Q: Replaced crankshaft position sensor, runs worse 2003 Chevrolet Tahoe

asked by on December 18, 2016

My vehicle has been running rough since last night (Saturday December 17). It would start up fine and run smooth, but after a mile or two it would suddenly lose power and rpm's dropped like a lead weight. After allowing it to sit for a minute or two, it'd start back up fine, then a couple miles later it would repeat the process. I tried changing the fuel pump, since it seemed like a fuel issue, with the way the engine acted like it was running out of gas. That didn't help. So I did some asking around and digging online, and found from other people's experience with the same issue, it was the crankshaft position sensor. So I picked up a new one and changed it out, without issue. But now when I turn on my truck it idles very rough and has very little power when pressing the gas pedal. It sounds like it's missing in the engine. And if you take your foot off the gas pedal the engine putters roughly for a second or two and shuts off. All electrical works good as well. So I don't know.

My car has 225000 miles.
My car has an automatic transmission.

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Hello - there are several possibilities for this kind of behavior. While it’s possible the crank position sensor could fail in this fashion, fuel supply (as you first thought) is also a real possibility. A failed fuel pump relay will act in this manner - run for a bit, get hot, stop passing current to the pump, stop pumping fuel - cool, repeat. In your defense, a failing fuel pump will act the same way! I would replace the fuel pump relay and fuel filter, then check fuel pressure while running (and losing power if this continues) to verify correct fuel pressure. Clogged or otherwise malfunctioning injectors can also act this way. I would recommend an engine inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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