2000 Plymouth Neon Car hesitates accelerating after coming

Hi bccompsci. Welcome to the forum. First you have to figure out if this is engine or transmission-related. If the transmission is the problem, the engine will speed up normally when you take off from a stop light but if it's slipping, the car will accelerate slowly. That usually is not intermittent; it will happen all the time, and there will typically be delayed shifting problems too. If it's engine-related and you have a tach on the dash, you will see the engine speed does not pick up when you press the gas pedal. I had a similar problem a few years ago with my '88 Grand Caravan when the pickup screen inside the gas tank became plugged. That only acted up for the two hottest days of summer, then was fine for the next six months. The clue there would be the engine likes to stall when letting off the gas, such as when coasting down from highway speed. That doesn't exactly match your symptoms though.

If you determine it's an engine running problem, your mechanic can drive the car with a scanner connected so he can view live sensor data as it occurs. Most scanners have a record / playback function that allows him to take a snapshot of what the Engine Computer sees from the sensors. The "record" button is pressed when the problem happens. Since the data travels through the scanner's memory, the recording actually starts a few seconds before the button is pressed. Later, he can replay that data slowly to watch for signs of incorrect sensor data that will lead to a solution.

Caradiodoc

Chrysler is the only company that lets you check for codes yourself without any special tools or crawling under the dash as in the case of older GM cars. On older cars like the stuff I drive, you count the flashes of the Check Engine light. I think yours is new enough that the codes will display in the odometer readout. Cycle the ignition switch from "off" to "run" to "off" to "run" to "off" to "run" three times within five seconds, then watch the odometer and record the code numbers. If the engine cranks for even a fraction of a second, that will abort the test. You must turn the ignition switch off, wait a few seconds, then start over. On older cars from before '96, I believe, the Check Engine light will flash a number of times with short pauses between flashes for the first digit of the two-digit code, then there will be a longer pause, then the second digit will flash. After that second digit there will be an even longer pause, then the next code will flash the same way. Some cars start with code 12. That one can be disregarded. It just means the ignition switch was turned off recently. The last code will be 55 which just means "end of message". If you think you miscounted, on some models you can just cycle the ignition switch off once and back to "run" to start the sequence over.

Not all codes turn on the Check Engine light. Some are minor such as code 17, "Engine running cold too long". Every Chrysler product will set that code up here in Wisconsin in the winter because it takes longer than six minutes to reach normal operating temperature. The light will not turn on for that code. You can tell the severity of the problem by the way the Check Engine light behaves. When the light turns on, the problem detected could have an adverse effect on tail pipe emissions. The least significant ones will turn the light on while the problem is occurring, and the light will go off if the problem goes away. For more severe problems, the light will turn on and "latch" on or stay on, even if the problem corrects itself while you're driving. The light will turn off when you stop the engine, and it will be off the next time you start the engine until the problem occurs again. For still more severe problems, even if the problem corrects itself, the light will be on anytime the engine is running, even after it is restarted and the problem hasn't occurred again. The most severe problems are when the light is flashing while driving. That means way too much raw fuel is in the exhaust system and the catalytic converter is going to be damaged if you keep driving.

Any codes will erase automatically after around 50 engine starts if the problem was intermittent and hasn't occurred again. That takes about two weeks.

As an alternative to the dealership, many auto parts stores will read the codes for you for free. Obviously they're hoping to sell you some parts, but it's important to understand that the codes are only meant to identify the circuit or system with the problem, not necessarily the defective part. As an example, a code related to the throttle position sensor is almost always resolved by replacing that sensor, but the key word is "almost". There are three wires for that sensor. One could be cut, rubbed through and shorting to the engine, or a connector pin could be corroded. Many people just throw a new sensor on the engine and hope that takes care of it, but professionals will make a few voltage measurements first to verify the sensor really is the problem. The only reason I mentioned that is too many people think you just read the code and change a part and that should take just a few minutes. In reality, the codes are just one piece of the troubleshooting procedure. The codes make it helpful knowing what made the Engine Computer upset, but there are many things that are not monitored by the computer and won't set codes or turn on the Check Engine light.

Caradiodoc

Happy to hear the problem is solved.

P1684, (P for power train) just means the battery was disconnected within the last 50 starts. The significance of that code is if there is an intermittent problem and the battery was NOT disconnected, (or run dead), you could expect to find something causing an intermittent break in a wire or somewhere in the circuit that keeps the memory alive in the computer when the engine is off. Common things would be corroded pins in an electrical connector or loose or dirty battery cables. More likely someone did disconnect the battery while performing other service so you can disregard that code. It will erase by itself soon.

Caradiodoc

I come up with a totally different description for that code. I have a 2000 Cirrus / Stratus service manual, and a 2001 Neon manual. In both, that code is for "Inlet Air Temperature Circuit High". Two-wire temperature sensors, whether for air, coolant, or battery, have an extremely low failure rate on Chrysler products. More likely you will find a sensor was momentarily disconnected while the ignition switch was turned on, (that's when the Engine Computer will notice those things), or there is a problem in the wiring going to that sensor.

"Circuit High" means the voltage on the sensing wire went up to the 5.0 volt supply voltage. That happens when there is a break in a wire, as in disconnected. A different code would be set if the wire insulation was rubbed through and the wire was grounded, (touching the metal body or engine).

Caradiodoc