I have been trying to run down a problem with a 2002 Neon AT. It idles fine, but misses, stumbles and backfires out the intake when put under load. If you ease into the throttle it isn't as evident, but I can still feel it. When pushed hard I get a cyliner 2 misfire. I have replaced the plugs, wires, and airfilter. I have replace injector o rings, and done a seafoam and injector treatment in the tank. So where do I start next? I dont know if it is fuel or spark as these can be tricky. It has only 42k miles. I am leaning toward fuel as backfireing is often time associated with lean mixtures or timing. I will be checking the fuel pressure on the rail and see if that is within specs. I am not sure about where the fuel filter is, but seems like low miles for a change. Let me know your thoughts. Thanks.

 

take a look at all ur parts in the gas tank.

 

Fuel pressure is 58lbs. at idle and 3000 rpms. So fuel pump, reg, filter all should be good. Problem is cold or hot. O2 must be ok. Scan Tools shows it working. Strange I cannot read the rpms on the scanner. I usually can. Probabaly not related. All connections on coil pack good. Think I'll try cleaning the TB, but I dont have confidence this will help. Wonder if the CKP(cranksensor)or CMP(cam sensor)could cause this?

 

I had the same problems with my MSD coil. I put my stock one on and I've had no problems in almost three months. The MSD is now part of a Oregon land fill.

 

In the meantime if you have to drive the car I'd run some high-octane fuel through it until you fix the problem, because it sounds like you're pre-detonating and that's the last thing you want to do, especially at high rpm's (kaboom).

 

I think the coils are OK or at least they check out ohm wise on the primary and secondary side. Could be they are failing on demand, but most likely not. I ohm the injectors and all are 16.5 to 17.2 ohms. Specs say 12, but I suspect heat is the culprit. They are so close, to one another I think they are fine as well.
Still, I guess it could be a bad wire, but it's a long shot. I suspect a sensor or some sort. I wouldn't think the IAC would impact this on high rpms how about you? How would a badTPS act?

 

My coil checked out. The problem was when it would get damp. It would kill it. Mine did it twice the first time I took it off for awhile, I put it back on it ran fine for a month or two. Then last fall when it started raining and foggy mornings it did it again. So I took it off and put the stock one on and no more problems. When it would act up I could not give it power. I had too idle around till I got home.