I recently purchased my car (2003 Dodge Neon), I have had a lot of problems, but the most recent ones has been with shaking, I have had my engine mounts replaced twice they thought that was the problem, I noticed that when I accelerate the car doesn't shake, but as soon as the car is idling that the shaking starts again, if I turn my rear de frost on or anything with air or heat that the shaking is worse, I have also noticed that the car idling lower (usually at the 500) mark, seems quite low, I'm new to this, someone help, is it an electrical issue, engine mounts, or something else? Help!

 

I had this issue as well last year. It drove me nuts. I had already done the motor mounts, shot anyways. it helped but it was still very bad when at stop lights, especially during the cold and when i had the AC or Heat on (added load to engine). If you just tap the accelerator, just enough to engage the throttle cable it will go away. that's a good sign of a dirty intake. I eventually just took out the air box and filter, unbolted the throttle body.

Cleaned the throttle body with TB cleaner (make sure its safe for sensors), don't forget to open and close the throttle plate via the lever. Don't worry, there is a lot of crap in there. Pool of black sludge came out of mine (had 180k). I also sprayed in some TB cleaner into the neck of the intake manifold (really didn't feel like removing it) and whipped with a shop rag a few times. A lot of sludge came out of there as well.

I replaced the air filter (about $15) and I also added Fuel injector cleaner to the tank, it was $7 so what the hey. Put it all together, let the car air dry for an hour and started it up. Purred like a kitten. The rough idle was 97% better. All in all i spent maybe an hour pulling it apart, cleaning and put back together and waited an hour and spent under $20. always start with easy cheap solutions. You'll learn your way around the compartment that way as well.

I read about the Neons having idle issues with the TB. Partially a computer programming error that doesn't allow the TB idle position to open wide enough. It's nothing that would throw a code, its all in the programming. Some people drilled a mini hole in the TB plate to allow more air in during idle, i didn't want to do that. The car is 97% better, only small shake at idle. It's hardly noticeable.

Since you just bought it I assume you haven't had the spark plugs or wires replaced. That's less than $50 and I'd recommend doing it especially if the car is over 100k miles. Unless the previous owner has a receipt that has plugs and wires on it for that model or shop receipt always assume it hasn't been done. It can also contribute to the rough idle, if its not firing correctly. Doesn't mean it will throw codes or anything, that's also what the fuel injector cleaner is for. The nozzles tend to clog up.

My Neon is a 2000 with 191k and I did this procedure 20k ago, still running great. My brothers 01 I did this too with 125k and it solved his rough idle as well. It's a cheap and easy thing to do, good preventive maintenance. Worst case scenerio is you did the maintenance ahead of schedule but won't have to worry for another 100k miles. Always start with cheap and easy. Check that stuff first and if you still have an issue there are other things to consider; more on that ball game later.

 

Thanks for the help! Definitely going to have to try this, and will let you know if it works, fingers crossed!

 

Your welcome, good luck! Hopefully that's the issue, i love it when its an easy cheap solution.