occassional missfire on #3

2003 3400 GA with 90 K on the clock. It occassionally (like once every couple of weeks) throws a random miss fire on cyl #3 code. Originally was told that it was the injector. Replace the injector. Couple of weeks latter, it threw it again. Have been swapping stuff, Swapped #2 and #3 plugs, then the coil packs now Just swapped #3 and #5 plug wires. Have cleared the codes when each change has been done. The plug wires check fine wing a ohm meter.

Also, when in park reving the engine up it will hit about 3800 rpm and then start to surge between 4000 and 3200 rpm.

Need some thoughts.

[lone_wolf025]

Ok random misfire on just one cylinder. You've replaced the injector, swapped plugs, wires, and coil packs. I'd say you got two options left. Check the mechanical condition of the cylinder (compression and leak down test) also make sure that the injector is getting a proper signal from the pcm. Beyond that its gonna be a royal pain to hunt down the cause of one random misfire.

As for the revving in park thats normal. Its to keep you from damaging the engine by over revving it under no load. Basically No Load (neutral or park standstill) + High revs = BAD

[drumking1721]

ummm i hate to like "steal" this thread...ive kinda been havin the same problem on cylinder 2. Only when its wet out,or when my tires spin from it being wet out.My car misfires. My buddy and i were driving around last night and it was snowing pretty good and my car started misfiring,pulled over opened the hood,and the spark was going tot he heat sheild on my header rather than to the spark plug,we fixed that and was running good,just got home and its wet out and my car lost traction and spun the tires and misfired a little,does anyone know what that is from?

[intence]

What did the plug look like when you took it out, it's possible that you put another bad plug in there.

Originally Posted by drumking1721

ummm i hate to like "steal" this thread...ive kinda been havin the same problem on cylinder 2. Only when its wet out,or when my tires spin from it being wet out.My car misfires. My buddy and i were driving around last night and it was snowing pretty good and my car started misfiring,pulled over opened the hood,and the spark was going tot he heat sheild on my header rather than to the spark plug,we fixed that and was running good,just got home and its wet out and my car lost traction and spun the tires and misfired a little,does anyone know what that is from?

thats a bad plug wire and or plug...do some plugs and wires...soon if that keeps grounding all the time, you can hurt your coil packs...

[drumking1721]

thing is it was all new in september,i have the MSDs....i dont wanna have to get a new set.and last time i checked the plug it was good

it prolly melted through on your header....trust me...if you saw spark comming out of your wire...its bad..

[drumking1721]

well yea i know that....the wire didnt melt. I had put electrical tape on it b4 and it had come un down and the spark was coming off that to the heat sheild. No burn marks or anything on the boot. Idk the plug may be bad now.I couldnt tell ya bc we have like a foot of snow out rightnow. I mean it ran smooth this morning,just when i spun the tires is started misfiring a little...

electrical tape won't fix a plug wire....

[drumking1721]

that i know,but i cant do anything about it until the snow is gone

[drumking1721]

im just gonna get a new set of wires...i just took out the 2,4,6 plus and 2 and 4 had gas on them,so my wires on 2 and 4 keep grounding out,does anyone know where i can just get two wires instead of a whole new set?

[gectek]

take the wires to ur nearest auto parts store, they have just individual wires, and also about the other cyl 3 misfire, how did you swap the coils...swap places like the 6/3 w/ 2/5 and also it can be the ICM thatll do that, it uses diff drivers for each signal, and can just go bad on 1 cyl, i know cuz it happened to me. make sure u use the dielectric grease on all the elec connections, including the primary posts on the bottom of the coils. and if they are MSD coils, they have a 1 yr warranty, just take em back and get 3 new ones, thats what i did.

Yes, swapped the 2/6 with the 3/5 packs. these are the original packs.
Hard driving does not cause the code. It is being thrown by just normal driving. Also, being in central texas moisture is NOT an issue. We have very little and none when the code gets thrown.

[gectek]

how far are you away from lubbock? maybe i could take a look

round Rock. Very seldom get up in that area. But thanks.

[gectek]

i think i know someone from round rock, u know a guy named tristan? he goes to tech now, and as for the coil packs you mean you switched the 2/5 pack with the 3/6 pack correct, because u put the numbers kinda funny on there, and if that dont work, and the plug wires didnt work, and changing out the plug didnt work, then i would clean the MAF also, i had a bad maf and bad 3/6 coil that both led to my mifiring on cyl 3.

[drumking1721]

k so yea went for another drive...it misfires in the lower gears...like when im just getting to go and the tire slips a little....it misfires in low RPM

[gectek]

idk, sounds like a little more than just a bad injector or anything like that, may be a bad camshaft or crank pos sensor, but does it do it all the time now, cuz you said 2 diff things, or only when the tires slip. or maybe a bad IC module.

Originally Posted by drumking1721

My buddy and i were driving around last night and it was snowing pretty good and my car started misfiring,pulled over opened the hood,and the spark was going tot he heat sheild on my header rather than to the spark plug,we fixed that and was running good

....

[drumking1721]

it started when i put the new wires on back in sept. Only when it was wet out and the water came in under the hood and hit the boot. So the spark never was getting the real spark amount. I mean when my car runs normal i notice no loss of power and my A/f ratio is great. Its just when its nasty out,ie the last couple days it runs bad. LIke last night with it messing up it misfires when its wet out AND when i loose traction hit ice or snow in low RPM