My friend needs help with his Neon
 

My college roomate is not so knowledgeable about cars, so when he got desparate to get one he sort of bought what he saw first. He needs a car to go from NORTH DAKOTA to IOWA every other week:yikes:. Despite my advice he bought a 2003 Dodge Neon from a dealer with 140,000 miles and I won't go into what he bought it for.

On the way back from his trip the engine light came on and when you let off the pedal, there is a knocking sound when deccelerating, sounds relivant to RPM of the engine. Sort of sounds like the bad road noise you get on a poor concrete road. Can only replicate when coasting or braking. Any idea what can be the cause? Definatley taking it to the mechanic but would like some other opinions. Thanks.

I saw this happen to one Neon twice and the car went through 2 motors before they got one that didn't make any sounds. The bearings for the connecting rods ended up wearing out due to poor maintance and would knock like crazy.

So what would be your advice? Try and sell it and take a loss? Sounds better than having to replace the engine.

Does it knock while sitting still, reving the motor ? Could be a drive shaft problem if it only does it going down the road.. I would have it checked and then make a decision about the repair

Only in driving. Reving the motor doesn't do anything.

Are you sure its an engine noise? Check the CV joints and the rest of the drivetrain. How does it sound when it makes a sharp turn? The check engine light may not be connected to the noise problem at all.

If it is only while driving then most likely it's not going to be the motor. It'll be something that is rotating while driving like the axle shafts, hubs, rotors, etc..