Looking for advice on misfire

[brentagade]

Greetings,

Which forum would be the correct place to ask troubleshooting questions for misfiring? Here or Engines?

Thanks
Brent

 

[JExpedition07]

Greetings,

Which forum would be the correct place to ask troubleshooting questions for misfiring? Here or Engines?

Thanks
Brent

Ask away, we’d be happy to help. Have any codes been pulled and do you know which cylinder is having the misfire?

 

[1955moose]

Here your better off, because unless you go through the other parts of the website, 1st, 2nd, 3rd edition general problems pop up under my timeline. Any hoo, please state year, engine size, model, and finally 2 or 4 wheel drive. Then we can narrow down the idiosyncrasies of each year, and model. Also if you've run dtc codes diagnostic, it gives us a jumping off point! Please post those.

Sent from my N9131 using Tapatalk

 

[JExpedition07]

He’s got a 2012 EL XLT 5.4L, now we wait to here back in if he pulled codes and if he knows which cylinder had the misfire. I’d start by switching a coil over and see if your misfire condition moves to another cylinder. Most common causes of misfires on these engines are a faulty ignition coil or bad boot.

 

[brentagade]

Thanks!

I have a 2012 XLT EL, 5.4 3V, with about 101k miles. It's been running like a top up until about a month ago. It started running rough and eventually began misfiring. I used to have a 2002 F150, so in my experience it was a bad ignition coil. I got the code read to find out which one and it returned 0430 steering me toward possibly O2 sensors or Cat.

As I was contemplating what to do I went and got the oil changed and had them read the code again. This time it returned additional codes of 0300 and 0307: Random misfire and #7. That helped me narrow it down (I thought) and would fix the 0430 code possibly too. Because of the mileage, I was just going to do all the plugs and ignition coils myself. I spoke with 5 different people/mechanics and they all gave me the horror story of 2 piece plugs and to not change them myself. So I took it to the stealership and let them rake me over the coals to swap out all the plugs. Of course they always come back with more, but I wasn't prepared to sacrifice my first born for new ignition coils at this time so just paid for the plugs. They said Bank 2 cylinders were showing between 1-3% compression change.

I went to Autozone, got a whole set of Duralast coils and changed them in 20 minutes. The truck ran fine for about 2 miles and began missing again. "Son of a .....". So I got the codes read again. This time 0430, 0300, and 0306....#6....WTF? So I thought, maybe I got a defective coil in the set of 8. I went back to Autozone and used the warranty to swap it out. Ran "ok" on the way home. Next morning, missing again on the way to work. Ugh.... Soooo...I've had new plugs replaced by the stealership and all new ignition coils and still misfiring. I'm stumped. Could this possibly be an electrical issue with the wiring and signal??? Please help.

Thank you much.

 

[JExpedition07]

Did the dealer or you change out the boots by any chance? Also those mechanics you talked to didn’t have a clue what they were speaking of, a 2012 expy didn’t have 2 piece plugs or any of the problems related, that was resolved long ago. If the boots are old one may be allowing spark to escape and arc. I would replace the boots on the cylinders in question see if anything changes, Here is a great read.

http://troubleshootmyvehicle.com/ford/4.6L-5.4L/how-to-diagnose-misfire-codes-1

 

[brentagade]

What are "boots"?

Imagine that...way for them to make more money I guess...convince someone otherwise.

 

[JExpedition07]

What are "boots"?

Imagine that...way for them to make more money I guess...convince someone otherwise.

Blue items shown here, from the coil and over the plug, if one cracks or is just worn out spark will arc and take two paths.

 

[brentagade]

The dealer replaced the plugs...I replaced the ignition coils. So then it would be a yes because it's all one piece...well attached together...

https://www.autozone.com/ignition-t...-multi-pack-ignition-coil/591230_520521_17367

 

[brentagade]

Thanks for that article too. Good information.

So considering code 0430....could O2 sensors or a bad catalytic converter cause misfires?

The dealership did say something about bank 2 not acting right...which is on the same side as the code was giving. I was thinking anything involving exhaust would be a separate issue....maybe not??

 

[JExpedition07]

I don’t think you have a catalytic converter issue, very unlikely. Yes an 02 Sensor can cause misfires since they tell the engine how to burn the mixture and contributes to controlling timing, a bad 02 Sensor may cause the random misfire code your getting possibly. The fact that the issue temporarily rectified when new coils were applied leads me to believe it’s electrical, But I could be incorrect.

 

[JExpedition07]

But your P0340 does suggest 02 sensors. Cat is always possible but with the low mileage I’m thinking an 02 is more likely. Probably want to test those.

 

[bobmbx]

I don’t think you have a catalytic converter issue, very unlikely. Yes an 02 Sensor can cause misfires since they tell the engine how to burn the mixture and contributes to controlling timing, a bad 02 Sensor may cause the random misfire code your getting possibly. The fact that the issue temporarily rectified when new coils were applied leads me to believe it’s electrical, But I could be incorrect.

There are 3 things that can cause a misfire: 1) Fuel...either too much or not enough 2) air....not enough in the cylinder and 3) lack of spark.

Since the misfire is not on all cylinders, we can rule out air for now. We can have confidence in spark due to the new coils and plugs. It could be the injector is clogged or failing intermittently.

Try a can of Gumout or Seafoam in the fuel.

 

[JExpedition07]

There are 3 things that can cause a misfire: 1) Fuel...either too much or not enough 2) air....not enough in the cylinder and 3) lack of spark.

Since the misfire is not on all cylinders, we can rule out air for now. We can have confidence in spark due to the new coils and plugs. It could be the injector is clogged or failing intermittently.

Try a can of Gumout or Seafoam in the fuel.

We still can’t have confidence in spark we don’t know the condition of boots, connectors, or wires. The issue of the catalyst system code could be a symptom of the misfire, tough thing to diagnose.

 

[bobmbx]

But since you are getting PO


We still can’t have confidence in spark we don’t know the condition of boots, connectors, or wires.

True. But, except for the boots, those are less likely causes.

 

[JExpedition07]

True. But, except for the boots, those are less likely causes.

Fuel Injector connectors are famous for going bad too... I agree on the gum out in case the injector is clogged.

 

[david_jr]

Another thing to consider is plugs break when installed, even by the dealer. I know because it happened to me and yes it did result in a misfire. Overall misfire diagnosis will make your hair (if you've got any left) hurt!

 

[brentagade]

So after driving back and forth to work today I checked the codes again when I got home. An additional code was added, 307 for Cylinder 7. So it's not just the one cylinder...

 

[JExpedition07]

at this point it’s safe to rule out plugs, boots, coils IMO. I’d replace the bank 2 02 Sensor downstream. Could be fuel too, possibly stuck injectors or pressure problem to the rail since your getting multiple random misfires. My advice would be injector cleaner and 02 Sensor.

 

[deweysmith]

Pre-cat O2 sensors aren't hard to get to but hard to change. I had to get the threads (on the pipe side) boiling lava red hot and then spray them with water gently to cool them off a bit and then they popped right out.

When I say I, I mean my brother-in-law. He owns a muffler shop, told me that's his trick, and it almost never fails. I got the right side one out on my own with a breaker bar but it's nigh unto impossible to get a breaker bar on the left one and get any leverage with the 4x4 in the way, so I took it to him. Took him all of 5 minutes.

The wire looms are a pain too, they live right between the exhaust and the transmission which are both HOT. Would not recommend in the driveway but if you can get a lift it's doable on your own.

The post-cat sensors don't adjust mix at all, so they wouldn't typically cause a misfire IMO. They just make sure the catalyst is doing its job.