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Symptom:

When I try to accelerate, probably 7/10 times, it will "choke" or "buck" for a split second, drop RPMS, then pick up and continue without issue after this. It seems like it only happens when i accelerate fairly quickly, but that could just be because the RPM drop gives a more noticeable jerky feeling.

The car is running fine other than this. There's a small exhaust leak I can hear/smell but nothing too bad, and there are NO DIAGNOSTIC LIGHTS. The only time I've seen a light is when I was trying to recreate the issue, a few times I got the "Electronic Throttle Control" light (red lightning bolt) indicator to come on. I did this by slamming my foot to the floor fairly quickly to test the acceleration, and when it happened the car simply wouldn't accelerate until I released the pedal and pressed it again. Then the light went out. I got this to happen a few times.

Have recently done minor maintenance: oil, plugs, filters. Nothing major.

So many proposed theories from friends/relatives that are more mechanically inclined:

  • Fuel System (injectors,filter,pump): I have a hard time believing this, because I would think this would be more consistent than it is? However this is a lingering thought
  • Transmission: This seems like an odd fit because it's not during shifting, it's during a period when the car isn't trying to shift and won't be for quite a while.
  • Sensors: O2, Mass Airflow, etc... but I would expect a code from these?

My working theory is that the pedal position sensor is flaky in some way, maybe a small dead-zone, which when hit is telling the throttle body to restrict intake momentarily. This would align with the indicator I got to come on at one point. I'm going to try to get the pedal hooked up to an analyzer this weekend and see if I can see anything funky, should be simple enough. The only thing that doesn't add up with this, is again why there's no code? Does it only throw a code if multiple sensors don't agree, or would it throw a code if it sees something like an anomalous dead-zone? I'm an engineer so I understand a good portion of the electrical system, but little out of my depth when it comes to check engine light codes and what actually causes them to pop.

Any input is greatly appreciated!

  • Welcome to Motor Vehicle Maintenance & Repair! – Cullub Aug 24 '18 at 16:32
  • How do you know there’s no code? Because the light isn’t on? Not all codes will set the MIL. Set criteria for sensors are circuit codes high/low/no response or performance codes. Throttle or APP sensor codes will set for those above or if the app or tps sensors don’t agree. The red triangle light indicates a etc system error. Try cleaning the throttle plate and resetting the adaptive memory with a scantool first. When accelerating is it misfiring or only hesitating? – Ben Aug 24 '18 at 16:52
  • "Not all codes will set the MIL", this was something I was afraid of, will get it connected to scanner soon. Not sure I have enough experience to identify the difference between a misfire vs hesitation. The feeling is basically like pulling your foot off the pedal, or even hitting the break momentarily. If you're accelerating pretty hard, it's a pretty powerful momentary jerk/hesitation. – While-E Aug 24 '18 at 17:05
  • Was throttle body, swapped out and car is snappy, responsive, and no bucking – While-E Sep 12 '18 at 21:28
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Sounds like throttle position sensor Little bit of deleay between it and computer.try reset and a good cleaning might straight it out . Have one timeing advance sensor got s little slow on mine through trotle off.now that was a bad week hunting it up just thought. If gas firing and timeing not on money you can get hesitation if either of a blink either way good luck hope it works out for you.one last thing you might check air filter and sensor at breather box may be smothering a for air could cause her to bog while getting Right air mix.Just a thought

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