Good AM,

My name is Jason and I reside in Wake Forest, NC. While I'm a new member, I'm not new to referencing this site for valuable guidance. I'm creating this post out of frustration and desperation. Back towards the end of October, I purchased a '16 RR HSE from an independent dealer in SC. The main attraction was the color combination along with the fact that the long block was replaced at 87K miles (car has 109K). I was able to speak with the shop, that replaced the motor, which provided me with further confidence to make the purchase.

After the 5-hour drive from SC to NC, I experienced a couple issues on the way home. While fueling up, I encountered an issue with the gear shift being stuck. After shutting down/restarting, the issue never occurred again. Minutes from home, I noticed the engine light came on and the car started to stumble. I pulled over and shut it down. After a restart, no further issues. During the first week of ownership, the engine light would randomly come on when I would approach a stop sign or traffic light. Each time, I was never able to pull a code until the light eventually stayed on. At this time, I received a P0304 for a cylinder 4 misfire. At first glance, I noticed the ignition coil appeared new. I ended up purchasing a new ignition coil along with a spark plug. The issue persisted and I reached out to a local mechanic for guidance. He determined the fuel injector was inserted incorrectly which tore the gasket. The selling dealership agreed to cover the expense for a new injector. The mechanic noticed that all injectors, on the driver's side, had been inserted incorrectly. He removed the other two, cleaned, and inserted correctly. Unfortunately, this did not resolve the stumbling issue. After providing the selling dealership with this update, they requested to have it shipped back to SC for their local Land Rover mechanic to assess. The vehicle was shipped to SC the day after Thanksgiving.

After 2-months, I finally received the car back. The SC-based mechanic performed the following:

-Replaced ECM (reprogrammed pre-owned)
-Replaced radiator (2-year old radiator blew out on test drive)
-Replaced water pump (2-year old non-OEM water pump pulley failed *pretty certain a result of the coolant leaking)
-Replaced belts
-Replaced heater valve
-Replaced gear shift module

The stumbling issue appeared to be related to the ECM. My local mechanic was confident it was ECM-related as he read an article that the ECM programming could become corrupted when injectors are installed incorrectly. After the ECM was replaced, the stumbling issue never occurred again. The vehicle has been driven hundreds of miles without issue. Yesterday, I encountered the engine light coming on and the stumbling returned. This morning, I pulled the following codes:

-P0300 Random/Multiple Cylinder Misfire Detected
-P0304 Cylinder 4 Misfire Detected
-P1315 Misfire Persistent Fault
-P0305 Cylinder 5 Misfire Detected

The issue can be temporarily remedied by shutting the car down and restarting. This confirms my suspicions that the issue is electronic and not mechanical. I apologize for the long-winded thread but wanted to provide all the history. I am at a loss on what to do next. Is there anything else that can cause these multiple misfires? The local mechanic did perform a compression test and everything confirmed a new block. Could an O2 sensor cause these issues? Any guidance would be appreciated.

Thank you,

Jason

Following a brief test drive yesterday, I experienced no engine light or stumbling issues. As mentioned before, this issue is intermittent and the car has been driven hundreds of miles without issue. One thing I've been thinking about is the catalytic converters. The original engine was lost at 87K miles following a breakdown of the cooling system. Is it possible the driver's side catalytic converter was damaged during the time of the engine failure? Could a bad catalytic converter cause random misfires on the same bank?

Plugs, ignition coils, fuel injectors, and wiring have all been replaced or tested. I'm wondering if this is related to the catalytic converter getting too hot. When the issue occurred last week, the car was idling for an extended period of time. Perhaps when she's moving on the road it gets sufficient cooling to keep the catalytic converter from overheating.

Cylinders 4 and 5 are on opposite banks

It has been my understanding that cylinders 4, 5, & 6 are on the left side.

My apologies for some reason I assumed it was a 5.0 sc

Good AM. Yesterday, I conducted a back pressure test on the upstream 02 sensor port on bank 2. This confirmed there are no issues with the bank 2 catalytic converter. Since I removed this sensor, I am going to replace with a new one.

The latest behavior is that I get a blinking CEL/stumbling when the car gets warm and is idle or at very low speeds when approaching a stop sign or traffic light. The issue can be resolved by turning off the car and restarting. Typically, the issue will resurface when the engine remains hot during the above conditions. There are no issues when the car is driven at higher speeds nor when the engine is cold. When it does throw a code, it is a misfire in cylinder 4 or 5. On the 3.0 SC, these are both on bank 2.

This is everything that has been done:

-Cylinder 4 fuel injector, ignition coil, and plug are new
-Cylinder 5 and 6 injectors have been cleaned
-Cylinder 5 and 6 ignition coils have been tested
-Both MAF sensors have been cleaned
-ECM has been replaced
-Throttle body has been cleaned

The ECM is the only item that appeared to resolve the issue for an interim period. Following the ECM replacement, the car was driven several hundred miles with no CEL/stumbling.

Any ideas?

Could this be a fuel delivery issue? The issue starts when the engine gets warm and is idle or at a low speed. Never an issue on the highway and the issue can be resolved by a restart. Is there a component of the fuel delivery system that is impacted by heat and/or lower RPMs? Not sure if there is a dirty fuel filter, faulty fuel pump, or fuel pressure sensor.