Car surges while driving

2000 PONTIAC GRAND AM
231,646 MILES • 3.4L • V6 • 2WD • AUTOMATIC
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CHERYL NICOLS
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So this problem just started after we basically combined two of the same cars into one, lol. No problems upon starting and runs fine right off the get go but after it is nice and warmed up and cruising along, it will randomly start surging and decelerating slowly to the point of only allowing you to drive around thirty to forty mph's and still with the occasional surge. we discovered that while It is doing this if we shift it into neutral and shut off the engine (while still driving) and then start it again quickly, the problem stops and u are able to accelerate to normal speed with no problem. It sometimes does it repeatedly and sometimes can run for hours without doing It all. We checked all the normal things that would cause this, fuel system is fine, catalytic converter is okay, vacuum lines are fine etc., all we can think is maybe it is the ECM causing it. Any help?
Apr 27, 2018 at 9:00 AM
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STEVE W.
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Explain what you combined? Same exact year make model engine transmission? Why did you combine them - one bad engine or? Just trying to determine if something might not match up, like a sensor may look the same but not actually be the same, or perhaps one had an issue that is now showing up.
It sort of sounds like a fuel pump issue. Once you do the shutoff/restart does it run fine the rest of the day or does it go ten miles and need the "reset" again?
Apr 27, 2018 at 12:27 PM
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CHERYL NICOLS
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All we switched was the engine from one into the body of another, did not change anything and sometimes it will fix it if and sometimes it will make you do it again and again all day.
Apr 27, 2018 at 3:32 PM
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STEVE W.
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From that I would look at every wire connection. It sounds like it goes into closed loop and then starts acting up. They were both 2000 vehicles correct?
Apr 28, 2018 at 8:47 AM
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CHERYL NICOLS
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Yes exactly identical. And what does closed loop mean? The check engine light is on and we put it on the code reader and it is throwing these three codes n/a p0341. P0135p
Apr 28, 2018 at 1:26 PM
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STEVE W.
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When the car is first started the computer only uses a couple of the sensors to actually run the engine (open loop). Once it has run long enough that the oxygen sensors and converter are active the computer switches to using feedback from all of the various sensors to operate the engine (closed loop).

P0341 - Camshaft Position Sensor Circuit Range/Performance.
P0135 - Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1).

Both are circuit codes, which could mean a failed part but most of the time it turns out to actually be a bad wire or connection causing the problem. In your case the cam sensor code would be the one causing the surge. The fact that you can shut it off and on restart says the sensor works but it's having a problem.
I would start at the sensor connector and follow the harness, look for pinched or damaged wires.
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Apr 29, 2018 at 6:28 AM