I have a 99 Dodge Neon with about 107k miles. When I start the car its running very bogged down and almost stalls. after I hit the gas to rev it, it sounds somewhat normal but still has a very rough idle(also I can hear like a puff, puff,puff noise from the exhaust). When I drive and come to a stop light or stop sign and stop fully it idles rough and when I hit the gas it stubles for a second but goes. At higher speeds(55-65 mph) it runs fine. I have replaced the spark plugs and wires, tested the ignition coil, and tested the fuel injectors. The spark plugs(had replaced about 30k miles ago) were black. Also I have a check engine light that comes and goes for an O2 sensor(not on now). I've been told EGR valve might be bad and also heard that this faulty O2 sensor could cause this. Anybody have any suggestions?

 

Rough idle problems can be endless. Go to an auto store and have them pull the P code for the check engine light. That will narrow down your possibilities.

Possibilities are:
fuel pump
fuel filter
spark plugs and/or wires
coil pack
fuel rail
fuel injectors
O2 sensor/s
disconnected vacuum line
and so on...

 

Thanks for the reply. I replaced the plugs/wires tested the coil pack checked the fuel filter/fuel pump. And still running the same way. My check engine code is p0139. I'm going to replace the 02 sensor to see if that helps

 

Before replacing the O2 sensor, check the wiring at the pcm. Check the resistance of the O2 wires from the sensor to the pcm. Could be faulty or corroded.

 

Today I took my neon to a shop. The o2 sensors seemed fine. They ran my check engine code and I have a p0108 for the map sensor having high voltage. But no code for an 02 sensor that was there a month ago. I'm gonna have the map sensor replaced. Hope that fixes my problem. Again thanks for the reply

 

I wanted to update this to see if anyone can help. I replaced the map like I said and had the code cleared but still not acting right. I was told to check the coil pack and the its reading 12.5 ohms on the steel where the wires plug in but where the electrical connector plugs in the ohms are 1.3-1.5. I have one of those tear and rebuild books and it says in there where the wires go should be 11.5-13.5 which is good but the electrial connector goes it says .45-.65. Could this be my problem?

 

You want low ohm resistance for your wires, but that sounds real low for stock wires. They may be faulty. Granatelli wires have 2 ohms of resistance that go on the neon. Buy a set and replace your wires and see if it helps. Also pull your plugs and have a look at them. If the wires don't fix the problem, you can always take them back.