Misfire! Misfire!

[KHoffRunner]

Truck was running great until I got about 5 miles from the house and it started misfiring bad and shuddering below 2k rpms. I just drove truck across country a month ago and it ran awesome. I was headed hunting and just took it easy the rest of the way and back. CEL comes on.. good I can pull the codes. I already grabbed new plugs on the way home. Pulled codes and it was both P0304 and P0306 misfire in cylinder 4 and 6. Threw the new plugs in, cleared the codes and it’s still misfiring. My number 6 plug was burnt up pretty bad, the rest looked decent.

I’ve search all the forums and no one has had two misfires on the same side out they never updated the thread on the solution. I figured I’d start this thread as material on our trucks is slowing down these days.

I changed my timing belt after a tensioner bolt backed out and shredded a fairly new belt last year. Could my timing have jumped?

I’m gonna try new wires tonight. I just want to avoid the plug and play of several hundred dollars of coils and injectors if I can. I’ll update the thread if I find a solution.

 

[Captsolo]

Call in a good mechanic for diagnosis

 

[Bad Luck]

Truck was running great until I got about 5 miles from the house and it started misfiring bad and shuddering below 2k rpms. I just drove truck across country a month ago and it ran awesome. I was headed hunting and just took it easy the rest of the way and back. CEL comes on.. good I can pull the codes. I already grabbed new plugs on the way home. Pulled codes and it was both P0304 and P0306 misfire in cylinder 4 and 6. Threw the new plugs in, cleared the codes and it’s still misfiring. My number 6 plug was burnt up pretty bad, the rest looked decent.

I’ve search all the forums and no one has had two misfires on the same side out they never updated the thread on the solution. I figured I’d start this thread as material on our trucks is slowing down these days.

I changed my timing belt after a tensioner bolt backed out and shredded a fairly new belt last year. Could my timing have jumped?

I’m gonna try new wires tonight. I just want to avoid the plug and play of several hundred dollars of coils and injectors if I can. I’ll update the thread if I find a solution.

If timing had jumped you would have misfires on at least one entire bank (2,4,6 or 1,3,5) or on all cylinders so I don't think timing is your issue. Plugs and wires is where I would start.

 

[KHoffRunner]

If timing had jumped you would have misfires on at least one entire bank (2,4,6 or 1,3,5) or on all cylinders so I don't think timing is your issue. Plugs and wires is where I would start.

Sounds good thanks. Glad it sounds like timing is still good, I’m trying to retire from doing that again. I’ll try new wires today.

 

[jgue467]

Just in case:
plug wiring diagram

Coils? They can be tested or in your case swap the green one with one of the others and see if anything changes. Luck.

 

[gamefreakgc]

Cylinder 4 and Cylinder 6 both going out at the same time I think would rule out a coil pack as that would mean Cylinders 1 and 3 would also go bad. When you said your plug look "burnt" what do you mean? That plug can tell you a lot on what happened. Was it covered in dry black soot, brown/orange with melted ground strap, wet, oily, etc.?

Cylinder 6 is the most common cylinder to have a head gasket failure as well. The small gap between 4 and 6 is the weakest point. Would cause massive compression loss and a compression test would be a definitive test. Check your coolant levels too.

 

[KHoffRunner]

Cylinder 4 and Cylinder 6 both going out at the same time I think would rule out a coil pack as that would mean Cylinders 1 and 3 would also go bad. When you said your plug look "burnt" what do you mean? That plug can tell you a lot on what happened. Was it covered in dry black soot, brown/orange with melted ground strap, wet, oily, etc.?

Cylinder 6 is the most common cylinder to have a head gasket failure as well. The small gap between 4 and 6 is the weakest point. Would cause massive compression loss and a compression test would be a definitive test. Check your coolant levels too.

The cylinder 6 spark plug was black, heavily covered in dry soot. Coolant looks fine, oil looks fine, so I’m hoping it’s not the hg.

On my way to get new wires now.

 

[KHoffRunner]

Wires did the trick! She’s purring like a kitten again, just in time for deer camp.

For future reference, I had two cylinders misfiring on the same side. Changed plugs and it didn’t fix it. Changed 5 yr old NGK wires with new and the misfires are gone. In the process I also flipped the one certain good coil pack to see if it the issue moved. Obviously that did nothing as it was a wire issue.

 

[Vintagexhd]

Let me know what you find out. I have had my 4 Runner for less than a month and ran and drove great until now. Got Cylinder 4 only misfire codes so i did all 6 plugs and the ignition coil in cylinder 2 since they are connected i believe. Still misfiring. Not getting any white smoke or weird coolant issues so im thinking (hoping) its not a HG or crack. I do get a pretty strong smell of unburnt fuel though. I dont have a scanner at my house to be able to constantly read codes to find if ignition coils or wires affect what cylinder misfire. I don’t have a way to do a compression test at home either. At this point I’m about to just take it to my mechanic, just figured I knock out the obvious before going to him. I may do ignition coil wires tonight, but if not it’ll be in the shop tomorrow. Hoping that what it is. Keep me updated on what you find out.

 

[Vintagexhd]

Wires did the trick! She’s purring like a kitten again, just in time for deer camp.

For future reference, I had two cylinders misfiring on the same side. Changed plugs and it didn’t fix it. Changed 5 yr old NGK with new and the misfires are gone. In the process I also flipped the one certain good coil pack to see if it the issue moved. Obvious that did nothing as it was a wire issue.

Literally posting my response as you post this. I may just do wires real quick. Took me like 2 hours to do the other work these things are way easier to work on than my M3... thanks for the update too, gives me hope.

 

[thegipper]

My buddies Sequoia (2UZFE) had a bad misfire (CEL) on Cylinder 3 and 6. It turns out it was only one bad coil that was causing the misfire but for whatever reason, it detected a misfire on multiple cylinders. We swapped around coils after changing plugs which didn't fix it. Once we moved the #3 coil the code followed it to its new location (#8) and cylinder 6 was no longer misfiring.

Not sure why that is because I'm also not sure how the computer detects the misfire (knock sensor?). He replaced that coil and has been driving for weeks now with no issues.

Just something to keep in mind. Glad you got yours fixed with something simple and cheap like wires.

 

[thegipper]

Let me know what you find out. I have had my 4 Runner for less than a month and ran and drove great until now. Got Cylinder 4 only misfire codes so i did all 6 plugs and the ignition coil in cylinder 2 since they are connected i believe. Still misfiring. Not getting any white smoke or weird coolant issues so im thinking (hoping) its not a HG or crack. I do get a pretty strong smell of unburnt fuel though. I dont have a scanner at my house to be able to constantly read codes to find if ignition coils or wires affect what cylinder misfire. I don’t have a way to do a compression test at home either. At this point I’m about to just take it to my mechanic, just figured I knock out the obvious before going to him. I may do ignition coil wires tonight, but if not it’ll be in the shop tomorrow. Hoping that what it is. Keep me updated on what you find out.

You could have a bad injector also. A leaking or faulty injector will cause a misfire, foul the plug and explain your gas smell in the exhaust.

 

[gamefreakgc]

That was probably the best case scenario fix. As you figured out, black soot indicates a rich condition which in this case was from a weak spark. I guess 5 years is too long for NGK wires then? Odd since I've been using them for a long time on several of my vehicles. I suppose there's always a chance of bad set.

 

[HiLife]

Time is an issue with misfires. A friend I helped with his misfire, fried his catalytic converter (p0420) on his 06 Corolla after driving too long on a misfire. His turned out to be a bad coil pack which fixed his misfire but was looking at a new Cat to fix the p0420 after a new denso o2 upsteam and downstream sensor didn't fix the p0420.