2011 LR4 Misfire/rough idle

[TheDave]

2011 LR4 with 118k miles. Owned this truck since it had 18k miles, no previous engine problems.

I was driving to an appointment yesterday and was running late as well as was almost out of gas. Usually never get below 1/4 of a tank, but got the “low fuel” notification while en route, so i stopped and put half a tank in from a random gas station along my way. Would say I had about 15 miles until empty.

After my appointment, about 3-4 miles away from the gas station, I managed to get about 2 miles down the road and was sitting at a stoplight when the vehicle started vibrating abnormally. I look at the dash and see my RPMs fluctuating, check engine light comes on and starts flashing (misfire I presume from previous experience, as well as would explain the rough engine idle), “Reduced Performance” notification, as well as a slight smokey haze coming from the exhaust (smelling strongly of fuel). I pulled off the road and got the truck towed home. I’ve since started the truck a handful of times, but hesitant to let it run longer than 20-30 seconds because of the fuel smell from the exhaust. I noticed that the passenger side exhaust has a vaporized fuel appearance (doesn’t appear to be oil or water smoke, pretty confident it’s fuel) for a few seconds after shutting the truck off. Oil and coolant levels appear to be normal. The truck did not overheat.

I’m going to change the plugs out because they are beyond due. Also going to grab a code reader to get additional info since I don’t want to drive the truck to the parts store to get the codes. I’m considering a seafoam cleansing, but mostly want to get the codes first so I have a better idea of where to start a diagnosis.

I know running the tank that low was dumb and I’m kicking myself for it, hoping I didn’t do any damage. However, I’m thinking it could be bad fuel also. Could there be air in the fuel line? I know the codes will provide a bit more insight, but posting for now in case someone recognizes the symptoms.

 

[ktm525]

Could be bad gas . Start simple before getting crazy.

1) I would top up the tank with good fuel to dilute the potentially bad stuff
2) add some gas line antifreeze to mop up any water which may have come with the bad gas
3) change the plugs regardless you are due.
4) run a can of BG44K through it.

Hopefully that takes care of it before we start looking at bits and pieces and more $$.

You doing the plugs or a shop?

 

[cperez]

Is it a known risk factor to run a tank down low enough to trigger the Low Fuel lamp? I hope not. I don't make a habit of it but it's not a total rarity, either. I've never heard that it could potentially damage an engine, especially since you didn't run it dry (which might be a different matter). Hope the codes reveal something clear about the issue. Also reasonable advice from @ktm525...good luck and let us know.

 

[TheDave]

@ktm525, the advice is much appreciated. I’ll work down that list to start. I’m personally going to attempt the plugs. I’ve always worked on my previous vehicles, although this will be the first for this truck since it was under warranty up until 100k miles (aside from the usual wearables that were my responsibility). I’m about to do some research on which specific plugs to buy, but was thinking NGK iridium plugs sounded familiar for the LR4...

@cperez, from what I understand, running your fuel tank low can burn up the fuel pump if it runs dry. I’m not sure if running low on fuel qualifies into a burnt pump, but it’s definitely taking a risk from what I’ve read.

 

[ryanjl]

An old wives' tale cautions against running low on fuel because it makes the engine run on the sediment at the bottom of the fuel tank. This, of course, ignores the fact that the fuel pickup in a gas tank is always located at the bottom of the tank regardless of the fuel level.

 

[Mcb14230]

An old wives' tale cautions against running low on fuel because it makes the engine run on the sediment at the bottom of the fuel tank. This, of course, ignores the fact that the fuel pickup in a gas tank is always located at the bottom of the tank regardless of the fuel level.

To add to this it only hurts to run a vehicle completely empty. Diesels especially so.

 

[ryanjl]

To the OP's problem, bad gas seems like the Occam's Razor answer.

I have read that gunk in the throttle body can also cause a bad idle and fluctuation of RPMs. It's not a hard DIY job to clean that out.

 

[TheDave]

@ryanjl, it does seem the most likely culprit at the moment. I’ll check on the TB as well. I appreciate the advice.

 

[ktm525]

Here are my original passenger bank plugs at 100k miles. No idea why one plug had rusty threads. Some water ingress I guess? 6C10 no longer exists. I believe it is now 7C10 as per NGK

There is a great step by step DIY on spark plug replacement. It isn't easy as there is very limited space but if you take you time it can be done. Most shops here charge about $500 labour (Canadian) to do it. You will soon find out why. Yes NGK Iridiums are about $10 each and are the stock plug. NGK changed the plug number (superseded the original plug number.)

 

[BBLR3]

Dont do the forum thing very much anymore, but I've learned a lot about my LR4 from this forum, so pay it forward. Onto the OP's problem. I literally had this exact same issue earlier this year. Symptoms make it appear that its a spark/ignition issue. If you get a code reader, it would give you engine misfire type errors. But you probably have an fuel injector bank stuck wide open. This essentially blows the spark out, which results in all the fuel in the exhaust you are smelling. Since I didnt have any way to diagnose what I thought was an ignition issue, I ended up going the dealer route (savings account extended warranty program lol) for the fix. Hope this helps.