99 Dodge Neon Missing After Multiple Repairs

[shell.lynn]

Just bought a Dodge Neon from my brother-for the past year it's had the 'Service Engine Soon' light on and has been missing almost always. On the days the light was off, it would not miss. He had it in to our mechanic 2 times this past year, and 2 different sensors were changed, but neither corrected the problem. So now I bought it and our mechanic hooked the car to his computer and said it was the egr or erg or something like that. So $200 later the 'Service Engine Soon' light is now off, but it is constantly missing when stopped or idling or whatever. When I first start the car, I can drive for a good 3-4 minutes without feeling any missing. But after the car warms up, as soon as I stop-It starts missing bad like it's going to shut off on me. Even when it's just idling in 'park' it does this. At least we got the 'Service Engine Soon' light off, right? Also..I don't know if this is normal or not, but the RPM when I'm stopped or parked are above 1 and the needle keeps jumping to like 1 1/2 and back down...don't know if thats something it should do or not. So our mechanic said bring it back in on Monday and he'll hook it to his computer again-but I'm thinking he's had 3 chances this past and obviously is not able to make a diagnoses or fix the problem so hopefully someone here can direct me in where the problem might lie so that I may take it elsewhere this time.

[Godofwarmike]

there might be a vaccum line not connected or cracked. do you hear a sucking hissing sound when its running?

[denisond3]

My daughters 1997 Neon has been doing a similar thing - for the last year. It will run okay for the first few minutes in the morning, then begin intermittent misfiring. It seems worse when she tries to go faster than 50 or 60 mph. Once or twice it has stopped on her when sitting at a traffic light - but always starts up right away. The car is basically in daily use, because the alternative is to walk.
I have read the codes that are set in her car's computer. Some codes will not cause the SES light to come on, or not cause it to stay on; so you cant go by whether the light is actually lit. It depends on the code & how often it happens. Not owning (yet) a scantool, I get the codes read by going to the local autoparts places that will come out to the car and read the codes using their 'scantool'. (Autozone and Advance Auto do this, & probably other places). The codes would say "misfiring detected" - though I didnt need it to tell me that; and would say "no camshaft position or crankshaft position sensor signal detected during cranking".
I have replaced the camshaft position sensor, and the crankshaft position sensor. (Among others over the years)
From reading a LOT of postings to this and other Neon forums, I -think- my problem is one or a combination of the following two: 1. The "engine wiring harness" where it runs behind the motor looks semi-melted and has some corroded wires inside it. This can mess up the signals needed for the Powertrain Control Module (PCM, aka the 'computer') to run the engine. 2. The camshaft may be moving back and forth in its bearings (called endplay), and when it moves away from the camshaft position sensor, the signal may be weak and the PCM doesnt see it. On this engine I dont think there is any 'thrust' bearing to keep the cam from moving left-right a few thousandths. I know there were signs of abrasion on the inside surface of the cam position sensor when I changed it, from being rubbed by the end of the camshaft.
I have -promised- my daughter I would fix it this coming summer; (we live in TX in the winter, and in N. VA. with them in the summers. -- but I still dont know exactly what to fix). !!! I can buy a new wiring harness from the Dodge dealer, but it costs about $700 or more, and its a big job to replace it. There is a 'target magnet' that fits into the end of the camshaft. The original one may have weakened, as magnets eventually do; so I will replace that - and will hope the problem will go away.
If I could come up with a definitive repair for this problem in Dodge/Plymouth Neons, I could own a dozen Neons for pocket change, or could help out lots of folks driving sputtering neons.

I am not at all surprised your mechanic isnt able to isolate the problem and fix it. I dont think Dodge Motors was able to either.
If/when you get the codes read out, you could do a search on this forum for whatever it is, such as a "P0340". You could also get a lot of info by doing a search on the forum for the word "misfiring".
Good Luck.

P.S. Unless your Neon had very low mileage, it probably needed the EGR valve replaced anyway. With age and miles they tend to clog up or stick - due to the hot corrosive gases going through them.