i spend too much time answering questions to worry about my writing skills.

      second the o2, depending on how it is set up to read. the % is either from stoich, or from the average reading, or a few other possibilities depending on your reading gauge. Having a - number is perfectly normal at times.

      The real problem was the fluctuation in the tps from the throttle body.i am not sure the ready was reading fast enough to show smooth transgression, but the carbon in there is bad and will make it run crappy. It might not translate to the fluctuation in the tps. So keep an eye on it, the tps might still have some issues, or the scanner just wasnt as real time as you thought.




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