Misfiring Cyl 2/4/6 ?? 2015 LR4

Salanizi

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Not sure what an emptied out cat would do. I assume that would increase exhaust flow, which is the opposite of what I was thinking. But how/why would a thief carefully disassemble the cat, empty it out, and put it back together installed on the car? That just doesn’t make much sense to me. Here people steel cats all the time, but they just cut them off and take the whole thing.

Did the exhaust specialist give you some reason they think the cat has been emptied? Did they do some sort of diagnostic? Usually they look at temp or backpressure at least.

I’d drive it for a while - maybe 50 miles or so - now that you replaced that last o2 sensor and the fuel trims improved. The engine will learn new adaptations and might sort out the rough idle.

Ok so it was a 4 hour job...

Cats have not been emptied, and dont really appear clogged

Once they were dissassembled he poured 1.5 bottles of liqui moly cat cleaner (the type you should connect to the air intake) in each cat and let them sit for 30 mins (he turned them over half time) and reassembled.

Interesting to note that they appeared to have been dissassembled before (bolts were a cocktail) and the right side cat was a bit loose (leaking maybe?)

It smoked like crazy for 15 mins when the car was started

I also poured a bottle of liqui moly cat cleaner (the type that goes into the fuel tank) and half filled the tank.

Lets see if it fixes things
 

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Salanizi

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There was a noticeable difference in the idling and also acceleration after using the liqui moly catalyst cleaner, so I decided to buy two more bottles today and applied them correctly through the throttle body.

Car idles smoother now although no where as smooth as my 2010 XK 5.0, and the hesistation on reverse is still there
 

jlglr4

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Poured through the throttle body, it might also have the effect of cleaning up the throttle body itself and the intake valves (prob not much, but maybe a little). Have you tried actually cleaning the throttle body? If the butterfly valve is sticking, that can give you a rough idle. You also could try an intake cleaner to hit the valves better. Carbon build up on valves also can cause rough idle.
 

Salanizi

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Poured through the throttle body, it might also have the effect of cleaning up the throttle body itself and the intake valves (prob not much, but maybe a little). Have you tried actually cleaning the throttle body? If the butterfly valve is sticking, that can give you a rough idle. You also could try an intake cleaner to hit the valves better. Carbon build up on valves also can cause rough idle.

I cleaned up the butterfly valves myself last week, they look brand new (they were quite clean to begin with)

Indeed the liqui moly product goes through the intake and clean the intake valve as well, i believe it has done a great job at that

My next step is to replace all 6 injectors With new Bosch ones, is it worth doing?
 

jlglr4

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Just so we’re on the same page, it’s not the valve itself that gets dirty, but the surrounding tube that it sits in. A small amount of gunk builds up right where the edge of the valve meets the throttle body tube, causing it not to close all the way or to stick just a bit when it tries to open. To clean it you need to hold it open (carefully - it can be damaged) and clean the tube it sits in with carb cleaner.

As for the intake valves, you cannot see them with the supercharger/intake manifold on the car, so not sure how you can tell if it worked or not.

Regarding injectors, its a pretty expensive undertaking (at least here in the states). I’m not the type to just replace things. I’d much sooner sink some money into a gap iid tool and really try to figure out what the problem is. If your fuel trims are looking normal now, not sure why the injectors would need to be replaced (or why there is still a misfire or CEL for that matter). Misfires are fuel, air, spark, compression, or timing. I’d be trying to figure out what’s at fault.

I read through your prior thread again, and you thought you had this sorted with new engine mounts (misfire wasn’t actually a misfire?). I take it the problem went away briefly and returned?
 

Salanizi

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Just so we’re on the same page, it’s not the valve itself that gets dirty, but the surrounding tube that it sits in. A small amount of gunk builds up right where the edge of the valve meets the throttle body tube, causing it not to close all the way or to stick just a bit when it tries to open. To clean it you need to hold it open (carefully - it can be damaged) and clean the tube it sits in with carb cleaner.

As for the intake valves, you cannot see them with the supercharger/intake manifold on the car, so not sure how you can tell if it worked or not.

Regarding injectors, its a pretty expensive undertaking (at least here in the states). I’m not the type to just replace things. I’d much sooner sink some money into a gap iid tool and really try to figure out what the problem is. If your fuel trims are looking normal now, not sure why the injectors would need to be replaced (or why there is still a misfire or CEL for that matter). Misfires are fuel, air, spark, compression, or timing. I’d be trying to figure out what’s at fault.

I read through your prior thread again, and you thought you had this sorted with new engine mounts (misfire wasn’t actually a misfire?). I take it the problem went away briefly and returned?

Engine mounts were replaced because there was a vibration on idle + a misfire which was happening due to an issue with the camshaft or vanos unit (cant really remember) (i ended up replacing all mounts/coils/sparks/air filters/complete cooling system + engine fan / 2 O2 sensors) + dumped four bottles of injector cleaner in the tank + replaced camshaft and retimed engine

Anyway that was fixed then, we got to two months ago when the car would shake and hesitate when i press the brakes, turns out all brake vacuum hoses were shot and had those replaced

That sorted it out for a month, then it started misfiring again (only on low RPM and when brakes+gas pressed together), and i started getting fuel pressure codes and misfire codes, which led me to replace all 3 fuel pumps high and low pressure and filter + 2 fuel pressure sensors high and low + 4 remaining O2 sensors (fixed the fuel trim) + 2 Maf sensors + new round of 6 spark plugs + thoroughly cleaned throttle body and cats

Now the car hasnt misfired for a week and is considerably faster when it comes to acceleration since i bought it, however there is still the rough idle and the occasional hesitation only when in reverse

Since i have paid around 85% of the purchase price of the vehicle on parts and repairs (btw i also replaced the aircon and complete suspension system with 3 solenoids and compressor) - my way of thinking is that only 2 items remain short of replacing the entire engine and the fact that i only have the rough idle left and hesitation when in reverse:

1. 6 new bosch injectors
2. 2 new engine mounts (these were replaced 6 months ago, but not on my watch and i suspect i got scammed with fake parts i cant really tell)

My mechanic says my issue is that with my rebuilt engine, the job was not done right and i have either a bad sleeve job or a wobbly crankshaft, and no amount of money will fix that short of an engine rebuild and better to replace the engine rather than rebuild it


What do you think?
 

greiswig

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What do I think? I think I wish I could be more helpful.
You've tried a LOT of different things. And it seems like you've made some really good progress.

If it were me, I would be asking the mechanic for more specifics on why he thinks the crankshaft or the sleeve job was faulty. You earlier said that the motor was replaced, but didn't mention that it was rebuilt. I'd want to know who did the rebuild, or was it actually replaced with a crate motor?

And I'd be asking myself what might the harm be to leaving things as-is - in effect, will this be liable to fail suddenly and catastrophically and in the next 10k miles, or would there likely be a slower degradation that might even help me figure out what was going on?

And, whether you keep this engine or get a new one, I'd invest in that GAP tool that people have been mentioning. It will be worth it in the long run if you plan to keep the truck.
 

Salanizi

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What do I think? I think I wish I could be more helpful.
You've tried a LOT of different things. And it seems like you've made some really good progress.

If it were me, I would be asking the mechanic for more specifics on why he thinks the crankshaft or the sleeve job was faulty. You earlier said that the motor was replaced, but didn't mention that it was rebuilt. I'd want to know who did the rebuild, or was it actually replaced with a crate motor?

And I'd be asking myself what might the harm be to leaving things as-is - in effect, will this be liable to fail suddenly and catastrophically and in the next 10k miles, or would there likely be a slower degradation that might even help me figure out what was going on?

And, whether you keep this engine or get a new one, I'd invest in that GAP tool that people have been mentioning. It will be worth it in the long run if you plan to keep the truck.


The motor in my car is a rebuilt one not a crate motor

I dont think i will keep the car for more than 18 more months since its not working properly...just waiting for MY2024 cars to hit showrooms
 

Salanizi

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I am starting to suspect ECT sensors now, could failed sensors cause this?
 

ftillier

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I feel you'd be well served getting an IID tool, so you can not just pull codes, but data log sensors live. It would make things more data driven rather than throwing parts at it and hoping they do the trick.
 

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