3800 Random misfire.. HELP PLEASE!!

[GTP4ME]

I had a rough idle and then scanned my car and it was showing misfires on the 3 & 4 cylinders. I found that the #3 plug was smashed and closed the gap so I replaced the plug and it helped the rough idle but when I scanned the car it still showed some random misfires in the #3 & #4 cylinders.

What I would like to know is if I am correct to assume that the cause is the coil pack since it shares the cylinders that are coming up as misfires.

Why would the plug get smashed? Could that be caused by the plug itself not firing properly?

Thanks Ahead for any responses,

Jamie

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[syP]

do you have a scanner?? if so, reset it, and start up the car, if the SES doesnt come on, you are good to go.

 

[GTP4ME]

SYP - I have a scanner and I did reset the ses but when scanning after replacing the bent up plug it still shows misfires with the 3 & 4 cylinders. The misfires are not setting the ses light but show up on the scanner here and there. That is what is leading me to believe that it is the coil pack since the cylinders share the same one.

Thanks,

Jamie

 

[EmersonHart13]

Have time to swap coil packs? You can see if it follows the pack or if it stays on the cylinders...

John

 

[Mike K]

Jamie, smashed electrodes are never a good sign. The misfire might be an indication of an internal mechanical failure. How do you 02's at WOT look? I realize that's an odd question but I'm going somewhere with it.

 

[GTP4ME]

Mike, I scanned my car and the o2's at wot are fine... In the 935-950 range. I think because I got on it while misfiring it caused that. It runs normal now but still shows on the scanner that 3 & 4 are sporadically misfiring. I will switch the coil pack tomorrow and see if it goes to the other cylinders though.

Thanks

 

[Fish]

Also, dont know if you have tried this, but make sure your wires are connected to your plugs and to the coils securely. I had multiple misfires cause one wire wasnt on the plug all the way and the other wasnt on the coil all the way.

Sometimes its the little things that make us think somethings wrong. (and sometimes thats all we hope thats wrong.) :lolsign:

 

[GTP4ME]

That is the first thin I checked and then I checked the plugs. I've made that mistake before and Mike could attest to that. I'll let you know what happens after I change the coils out tomorrow.

Thanks for your input Fish, it could be something as simple as that but this time I think it might not be.

 

[sweetness]

if you didnt put di-electric grease on the plugs you may have cracked the plug. I did this for about 4 weeks before I figured out what i was doing wrong.

If its the coils then swapping them will result in the misfires moving to the new cylinders. If thats what is happening then you will know immediately what the problem is. if that doesnt work try replacing all the plugs and put di-electric grease all over the ceramic part of the plug, and a good sized dab in the wire boot.


BC

 

[CoolGTX]

99% of smashed plugs mean a piece of piston had broken off at one time.

 

[Mike K]

Originally posted by CoolGTX@Dec 18 2004, 03:16 AM
99% of smashed plugs mean a piece of piston had broken off at one time.

[snapback]64616[/snapback]​

That's what I was getting to.

 

[GTP4ME]

I changed all the plugs and it seems to run fine now and there are no misfires. I don't hear any unusual sounds either. What is the clearance between the end of the plug and the top of the piston? Is it possible that under high rpm's and a misfire that the piston just tapped the electrode? I was thinking of getting a cam and heads in the next month or so. I guess I will find out then if there is any piston pieces floating around in there then.... Originally I thought the misfires were coming from the same coil but I was mistaken.

Thanks,

Jamie