Mechanics

01 POOR ACCELERATION

2001 Plymouth Neon • 4 cylinder 2WD Automatic • 147,000 miles

I have a 2001 plymouth neon, when I stop at stop lights the engine idles really low and car shakes, when I put it in neutral it stops, my acceleration in the car is completely horrible, I can have the pedal to the floor and it takes forever to get to 50mph please help
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Callis44
July 15, 2011.




Has the Check Engine light turned on while you're driving? If so, there are diagnostic fault codes stored in the Engine Computer. Most auto parts stores will read those codes for you for free.

Caradiodoc
Jul 15, 2011.
Never threw any engine codes

Tiny
Callis44
Jul 15, 2011.
"when I put it in neutral it stops"

What stops, the engine or the shaking? You may have a simple misfire but that should be detected by the computer. A worn or broken engine mount can cause a horrendous vibration that will change depending on how much load is on the engine and whether it's in gear or in neutral.

The first thing to do is see if there really is a misfire occurring that isn't being detected. One thing the mechanic can do is connect a scanner that reads live sensor data and view the "AIS Steps". That's the automatic idle speed motor. Out of 256 positions the computer can set it to, step 32 is typical for maintaining a normal idle speed on a good running engine. If one cylinder is misfiring, that will jump up to around step 50 or higher.

Caradiodoc
Jul 15, 2011.
I just changed the spark plugs, wires, and coil. The low idle stops when I put it in neutral, the rmps raise to 1000, when in drive at stop lights it drops below 1000 and almost stalls. This and the poor acceleration, verrrry poor acceleration leads me to think it its the throttle positioning sensors. Idk though

Tiny
Callis44
Jul 15, 2011.
Ahh, more variables. The throttle position sensor just tells the computer what you're doing. It has very little effect on how the engine runs. Did you replace the parts to try to solve the problem or did the problem start after those parts were replaced?

Caradiodoc
Jul 15, 2011.
I replaced them to try and solve the problem, there was a compression test done recently on my engine and it was good, so I know there isn't any misfires or bad cylinders. Possibly dirty fuel injectors?

Tiny
Callis44
Jul 15, 2011.
Wrong conclusion on the misfires. Three things are needed for a cylinder to produce power; fuel, air, and compression. The one that causes the least problems by far is compression. Just because it was good means nothing as far as misfires are concerned.

Chrysler has the least trouble with injectors among all manufacturers so look at them last. Most misfires are caused by ignition problems, (spark plugs and coils). That would be typical of the shaking you mentioned.

Low power can also result from a plugged catalytic converter in the exhaust system, although that will make the engine run uncommonly smoothly at low speeds. You'll also hear more of a hiss from the tail pipe instead of the normal "putt-putt".

Low fuel pressure can cause running problems, but the typical things that happen usually result in stalling while coasting, not while accelerating. I'd suggest borrowing a pressure gauge but the readings don't mean much because they change according to engine load. If there's no fault codes, the best plan of attack is to connect a scanner to see what the sensors are reading. Otherwise you're guessing and that's the least effective and most expensive way to diagnose it.
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Caradiodoc
Jul 15, 2011.
Okay will do

Tiny
Callis44
Jul 15, 2011.
You would need to get the fuel pressure checked on this car. Sounds like a bad fuel pressure regulator to me.

Tiny
Ausername123456
Jul 15, 2011.
Very uncommon on Chryslers.

Caradiodoc
Jul 15, 2011.

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