98 Plymouth Neon

It seems I have a problem with my DOHC Neon. I have a code 12 and 43.

Originally I had only a code 37 (I believe it was), which was for the radiator fan relay, which I replaced.

After that, I cleared the codes, then got the codes 12 and 43. I replaced the coolant temp sensor, and the code cleared, but it is now back.

I have what feels like a misfire in acceleration. I have also replaced my spark plugs, and the old plugs looked fine, maybe a little lean, but otherwise ok. The wires are fine.

The car starts fine in the morning, and doesn't feel like it is going to die, it just has a shuddering at certain speeds or under load. The CEL flashes when this occurs as well.

Code 12 is common, battery disconnected during last 50 key starts. Code 43 is a misfire, so check all of your plug wires to ensure nothing is stuck up in the wire where it goes onto the plug and check the plugs, (especially if you have the type that the top can unscrew like Champion) to ensure the caps are on tight and not stuck up in the plug wire.

Try to get the "P" code for the misfire. It will give you a little better indication of what the problem is. Code 43 can be alot of things.

Well, I got the P codes:

P0300b multiple cylinder misfire
P0301b cylinder#1 misfire
P0304b cylinder#4 misfire

Wires seem fine (MSD wires/coil), haven't tested the coil (don't know how - about 6-7 years on the coil - not many miles)

Try swapping the wires around and see if the cylinder misfire changes with the wire. Inspect the coil pack for any cracks. Try cleaning up the leads on the coil pack.

Swapped all the wires around, and the codes disappeared.... for now. I will do some more testing, but should I get a new set of wires anyways?

Wait to see if the cylinder misfires change. If so, then you know you have a wire problem.

Well, the misfire came back.

I changed all the wires, and it is still there.

The coil looks fine, no cracks or corrosion.

I didn't mention, this misfire is intermittent as well. I would be going fine along the highway, when the car starts to shudder and hesitate, but then it resumes normally for quite awhile. Then it may do it again.....

Did the cylinder misfire change or is it still the same cylinder?

It is on cylinder #1 only now.

Might try swapping injectors with a cylinder that hasnt reported a misfire, say #2cyl. - Dirty /restricted injector.
Also Ohm test all four and compare resistances - Might be a shorting injector. Good Luck!

Now it doesn't start at all! It cranks fine, but nothing. Still the same code as well.

EDIT: Code 43 is gone. Now I have code 42, twice. Still doesn't start. Cranks, but nothing else.

Fuel pump is working, I can hear it start up. The relays seems to have power to them. The relays also seem to work. Coil tests fine.

At a loss here now....

This sounds like the hiccuping we had & still have with my daughter's 97 Neon, SOHC. It will run well for 5 to 10 mninutes, then the faster you want to go, the more hiccups it does. It doesnt feel like one cylinder misfiring, it feels like all 4 of them shut down -very briefly-. It causes a very noticeable shudder! Then again it may run fine for 10 or 20 minutes.
I changed the cam position sensor, which didnt eliminate it. I removed the Crankshaft Position Sensor (CPS) to have a look, and the car would not start at all afterward. A new CPS fixed the non-starting, but the misfiring continued. I know my engine wiring harness is in feeble shape from overheating and age - but I dont want to buy a new one from Dodge for over $700.
So this coming spring when I get back to where the car is, I will likely remove that engine harness, and re-create it with new wires and splices,....exactly like the original one was made.
Also I have a neighbor who is a mechanic, tell me that the Neons had a problem on high mileage engines, with the camshaft moving left-right-left, as there is no bearing to hold them, such as many cars do have. With enough wear (our car has passed 160,000 miles) the cam will move away from the Cam Position Sensor - and the signal the PCM expects fades out - and either the injectors or the spark plugs dont get 'fired'.
So if I could really solve the problem, I could get a lifetime supply of Neons to fix up - for very little $$.