[njeltema]

I hope to do this soon, since I am having the same issues everyone else is having with their 2017. I am skilled enough, and competent enough, to do the repairs on my own. By that, I mean I can take things apart and put them back together with no problems. However, timing chains freak me out. Without access to any repair manuals, how do I ensure that the timing is still correct when I take the old chain off and put the new one on? As long as nothing rotates should I be good? From your write up it sounds like I can take it apart and put it back together without having to do anything but turn the car on when I'm done, is that correct?

 

[just_bob]

Excellent write-up Jason! Very helpful.

As you say there is very little good info on this engine online. To keep the information together, I'll add my experience here.

My 2017 Pathfinder would not start. VQ35DD engine. History was unknown. No spark and no fuel at the cylinders. 179,000 km on the odometer. By accident I found the engine ran after a very long crank when the bank 2 exh. cam position sensor was disconnected. The timing chain was very noisy.

I used a PicoScope to verify the crank to intake cams relationship. The results did not match the pattern shown for the VQ35DE Nissan field service manual. I checked a 2020 Pathfinder with the VQ35DD engine and it was similar to mine. The FSM for this DD version does NOT show cam/crank waveforms.

The sensors are fed +5volts and ground. The output is normally +5volts but goes to ground when a tooth or sprocket is encountered. The crank has 18 teeth, a gap of 2 teeth, 18 more teeth, another gap of 2, another 18 teeth and a final gap of 2. With the teeth 6 deg. apart, 18 teeth and a gap is 120 deg. Two more patterns are a full crank rotation. Two crank rotations are required for one cam rotation. So basically, 6 groups of 18 teeth with gaps for one complete combustion cycle.

The intake cams have 3 pulses per rotation. (120deg apart) Bank2 is 60 deg after bank1. The overall effect is that there are cam pulses from alternate cams every 120 crank degrees. They indicate an approximate TDC for each of the 6 cylinders.
(EDIT: Subsequent info shows the crank gap coincides with BDC. See later post.)

The good 2020 engine had the cam pulses aligned with the crank gaps. My engine had the bank 2 timing about 10 deg. early. I suspected the bank 2 intake cam phaser to be stuck in an advanced position. The timing cover needed to come off.

My Pathfinder was AWD and the original write-up was on an FWD. I wasn't sure removal out the top was possible so I opted for in-vehicle cover removal. It can be done. It's ugly and Nissan's FSM is not very accurate in this matter.

Once inside, I found the chain extremely loose and the bank 2 intake cam sprocket/timing chain marks off 1 tooth. Exactly what Jason had discovered and more. But on moving the cam slightly, the tensioner took up the slack immediately and looked normal and tight albeit one tooth off.

The problem ended up being the tensioner itself. There is a ratcheting mechanism that prevents the piston from retracting back into the bore once it has been extended. The teeth on the ratcheting pawl were worn off or broken. I could push the piston back in with only moderate thumb pressure. A new one is solid with no reverse movement whatsoever. I could have easily replaced the chain and guides, put it back together then have the same problem in the future.

 

[TejasMtnBiker]

You made it look pretty easy, the front coming off is a back saver I bet

 

[PoManzPathy]

That is an excellent diag and great information @just_bob.

This is alarming to me to hear of these issues with only 111K miles (179K kilometers) on the engine. I'm not sure maintenance alone will prevent this type of failure and shop costs to fix it (if you could even find one to do it) would be astronomical. To the point these vehicles will just be junked.

 

[just_bob]

Here are some screenshots of waveforms. This was sufficient for my purposes. However, you may notice there is not enough info to determine specific cylinder numbers. Typically, an extra pulse or something is needed to identify cylinder 1 TDC so the ECU can deal with the correct injector and spark at the correct times. If one needed to diagnose no starts or long cranks this additional info would be useful. If anyone has any insight on this, feel free to comment. The FSM wasn't helpful.
(Sorry for the poor quality of the screenshots. I couldn't find a better way of inserting the very clear PicoScope software images. But I think the basic info is there.)

 

[just_bob]

A question for Jason:
Would you happen to have the part number for the front cover lower seal? I was given part # 11121-7Y000. Unused it appears thicker than the used original and the online parts manuals say it works on both the DE and DD engines. I have my doubts.

Edit: 11121-7Y000 is CORRECT. Some Nissan online parts lists incorrectly have the front and rear upper pan seals reversed. (#11121-7Y010 is for the flywheel end and is 1/2 to 1 inch longer.)

 

[PoManzPathy]

Just to add to the above info, here's a cool video showing the timing marks on a 2017 VQ35DD along with showing the wear items that were replaced.

 

[just_bob]

At the very end of the video, he easily pushes the old tensioner piston back into the bore with little effort. That should NOT be possible!!! The ratcheting pawl is broken or worn out.

 

[just_bob]

Found this in the FSM showing the exhaust cam position pulses. The double pulses and pulse spacing would give the ECU enough info to determine where each cylinder is.

 

[Cdavid575]

Man if it weren’t for this post I wouldn’t have the confidence to do the project. Thanks for the info and all the pictures, I just started opening my wife’s car today. Same deal, chain slapping sound at idle and low rpm, cam position sensor is firing, it had sludge buildup throughout the engine, clogging up my valve covers and messing with my pcv system. These engines don’t seem to vent properly.

 

[PoManzPathy]

Man if it weren’t for this post I wouldn’t have the confidence to do the project. Thanks for the info and all the pictures, I just started opening my wife’s car today. Same deal, chain slapping sound at idle and low rpm, cam position sensor is firing, it had sludge buildup throughout the engine, clogging up my valve covers and messing with my pcv system. These engines don’t seem to vent properly.

What year and how many miles on it? Also.. for the sake of data collection, how often were oil changes done on it?

I hear you on these particular VQ35DD engines not venting properly, but they defy any logic I can come up with in terms of why they blacken and sludge the engine oil the way they do.

You figure with a bad PCV system, you get visible moisture build-up somewhere, like oily mayonnaise build-up on the fill cap, PCV plumbing or dipstick. You don't see any of that with these.

If it was fuel dilution, the oil level would increase. You don't see that.

Super high oil temps. You don't see that either.

I'm so paranoid with my 2019 that I change the oil / filter every 3000-3500 miles. Usually closer to 3300. I rarely use the recommended 0w20 and use 5w20, 5w30 or I've even used 10w30 w/ no issues of any kind.

 

[Cdavid575]

It’s a 2017 with 159k on it. Oil change every 4-5k since I’ve owned. It was an enterprise car we bought in 2019 and I noticed some gunk in the oil cap. After a year or so it started blasting white smoke out the exhaust after you would coast and get back on the throttle. I found that oil was collecting in the baffles of the valve cover then my intake would suck the oil through the pcv valve and through the engine. Idk if bad venting was cause of the sludge or if it was poor maintenance at enterprise but after seeing others with similar issues I’m assuming it’s more than poor maintenance. I agree it doesn’t really make sense but a buildup of gases will cause sludge so that’s where my mind goes. Looking forward to getting a better look inside the engine when I get this thing out.

 

[PoManzPathy]

It’s a 2017 with 159k on it. Oil change every 4-5k since I’ve owned. It was an enterprise car we bought in 2019...

Our 2019 was also an ex-rental. I bought it in Oct 2019 with ~25K miles on it (for $24K. Those were the days..). The car fax showed one oil change at around 12K miles, then the dealer I bought it from did an oil change just before I bought it. It likely only had 2 oil changes in that 25K miles that it accumulated in ~10 months of rental service.

Do you recall at what mileage your 2017 started billowing smoke? Knock on wood, ours still remains smoke free w/ 91K on it. Our 2019 would likely be rotted to pieces by ~160K even though I try to keep up with fluid filming it. I just did an oil change on it today and I have rust spots so bad on the engine oil pan, it will be rusted through in a year if I don't do something about it. The joints on that front exhaust flex joint are about gone as well. The rust-belt blues.

 

[Cdavid575]

To be honest, at the time I couldn’t find anything beyond OEM and that’s exactly what I replaced as well. Cam chains were fine. Also front gasket seals and the variable cam actuator seals.

I see a kit on z1 off-road, it comes with all gears, tensioners and chains for about 1200$. Does this sound about right? I havnt seen any other kits for sale and was shocked by the price so I want to be sure I’m not missing something. Obviously I’ll need all gaskets and o rings as well.

 

[PoManzPathy]

I see a kit on z1 off-road, it comes with all gears, tensioners and chains for about 1200$. Does this sound about right? I havnt seen any other kits for sale and was shocked by the price so I want to be sure I’m not missing something. Obviously I’ll need all gaskets and o rings as well.

How does that $1200 compare to one from a Nissan parts counter price? I'd think Z1 off-road's kit is OEM.

 

[JBOOKMAN12]

It’s a 2017 with 159k on it. Oil change every 4-5k since I’ve owned. It was an enterprise car we bought in 2019 and I noticed some gunk in the oil cap. After a year or so it started blasting white smoke out the exhaust after you would coast and get back on the throttle. I found that oil was collecting in the baffles of the valve cover then my intake would suck the oil through the pcv valve and through the engine. Idk if bad venting was cause of the sludge or if it was poor maintenance at enterprise but after seeing others with similar issues I’m assuming it’s more than poor maintenance. I agree it doesn’t really make sense but a buildup of gases will cause sludge so that’s where my mind goes. Looking forward to getting a better look inside the engine when I get this thing out.

Wow same thing here enterprise car same scenario a year in boom smoke. amazing I was going crazy

 

[JBOOKMAN12]

I hope to do this soon, since I am having the same issues everyone else is having with their 2017. I am skilled enough, and competent enough, to do the repairs on my own. By that, I mean I can take things apart and put them back together with no problems. However, timing chains freak me out. Without access to any repair manuals, how do I ensure that the timing is still correct when I take the old chain off and put the new one on? As long as nothing rotates should I be good? From your write up it sounds like I can take it apart and put it back together without having to do anything but turn the car on when I'm done, is that correct?

Hey that’s crazy my car is a 2018 it’s been sitting now for 6 months I spent around 2,000$ still don’t know what is going on just smoke and noise last guy said it needs engine another one said it’s the chain I’m confused

 

[Cdavid575]

Wow same thing here enterprise car same scenario a year in boom smoke. amazing I was going crazy

It’s not a fix but pulling the pcv line off and plugging the vacuum line that goes back into your intake should stop it until you can take it apart

 

[Labranson]

I am currently going through this exact same issue. First started having white smoke and changed the pcv valve and the white smoke stopped but now dealing with a no crank no start and a P0390 code. I just bought the Z1 off road timing kit. I will update when complete.

 

[Cdavid575]

I am currently going through this exact same issue. First started having white smoke and changed the pcv valve and the white smoke stopped but now dealing with a no crank no start and a P0390 code. I just bought the Z1 off road timing kit. I will update when complete.

Good luck man! I have my engine out now, pulling the cover off. I also bought the z1 kit, it seems to come with everything including water pump.