97 lumina 3.1 #3 missfire bad plz help

my 97 lumina has a bad missfire, cyl 3. code was p0303, so i changed all the spark plugs they were all white except #3 was black and oily. i also change the coil pack and the spark plug wire to #3. still no luck. some suggestions i stumbled across were the egr valve, oxy sens, low fuel pressure, bad injectoror valve or compression problems. i was wondering if anybody knew which of those would be more likely the cause or if some one else has had this problem had a suggestion. any help would be great, and by the way this happened once last year but quit and it restarted about 4 days ago.

If it's oil, it shouldn't come and go. Did you smell it, and make sure it wasn't wet with fuel over a sooty plug?

Does it blow a blast of smoke when you start it in the morning?

Put a good plug in the #3 wire, ground it on the motor and start it for a second to verify that it is actually firing.

no smells of burning oil no smoke either, but i never thought about seeing if it had the spark ill try that out. also the plug wasnt smelling like fuel or oil really it was just black, not charred but not real fresh or wet looking either

and also i have replaced all the plugs and threw the old ones away so i cant go back and look at it.

any other suggestions

Get a stethoscope on the injector body #3 see if it is clicking, if not it is bad, but it still could be the problem if if there is a clicking, a good scanner can do an injector balance test also.

Since it's just one cylinder, you can rule out all but things specific to that cylinder. All the other things you mentioned would cause problems across all cylinders, not just one. I would do a compression test to see if #3 is lower that the rest. If compression is good, I would lean toward a bad injector, as you said you replaced the plugs and wires. The #3 and #5 wires are close to the same length, so you could swap the two around (on both the coil and the plugs) to see if the problem moves. If it doesn't, and compression is ok, then you need an injector on #3.

thanx ill try swapping them

Replace the #3 fuel injector.The 3.1 has fuel injector problems once in a while.

I have a similar problem with misfire but is on cylinder 2. It only seems too occur when we go from summer to winter fuel mixture. I did change all wires and plugs. can anyone help would the coil pack or fuel injector be the problem. And is it easy to change fuel injector. Email me at snovak0904@sbcglobal.net

Trying to button up some old posts. Turns out after i changed the injector, the fuel line o ring was bad, stores had the wrong one in stock ( all stores, didnt fit the line into the injector body. Car ran ok but not right still. went back and turns out one or 2 of those spark plugs, the brand new ones, were defective. /sigh changed those and it ran till may of this year and the head cracked, (was my sisters car.)

bad injector if its a dead miss

common issue

also on the 3800 engines

just had ot replace injectors 5 and 6 on a 99 lumina 9c6 car about 15 minutes ago due to failure of them,

[now it runs super strong smooth lots of power perfect

driving it right now

try unplugging injector while running

if no change then thats the problem

easy check

swap an injector from another engine etc

dont use a #6 or #5 injector though
because those are the ones that plug up the most common

and are the oens we have ot change always

all the others never have issues