Looking for an advice about the best course of action here.

I bought 2012 QX56 with 107k miles a month ago. Less than 500 miles later one morning a few seconds after pulling out of the parking spot it started shaking , "check engine soon" light came on as I drove through the parking lot. I read P0300 ("multiple misfires") with my OBD sensor. It could drive on a parking lot, but car was shaking (even in N and P) and there was certainly not enough power. I didn't take it on a road that day.

It sat for a few days. On a weekend I reset the error code, tried starting and stopping it a few times - and suddenly it was working fine again - idling quietly without any vibrations and with normal power. I drove it lightly for a week (another 50 miles) not trusting it to get on a highway. One day, just as I pulled out from a parking spot in the morning it started shuddering and shaking again and "check engine soon" came on. At this point it wouldn't rev up above 1.5k bouncing back.

I brought it to a Nissan dealer in my town. They read "codes for intake valve timing solenoids bank 1 and 2" and "using data monitor found readings are at 69 degrees and should only be at 0-5 degrees at idle". They suggested timing is off and quoted $1.8k to remove the timing cover to verify.

I towed the vehicle from Nissan dealer to Infiniti dealer where I knew the vehicle was serviced before. They diagnosed "DTC for P0011 P0021 INT/V BANK 1 and 2 as well as P0300" and "found high pressure fuel pump lift valve damage due to high pressure fuel pump not working properly". On the phone their technician explained what he visually saw after taking the HPFP out: HPFP lifter has a hole in it; lifter scored the walls of the timing chain cover where it floats; and HPFP cam lobe isn't egg-shaped anymore after lifter seizing and pushing on it.

Infiniti dealer wants $7k to replace HPFP, lifter, and cam - which would require taking the timing cover off.

I imagine it must be very similar to https://www.facebook.com/a1stratemobile ... 593704661/ where one of the mods of this forum commented about seeing multiple owners reporting similar problem.

My questions for the community are:

- should I pay Infiniti to do these repairs or is it widespread enough issue where Infiniti may admit it's a manufacturing defect?
- if I only replace the lifter and the pump (which will be much cheaper than $7k because timing cover doesn't need to come off) - how long should I expect the fix to last, assuming the cam's lobe and lifter's "pocket" in the timing chain cover are scored?
- with QX56, how different the pump and lifter replacement procedure is from what's described in howto-m56-q70-5-6-vk56vd-high-pressure- ... 25231.html ?
- anything else I should seriously consider replacing at this point, given potential secondary damage done by disintegrating lifter?

Thank you!

An update: Infiniti dealer lied to me. I took the car to a local mechanic and we pulled HPFP and the lifter. Lifter was slightly worn (not perfectly flat). It did not have a whole in it which the dealer "saw with his own eyes". You couldn't tell the difference between the new and old lifters unless you touched it and felt a slightly concave surface.

We still got the lifter and the pump replaced as I had both new components purchased already. The problem persisted. Then we decided to add more gas - it fixed the issue. Apparently, either the in-tank pump is weak or fuel level indicator is faulty - but with a gas full of tank the car is driving perfectly now (I am writing this 2+ weeks after adding gas and driving it every day).

That's crazy man, now a month later, how is it running with the HPFP and lifter replaced?

unfortunately, having experienced this myself at about 140k miles and fixing it myself 3x, I finally had to have the dealer replace the hpfp lifter (for 4th time), follower cam, and timing cover, once you get the bad behavior and codes it's too late. The lifter has scored the follower cam such that each new lifter you put in wears even faster.

I got ~1500 miles out of first replacement lifter, 850 out of the 2nd, and 90 miles out of the 3rd. Note that it's very uncommon for the hpfp to need replacing even with lifter failure. It's a high price item though, so shops love to add that to the bill anyway.

Had this issue with my 2013 QX56 with 148K miles. Check engine light with codes P0087 and P0090. Took it to a local shop and they found that the high pressure filter had warn a hole in the center and they were able to pull the warn part from the cam housing. They had me stop by the shop to show me the damaged part and from what I could see the cam shaft did have minor scoring. The shop replaced the high pressure filter but did advise me that the cost to replace the cam would be excessive, but would need to be replaced in the near future. In the interim my wife came home today to tell me the check engine light came on today. I'm getting code P0011, which indicates cam shaft issue. Is it likely the high pressure failed this quickly?

Correction: High Pressure Fuel "LIFTER"! Damn spell check.

Going through this process now on a 2012 with 160k, I replaced virtually everything on the front of the engine including timing chains, timing chain oil jets, sprockets, tensioning items and oil pump, water pump, timing chain cover, and of course the high pressure fuel pump cam itself and lifter. It a 4WD so front axle removed along with the rack and pinion and oil pan. Most difficult job I have ever done.


My question is this, why did the bucket fail ultimately? It has to be a lubricant (ie lack there of) problem but literally I found no item that I could say was the cause of the problem.

It all started with the “low high-pressure fuel” code, found a hole in my lifter bucket but what I could see of the camshaft was perfectly fine, slick and polished. So I rolled the dice and put in a new bucket with assembly lube liberally applied and for one week it ran perfectly…. Then it didn’t, another hole which like the first time it affected the stroke of the high pressure fuel pump. The result is low fuel pressure and extremely low power. Anyone found that replacing these parts have been successful at long term reliability?

The buckets in the QX/Armada and the M56 are a little different, but the problem with both is usually the passages in the cover gumming up or a cover o-ring springing a leak. The passages are very tiny, and the bucket is the last man on the totem pole in the lubrication scheme. The slightest leak or restriction in the supply to the IVT solenoids leaves the IVT's monopolizing the oil and starving the pump bucket. On the M's there's a direct passage that can be accessed and blown out by removing the pump, but not on the other VK engines.