sporadic misfires - 97 neon

[neoncrazed]

I have a 97 neon highline 2.0 SOHC. It has had sporadic misfires.

A month ago, it had a brief episode (few seconds) of very rough running, and the SES light came on. My OBDII scanner showed P0304, misfire on cylinder 4. I cleared the code and turned off the SES light. After that, it ran perfectly fine for a month.

Yesterday, I started it up cold in the morning and it idled very rough, as if on 3 cylinders. The SES light was flashing at first, then steady. After a few seconds, it ran fine and has been since. The OBDII revealed P0303, so this time cylinder 3 misfired. I cleared the code and turned off the SES light. Two more cold starts, one last night and one this morning, were problem free.

I have read about the most common causes of misfires: plugs, wires, coils, cam sensor... But instead of replacing parts "blindly", I was hoping that the pattern of symptoms could help pinpoint the problem, or at least exclude some possibilities?
What is the most likely cause, being the misfires happened in two different cylinders, but most of the time the engine runs perfectly?

Any input would be appreciated - Thanks

[NeonStyl]

If you have a multimeter, you can test almost all the "suspect" parts without having to blindly replace them. Test the plug wires, coilpack & sensors... the procedures to do this are listed in a Haynes manual.

Also, since you would have to remove the plugs anyways to check them and they are typically only $5 bucks or so, I would simply just replace the plugs with a new set.

Champion RC9YC or NGK V-Power #7373 are the recommended plugs for your vehicle.

L8R,

[neoncrazed]

Originally Posted by NeonStyl

If you have a multimeter, you can test almost all the "suspect" parts without having to blindly replace them. Test the plug wires, coilpack & sensors... the procedures to do this are listed in a Haynes manual.
Also, since you would have to remove the plugs anyways to check them and they are typically only $5 bucks or so, I would simply just replace the plugs with a new set.
Champion RC9YC or NGK V-Power #7373 are the recommended plugs for your vehicle.
L8R,

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Thanks, NeonStyl, I'll follow your advice. - neoncrazed.
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'97 Neon Highline SOHC, off-the-rack, 60 K miles

[clariveros]

Hello, i am havign a simiar problem but it is i have only gotten the p0304 code and the weird thing is that the first time it did this was like a year ago and now it did it again last week. so i am wondering what it could be also do the 99 neons come with platinum spark plugs or just hte regular kind because if it is the regular kind i think it is time for a tune up?

[clariveros]

Originally Posted by clariveros

Hello, i am havign a simiar problem but it is i have only gotten the p0304 code and the weird thing is that the first time it did this was like a year ago and now it did it again last week. so i am wondering what it could be also do the 99 neons come with platinum spark plugs or just hte regular kind because if it is the regular kind i think it is time for a tune up?

oh yeah the car only has 40,000 miles on it

[palindromelol]

I had an identical issue. The plug from the harness jiggled loose where it terminates in the coil pack on top of the engine. I siliconed it in place. Intermittant issue it was. had misfire codes until I eventually got coil codes.

I also had a cracked plastic retainer which holds the injector wires in place. I wrapped a pull-tie around it.

[das2123]

Originally Posted by clariveros

so i am wondering what it could be

Cylinder misfires are generally faulty spark plugs.

Originally Posted by clariveros

also do the 99 neons come with platinum spark plugs or just the regular kind because if it is the regular kind i think it is time for a tune up?

Do not put in platinum spark plugs, they are no added benefit to the neon. Buy some of the stock champions, reset your PCM and you should be good to go.

[clariveros]

thanks man i will do those things

[Hollowcreek]

Was getting the same codes on a 97 and found that the valve cover gasket around #4 was leaking and when enough oil accumulated in the hole, it would get under the plug boot and onto the plug and wire and cause a voltage drop triggering the misfire code. A new gasket did the trick, that and being careful not to overfill when the oil was changed.
If you are finding oil in there when you check the plugs, thats probably all it is.

[clariveros]

well, just an update, this is my GF's car so mind you that i am just getting around to make sure all the proper maintanence has been done, and let me just say that, the spark plug were never changed so they were almost gone , I replaced the plugs and this seemed to do the trick, the car is running fine so i am making sure that all the maintenance is up to date on it, thanks all

[das2123]

Originally Posted by clariveros

well, just an update, this is my GF's car so mind you that i am just getting around to make sure all the proper maintanence has been done, and let me just say that, the spark plug were never changed so they were almost gone , I replaced the plugs and this seemed to do the trick, the car is running fine so i am making sure that all the maintenance is up to date on it, thanks all

Good to hear it. Alot of people fail to change their plugs and do simple routine maintenance and then freak out when all hell breaks loose. As a matter of fact, I need to change my plugs, LOL...Anyway glad you got it fixed!