My car starts but it bogs down when I give it full gas

  • 2002 DODGE NEON
  • 150,000 MILES
I've replaced all throttle body sensors and air sensors and also have taken catilytic converter off
Do you
have the same problem?
Tuesday, September 13th, 2011 AT 6:36 AM

1 Reply

The first thing to do is put the converter back on. It's efficiency is monitored by the Engine Computer. When no change takes place to the exhaust gas as it goes through the converter, the Check Engine light will turn on and a related diagnostic fault code will be set in memory. That will prevent the computer from performing some other system tests and setting fault codes related to those things. By removing the converter you've added another defect to the system besides the one you're trying to solve.

Once the emissions system is fixed, the fault codes should be erased with a scanner, then drive the car to hopefully make the Check Engine light turn on again. When it does, have the new fault code(s) read. That will get you into the circuit or system that needs to be diagnosed further.

By changing random sensors, that added another group of variables to the problem. Every sensor is different and the computer learns their characteristics by comparing them to other things. As an example, if the engine has been off for at least six hours, the computer knows the intake air temperature sensor and the coolant temperature sensor had better be reading the same temperature when you restart the engine. If you replace one of them and they don't agree on the actual temperature, it will take a while for the computer to sort out the new characteristics. Some of that relearning takes place in a few seconds. Some things take many hours or many drive cycles.

What I would recommend is since you know now the throttle position sensor and whatever else you replaced didn't affect the problem, I'd put the old ones back in. The more variables or changes you can avoid, the better.

You might want to install a fuel pressure gauge and watch what happens to pressure when the problem occurs. Chrysler has very little problems with their pumps' ability to maintain the required pressure, but you don't want to overlook anything. Another common approach is to connect a scanner that can display live sensor data during a test drive. Most scanners have some type of record function that will put about five seconds worth of data in memory beginning about two seconds before you press the record button. Later, you can play the recording back frame-by-frame and watch for clues in the sensor readings and injector pulse width.
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Tuesday, September 13th, 2011 AT 7:37 AM

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