2011 LR4 Misfire/rough idle

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scott schmerge

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She’s done and runs great. It took me a bit longer than 5 hours with the cleaning of the engine. I also cleaned a lot of the plastic bits and some of the engine bay. Not a bad job at all. I bet I could cut my time significantly the next time I did this.

one note, if you have a gap tool, there is a fuel prime option under pcm. I used that program and she stuttered for a second then came to life.
 

scott schmerge

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This is unexpected. Usually get about 16-17 average around town and this shows a marked improvement. No adaptation reset yet.
01A427CB-7240-4F6F-9C21-ECA2E96F1865.jpeg
 

scott schmerge

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Just did a 350mile round trip to Asheville. She’s never run so smoothly since I’ve owned her! Averaging (according to the computer) about 20-21 mpg on highway. That’s considerably better than what I was averaging. Love this truck more and more.
 

Kevintjones

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I have been following this thread because I am experiencing a lot of the same symptoms. However, I am getting misfire codes in cylinders 1,2,3,4. That seems weird to me since they are in different banks. I have a rough idle and sometimes I get the "restricted performance" warning (which always goes away if I restart the engine). I have replaced the spark plugs with no change. Any suggestions?
 

scott schmerge

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I have been following this thread because I am experiencing a lot of the same symptoms. However, I am getting misfire codes in cylinders 1,2,3,4. That seems weird to me since they are in different banks. I have a rough idle and sometimes I get the "restricted performance" warning (which always goes away if I restart the engine). I have replaced the spark plugs with no change. Any suggestions?

not sure! Have you tried injector cleaner? Is it a intermittent issue or constant? Mine would misfire immediately on start up.

does it run fine and then misfire? Are you getting a random misfire code?

I’m guessing more along the lines of coil packs or a high pressure fuel pump starting to fail (if intermittent). If coil packs, moving them to different cylinders would give you a more clear direction. But really don’t know.

You may also have gotten bad gas. Did it start shortly after fill-up? I’ve heard a purging of the fuel lines was successful in this case and also helped to clean injectors.

Sorry can’t be more help.
 

avslash

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I have been following this thread because I am experiencing a lot of the same symptoms. However, I am getting misfire codes in cylinders 1,2,3,4. That seems weird to me since they are in different banks. I have a rough idle and sometimes I get the "restricted performance" warning (which always goes away if I restart the engine). I have replaced the spark plugs with no change. Any suggestions?

If it is on both banks, I would start by looking at the HPFP and the low fuel pressure sensor that gets brought up in these thread from time to time.

 

Kevintjones

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not sure! Have you tried injector cleaner? Is it a intermittent issue or constant? Mine would misfire immediately on start up.

does it run fine and then misfire? Are you getting a random misfire code?

I’m guessing more along the lines of coil packs or a high pressure fuel pump starting to fail (if intermittent). If coil packs, moving them to different cylinders would give you a more clear direction. But really don’t know.

You may also have gotten bad gas. Did it start shortly after fill-up? I’ve heard a purging of the fuel lines was successful in this case and also helped to clean injectors.

Sorry can’t be more help.
No worries. I should have done a better job explaining it. I have had the vehicle for a year and it has always "shuttered" when idling. My CEL would come on when I used anything other than premium fuel which always surprised me, but I never worried much about it. I would use seafoam every few months. A month or two ago I started getting more regular codes and misfires. The misfires seem to happen on startup, but the car still runs good after startup.
I do get the random misfire code. I have moved the coil packs around and can't tell that it changes much. I think this problem is more than bad gas, but I am interested to look into it possibly being the high pressure fuel pump. Thanks again.
 

scott schmerge

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No worries. I should have done a better job explaining it. I have had the vehicle for a year and it has always "shuttered" when idling. My CEL would come on when I used anything other than premium fuel which always surprised me, but I never worried much about it. I would use seafoam every few months. A month or two ago I started getting more regular codes and misfires. The misfires seem to happen on startup, but the car still runs good after startup.
I do get the random misfire code. I have moved the coil packs around and can't tell that it changes much. I think this problem is more than bad gas, but I am interested to look into it possibly being the high pressure fuel pump. Thanks again.

how many miles on it?
 

scott schmerge

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115,000. It has not had the timing tensioners replaced that I know of, but it doesn’t sound like they are bad.

I would not think this is timing related.

115k, I’d start with the HPFP as it sounds more intermittent. But It could be unrelated. I’m glad @avslash also suspected the hpfp as that gives me more confidence.

as I’m also hearing more, it could potentially be your low pressure side too.

I’m running more with fuel delivery, but again not certain.

If you have a gap tool, I’d guess there are live values for the fuel pressures and you might see anomalies in fuel pressures while it’s misfiring which could help you diagnose the potential source.

I’m a bit out of my depth on using live values- but Patrick at Gap is really helpful. If you give him your symptoms and codes, he might be able to help you understand what live values to pull in order to drill down.

I’d also note that you’re probably due for new injectors, might be worth doing also as a maintenance item.

has the truck ever had crossover pipe/water pump etc? Has it been overheated ever?
 
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