I was having a intermittent P0301 on a 2010 LR4 V8 with 161,500 miles. Then yesterday when I was accelerating onto the freeway, I got "performance restricted". It seems like it could only be two things: spark plugs or ignition coils (more likely than fuel injectors). I replaced the spark plugs about a year ago, so I didn't figure it was those. The ignition coils were original FoMoCo Bosch. Before you tell me that there's an easy test just to swap the coil, the problem was intermittent, so who knows when it was going to happen again. So I decided to replace the ignition coils.

I know that this is probably frowned upon, but I went with the A-Premium chinese brand on amazon ($100 for 8). I understand that these are not the same as Bosch and Delphi, but I also can see at Rockauto that there are like 8 different brands ranging from $15-47 each, and I also know from my international business experience that the majority of these are made in China anyway and there are probably only 2-3 factories that actually manufacture these for different brands. Additionally, I have used A-Premium products in the past (including the spark plugs) and they seem to be good enough. I don't need my LR to go another 161,500 miles, so if I get 50,000 miles I'll be happy.

The replacement is fairly straight-forward. Remove the air boxes and battery boxes, remove the heat shields. So then I fired it up and it ran really rough!! 3 misfires P0301, P0303, and P0306! WTF?!? So the only potential problem would be with seating the coil or the connector, so I redid the procedure on cylinder's 1, 3, and 6, then restarted the truck and... No codes! It's still pretty early, but I did about 25 miles on it, including some fast accelerations and everything seems to be running very smoothly.

If I have problems with the A-Premium coils then I'll report back ASAP.

 

Today I started the truck and got P0301, P0303 and P0304. It seems to happen at start up because I got P0316 as well. So perhaps a fuel issue?

 

You have 4 cylinders misfiring. Not all of them.
Its not clear to me if the codes existed before you changed the components.
It's also not clear to me which vehicle you actually have therefore, which engine are we talking about...
Common root causes for the P0300s includes coils, plugs, injectors, fuel...
Using OE would simplify getting to baseline.

 

Thanks for the reply. This is on a 2010 LR4 V8.

I got the scanner out and the fuel pressure is dropping significantly after turning off the car. With the car running the high pressure fuel pressure jumps to 2100 PSI (which I believe is spec) and then settles on 450 and then rises and falls as I step on the gas. So I don't think it's a fuel delivery problem. When I shut off the truck, the pressure drops quickly so I'll need to do another read when the car sits overnight, but I'm now guessing leaky injectors are the problem.

I also drove it hard on the freeway and it performed well, until it didn't. It threw a P0303 and went into "performance restricted" mode.

 

I let the car sit overnight and then measured the fuel pressure. It was at 50 PSI (which is spec for the low-pressure pump). To compare, I measured my 2016 Range Rover at it was at 1150 PSI after sitting overnight. So I've confirmed I'm losing fuel pressure while the car sits. Still leaning towards a leaky injector, but will talk to my master mechanic friend before starting any work.

 

I see the title has been changed. Yes, as misfires are occurring on all cylinders, fuel pressure was probably the culprit.
Or all of the discount parts ;-)

 

The title was to help other people potentially find support for those codes (as they didn't exist in the forum). I'm only having issues with 301, 303, 304 (and 300 and 316).

 

I have the truck "running on all cylinders" again! At least for now.

I had 3 misfires. One I changed the spark plug then reseated the ignition coil and it worked. The others I changed 2 injectors (using the original Bosch) and 2 spark plugs (also Bosch) and now they both work as well. No more codes!