p0303, Check Engine Light

OK, I'm just here to see if anybody can save me some time and testing as I am fully ASE certified but not at all familar with American cars let alone the Dodge Neon.

I have a friend with a 2003 4 clyinder Dodge Neon.
Continuously throws a p0303 DTC, Cly #3 misfire.

My first step was to replace that plug. I used a replacement NGK spark plug and cleared the code. A few days later the Check Engine Light returned.

I've found that upon disconnecting each clyinder's injector connector that clyinders 1, 2, and 4 stall the car out while number 3 only makes the car run a little more roughly. In seeing this I thought to swap the injector for clyinder number 3 with that of another clyinder to see if the problem would follow the injector, however, disconnecting number three's injector only lead to a rough idle as opposed to a stall condition.

On a hunch I proposed an ignition coil. I installed the ignition coil and the car ran under the same said conditions; cly 3 misfire and only cly 3 injector does not stall engine. After driving the car, the car had a p2102 DTC for a bad coil... so I swapped the old coil back on.

So my question is this... how sensitive are these neon's to aftermarket spark plugs? how commonly do their ignition coils go bad? and, is there anything I should know about a p0303 on this car? ie TSB's, reprograms, similar experience. I have yet to test compression... should I be? Are these engines commonly loosing compression?

Thanks for any help that anyone can provide.
Anymore information that anyone may want can be provided.
I look forward to your responses.

NGK's should be fine as long as they are copper and not platinum or split-fire. Did you check the spark plug wire for any cracks?

spark plug wires appear fine. no arcing, as car regularly misses. tested for any humid arcing with a spray bottle but found nothing...

any other thoughts?

thanks a bunch>>

I would say the injector, but I see you already swapped it out. Did you replace just the 1 plug or all 4?

I would be thinking a burnt valve or cam/lifter problem.

i replaced just the one spark plug as i happen to have one laying around. so it has one nkg plug and thee champions. do you think this could repeatedly through a misfire on the same cly?

yea, i did swap the injectors from one cly to another and it stayed on number three... so injectors themselves seem to be ok but if they have the correct pulse, i don't know.

a burnt valve eh? i have yet to check compression or leakdown. anyone know what is considered good compression in this thing?

thanks again for your input everyone>>

I'd replace all four plugs just for kicks, you never know!They are cheap enough. Compression should be around 170-190.

Ok- as soon as I can get the car back I'll be doing a compression test and replacing all plugs with factory to see where I'm at. I'll post results for anyone interested.

Does anyone know off the top of their head what the factory warranty is on this thing? 2003 Neon-

NGK's should be fine as long as they are copper and not platinum or split-fire. Did you check the spark plug wire for any cracks?

Why not planinum? I was always told that platinum was better than copper.

Why not planinum? I was always told that platinum was better than copper.They work well on some cars, but not the neon. The neon has a waste-spark ignition, so we see no benefit from platinum or split-fire plugs. My wifes sebring however, requires platinums only because they are a PITA to change.

They work well on some cars, but not the neon. The neon has a waste-spark ignition, so we see no benefit from platinum or split-fire plugs. My wifes sebring however, requires platinums only because they are a PITA to change.


Ahhhh...I see. Does that mean that platinums are bad for a Neon if they're already in there?

Ahhhh...I see. Does that mean that platinums are bad for a Neon if they're already in there?YEP!!! No neon comes stock with platinum plugs, not even the SRT-4.

only 75ish psi on cyl number three.
all of the others were close to 200.
thanks guys>>