So we bought an '02 Dodge Neon (base) (auto, SOHC), with 142,000 miles on it, great body solid car, but we are having a problem with a rough idle, poor mpg, and it's throwing a code.

When we went to pick up the car the guy was finishing installing new wires, and a coil pack, not sure if he did plugs or not. The air filter looks pretty dingy so that will have to be changed also.

I ran sea-foam through the intake, and than latter that day it gave me a P0420 code, catalytic converter running below threshold.

I put a new upper motor mount in it Saturday, and that seems to have smoothed things out, but still shakes at idle.

As for MPG she is getting about 180-200 miles per tank

 

I would check the car for exhaust leaks, and check the cat to make sure its not plugged. I would make sure he did plugs and gaped them correctly. Have you checked the compression to make sure the motor is up to standards.

 

we have had this car for a few months cant figure it out. we have replaced...pcm, battery, battery cables, spark plugs and wires, alternator, fuel pump, oxygen sensor. we took it to a dodge dealer paid to find out what is going on said it was the pcm we have replaced it and reprogramed it and it is still doing it. some days it runs fine others it acting like it wants to die and has died on me a couple times....the car starts to shake and idle rough.... i can come to a stop light and i know when it is going to do it. i can try to give it gas and it does nothing it revs up on its own and smooths out.check engine light comes on and goes off reading oxygen sensor that we have replaced more than once..but tht is the only code...any ideas?????

 

What o2 sensor code is it throwing? Having a check engine light for the o2 can mean more things then a bad sensor. Could be a plugged car or a fuel issue. I would check exhaust restriction, and fuel pressure. On an issue like that it would help to use a good scanner and watch the sensors to see whats going on. Things like map sensors, TPS, coolant temp, and so on can cause similar issues. I would ask the dealership for a refund on the misdiagnosis, or tell them to fix what you paid them to fix.

 

we have checked the fuel pressure it is ok...the sensor is p0132...and i called the dealership back and they said tht that was the first step that i would have to bring it back in and see what its reading now and i had to pay again...lets just say i was not happy....we had never heard of the first step crap ...we want to figure out what its doing...

 

Check/replace the O2 sensor and wires.
Cat may be clogged or parts may have broken off and lodged in the exhaust. Doubt it but it happens.

Pull the spark plugs and check for oil in the tubes. Spark plug gap and condition. Correct type of spark plugs.
Shaking is either uneven compression or misfire.
If you feel like playing do a compression test while the spark plugs are out.

 

I had it checked out, and had the cat replaced, and the upstream O2 sensor replaced. It still shakes a little. The spark plugs look good, a little gray on the electrodes, no oil on the boots. I replaced the upper motor mount.

 

I can't win with this car, so far I've replaced both O2 sensors, the cat, IAC, TPS, did an oil change. After I changed the TPS, IAC it runs better and stalls less but it still drops the idle and idels rough when I come to a stop.

 

Is there any oil in spark plug tubes? What kind of spark plugs did you use and did you gap them? Other silly questions like the last time you changed fuel filter.
No codes other then O2? You are still getting O2 sensor code? Wire harness can be a problem. CPS, O2 sensor and a couple of other circuits share wires.

Camshaft and crankshaft sensor... Had it run and stall sometimes with a failing crankshaft position sensor. Ran for months before it finally died on me. Had oil in spark plug tubes too so I thought that was causing the problems.

Was the coil pack he put in new or used? Start the car up and spray with water. Do so on any vacuum lines, coil pack, spark plug wires, intake manifold, and see if there is any change in idle. Don't mean hose engine down... just a spray bottle.

Check the fuel injectors. with car running you can pull the wires off the fuel injectors and again, see if idle changes. Try the same thing with the spark plug wires.
You can also do a compression test.

Don't want to tell you to replace the fuel pump. That can also cause issues like poor performance. They die in different ways too. If you can get one cheap at a salvage yard... it takes like 20 minutes. Test before you replace.

Can you post a video on youtube of the car in action? Really helps to hear it running. Spit balling ideas but with problems like that and nothing but an O2 code or no codes it's really a process of ellimination and checking darn near everything. Are you in New York state? If so bring it by next weekend and and we can play

 

No oil in the spark plug tubes
not sure what kind of plugs he put in but they are gapped correctly
I haven't done anything with the fuel filter, but I was under the impression that it was non serviceable.
No more O2 sensor code, but it is getting a gas cap code, and a hole in the EVAP code
The coil pack and spark plug wires he put on was new