Hello everyone - I have two VQ35DEs in my garage right now - an early 2003 G35 sedan and a 2003 Murano. I'm posting here because you guys like mods, push your cars to the limits, and know how the engines work. The Murano forums and G35 forums just weren't cutting it and I need some help. I also have an old chevy and price myself on doing all of my own work. I've built engines and transmissions on the old chevy so I understand the basic mechanical concepts of an engine. This last trip to the dealership was my first in about 200k in miles across my last three cars and I want it to by my last in as many miles.


Hope you don't mind me asking for help on a Murano here!

The Murano (94k soft miles) has some pretty severe detonation / pinging / spark knock under heavy throttle starting around 2500 RPM all the way up through the range to the redline. It sounds like "marbles shaking in a can" and the car is way down on power when it happens. I've also run a can of seafoam through the brake booster vacuum line. Under light/medium load the car has no issues.

THe issue is load related because i cannot get it to ping while free revving and if I put the car in a lower gear the pinging occurs at a higher RPM but only under heavy load. It does it while the car is hot and cold.

The car runs on 93 octane fuel.

I've replace the knock sensor, plugs, cleaned the MAF sensor, dealer inspected catalytic converter and precats, dealer checked valves, and the dealer did a full diagnostic with the Consult II. I checked with my own OBDII scanner and there are no codes. The dealer did agree that it is spark knock.

Here's the strange thing... once in awhile I cannot get it to ping.

Since this happens intermittently I am leaning towards a sensor or something electromechanical. THe dealer gave up and recommended the suite of money wasting treatments (fuel injector cleaning, decarbonizing, etc...). I'm done with the dealer because I think they are lost when there are no codes to tell them what to do and take a parts changer vs. mechanic approach to things.

The knock sensor is supposed to retard timing when detonation is detected and my ECU is obviously not able to do so --- so I'm thinking that CVTC (continuously variable timing control) may be the culprit here. For those of you who don't know about CVTC, it advances/retards the intake camshaft to optimize cam timing for RPM.


Some questions:

- Does anyone know what paramaters are used to control timing? (perhaps I have a sensor that reads wrong but is not dead (therefore no DTC))
- Does anyone know how the VQ35DE variable valive timing works (perhaps one or both cams is not being advanced/retarded properly). Does a servo rotate the relative position of the camshaft? - what are the parameters used to actuate the valve timing?


I really want to get this fixed for two reasons:
1) My wife and kids use this car every day and I want it to be dead reliable
2) Don't want the detonation to blow a hole in a piston, break a spark plug, etc and blow up my engine.

If I can't git this fixed within a reasonable period of time I'm going to have to sell it!

Thanks in advance guys!

Brian

 

Have you tried a compression test for all 6 cylinders? Have you tried a leak down test as well which should also tell you if it's a valve train problem? It could also be a bad head gasket(s)

 

I like the compression test and gasket concept - if only to continue
The process of elimination. Without throwing a code i'm wondering
How else you could identify a source.

Interested in hearing more on the timing too.
Good luck. Is there a recordable sound?

 

Crazy issue your having. I'm still leaning to clogged cats. Do you have an infared thermometer? If you power brake it does it happen? I forget but I think if the cats get over 4-500 degrees there's a problem. Also I wonder what the fuel pump is doing while this happens.

 

He can take the cats off and drive the car for a bit to see if something happens. It wont be an issue. It could be that one of the pistons is gone. It happens. Compression test and leak down test need to be done.

Buy a used engine. It's only like $600 for the regular one. Get a hoist and change it yourself.


EDIT The Murano only has one cat or 2? I forget.

 

Hey guys - thanks for the replys. Forgot to set the preferences to notify me of replies.


I've put about 1000 miles on the car since the original post and the problem persists. The conditions to create the symptoms are clearer to me now.

Under light acceleration the car is responsive/normal - can get to 60 MPH as expected. Under modertate acceleration, the engine pings and it has greatly reduced power.

As a test I floored it at 40 MPH going up hill - the CVT dropped down and the engine revved to 5500 RPM. It took 10 seconds to accelerate to 50 MPH. It pinged the whole time.

Under light acceleration, and the same conditions I can accelerate from 40 to 50 MPH in the same time but at about 2200 RPM. Set the cruise control at 75 and when the car enounters a hill requiring a decent load to maintain speed, the engine pings. Otherwise, it cruises at 75 MPH all day with no issues.

That being said, we went through a whole tank of 93 octane fuel at 75 MPH from Chicago to northern Wisconsin and got about 17 MPG which kind of sucks. The best we've been able to get in recent history is 19 MPG at about 60 MPH.




Andrei - The Murano has three catalytic converters - two are "precats" and they are located just after the exhaust manifolds. The other is the main cat and is located where the bank exhausts merges into a single exhaust on the Murano.


Andrei and lgear080 - So I asked the freaking dealer to troubleshoot BEFORE changing the plugs and of course they did not so I'll have to remove the intake plenum (5 hours and $50 gasket - the joys of sideways mounted engine) to check the back three cylinders but a compression test on the front three will be next on my list. I inspected the front three plugs and all were normal and I suspect (hope) that if the 3 plugs ont the backside of the engine were bad the dealer would have tried to sell me something. A bad piston would be crappy but I'm not going there yet due to good looking plugs.


I'll make an audio file but the knocking sound is captured well at about 25 seconds in this youtube video-
http://www.youtube.com/watch?v=GGJZ6...eature=related
When detonation occurs, the pulsing is erratic like the video but the existence of detonation is constant until I let off the gas.

0jiggy0 - I'm still hoping that the issue is as simple as plugged cats and Look to see if I can remove them without completely ruining the exhaust. Great idea on checking the temp - now I have an excuse to get an IR thermometer. Pinging does not happen when engine braking. Why do you ask about fuel pump - do you think it could be a lean condition? Wouldn't the O2 sensor pick that up and throw a code?

Back to the original Q for a sec - anyone know how the variable intake valve timing works? I am thinking there is a servo which roates each intake cam on the chain pulley to retard/advance valve timing. Don't know how much of this is monitored by the ECU.


Many thanks!
brian

 

Did some HW last night (read portions of the service manual) and the VQ35DE varibale intake valve angle (timing) is hydraulically controlled. Each head has a solenoid that pulses according and operates a valve that adds or removes oil pressure to vanes connected to the intake camshaft.

The solenoid pulses change to advance or retard the opening of the intake valve relative to the exhause valve to trade horsepower for torque or vice versa.


Here's the thing - I changed my oil cooler gasket right before this issue started happening so I'm thinking maybe some debris is stuck in one of the passages or the solenoid valve. THe primary driver of the car (my wife) noticed the noise soon after the oil change - may have been there immediately but with the radio on and two active kids she may not have heard it.


BUT - like everything else on the car, the ECU expects intake camshaft position angle and measures it with the camshaft position sensor. If the expected camshaft retard/advance is not achived, the ECU is supposed to throw a code.

In your experience, are there situations in which a problem is encountered and a code is not generated? In other words, are there any weaknesses in the system? Is the system fool proof?

Thanks,
brian

 

Update:
Haven't measured the exhaust temp or compression yet but I have found something peculiar and have confirmed that the issue is spark knock.



I tried driving with the MAF disconnected and this generated a MAF and IAT code. When the MAF was plugged back in, the car resumed pinging and had no power. Next I grabbed my OBD II and cleared the codes and the pinging went away. Without the pinging, the power gain is significant. After sitting overnight, the pinging was back.

MAF was replaced with no improvement.

Over the last few days I have drivin this car to work and have been able to make the condition go away each time by clearing codes (even though no codes exist). Sometimes, the issue goes away immediately after using OBDII to clear codes and sometimes it takes a few minutes.

The car has seen 2000 miles since this issue started occuring and the only time the pinging has gone away was when OBDII was connected and codes were cleared.

I've learned that some learned parameters (like long term fuel trim) are discarded when codes are cleared. So - I'm getting closer to solving the issue but am more confused than ever.

Question: what kind of problems could be causing pinging that can be cured by clearing codes in the ECU. And - if the engine runs very well after clearing the codes, why does it revert once it's cooled down?



Thanks,
Brian


p.s. Spark Knock confirmation - when the noise occurs the timing shoots to zero. This means the ECU and knock sensor are working but the condition causing the pinging is not solved by retarding the timing.

 

Well today I got a call from my mother saying her 2006 Murano was not running well. Long story short it has a random misfire. First problem in 78k miles. The valve covers do have leaking spark plug tube seals but there is no oil in the tubes, only on the coil packs and very little and only some areas of the coil packs. Not drenched in oil at all. Have not checked the rear ones yet but I will tomorrow when I have time to take off the intake system.

As far as variable valve timing being a problem, it is not. It's hydraulic. BMW N55 uses electric variable valve timing and they need to worry about it, not us.

Unless you run a compression test you wont know for sure what the problems is but here are some things that can cause misfires.

MAF sensor which you say you changed.
Vacuum leak after the MAF sensor.
Low compression cylinder or cylinders. One piston could be gone completely.
One of the head gaskets went bad.
Air Fuel ratio sensor can cause it.
Catalytic converter can cause it as well.
Low fuel pressure.
PCV hose is leaking or is not connected.
The ignition wiring harness is damaged.
The injector wiring harness is damaged.
Bad injector which I highly doubt as ID makes quality injectors and out of 7 Nissan cars in the family I have never had a fuel pump or fuel injector problem.

 

UPDATE
Turned out 3 spark plugs were out. The dealer fixed it. I didn't have time and it's way too cold.

 

the pinging your hearing..does it sound like its coming from the bottom end of the motor? with these vq motors they need to be topped off with oil especially the older engines out there as most know. i doubt your cats are clogged as that usually quickly will throw a cat code however the cat nearest to the firewall is the most common cat that fails on the muranos.

 

Found this on another forum:


- Use NGK LFR6AIX-11 Iridium IX Spark Plug. It's one step colder than the standard LFR5AIX. With NGK, the higher the number, the colder the plug. Do not use anything colder than that, because that would lead to spark plug fouling.
- Change the base timing by setting it back 2 degrees. The Nissan Consult tool allows for adjusting the base timing +- 5 degrees. This will not harm the engine. My mechanic had the necessary programming tool to adjust this setting in the ECU. Unfortunately simple OBDII tools will not do this, you'll need to take your Murano to a stealership (that will charge you about $100 for pushing two buttons on the Consult II) or find a neighborhood mechanic with the compatible scanner.
- Last but probably not least, even despite several Seafoam treatments, my mechanic found extensive carbon build up in the intakes. So he did an extensive cleaning. I also dia another Seafoam just before oil change, but this time let the Seafoam stand in the engine overnight. I think these two actions hopefully got rid of all the gunk that was in the engine.


I'm not expert, but try this list:
1) Also, are all the vacuum hoses hooked up?
2) Is there any way you can test the ignition coils?
3) Can you recheck the new plugs you put in?
4) Do you have any oil in your spark plug holes (leaking valve cover gaskets)?
5) Can you check the injectors to make sure they are working correctly?

That list probably won't diagnose your problem, but I wish you luck.

 

Ignition coil can be tested. FSM has details. Use a metric ruler. Anyway, my mother called me this morning while I was getting my beauty sleep saying the Murano was acting up again. She said the car had a constant surging idle (not in those words) and she was going back to the guy who fixed it who WAS NOT the dealer. I told her to bring it to me first so I can look at it.

Turns out the half *** "mechanic" left the entire hose after the MAF sensor disconnected causing a massive vacuum leak, I don't even know how the car did not stall, she drove from Lawrenceville to Alpharetta and back like that. Gawd knows how much he planned on charging her for it even though it was his fault he left the intake open.

 

Update:

Brought it to a local (non dealer) old school mechanic and while they were test driving the dash cut out twice and a code finally showed up. Up until this point no codes had been detected.

CVT C/U FUNCT [P1700] and CAN COMM Circuit [U1000]

They were not able to proceed because they don't have the nissan specific software. The mechanic thinks that the TCM (TCM does a lot of work due to CVT) and the ECM are not talking and my CVT is in some kind of default mode. In this default mode it is applying to high of a ratio (low numerical ratio) and essentially causing the engine to lug causing spark knock.

This explains why my problem goes away at times.

There is a Nissan TSB that lists the codes above leading to random transmission problems that often appear to the driver as hesitation or surging. In bad cases, the car will not accelerate. The TSB indicates that bad grounds often cause CAN (Nissan acronym for the bus that links together all of the computers) failure. Last night I cleaned up my main battery/body grounds and tonight I will dig into the ECM grounds buried deep behind the dash on either side. The TSB specifically mentions these grounds.

The fact that my problem is intermittent (there about 95% of the time) and that the dash cut out a few times leads me to believe the issue is electrical. I would be extremely pleased if it is as simple as a bad ground.


Here's a link to the TSB
http://www.google.com/url?sa=t&sourc...GxhVVywvETCg8A

Brian

 

Update?

 

I pulled apart the driver's side dash, located the ground terminal, cleaned and reattached.


On test drive, the knocking and low power remained. I pulled over, connected my scanner and cleared the codes. Knocking gone + power was back.

On the next day I test drove the car and the knocking/low power was present on two WOT runs. On the third and subsequent WOT runs, the problem was gone.

Tonight I will pull apart the passenger side dashboard and get at the second ECM ground. Whatever it is that is causing my problems, it appears to be electrical and related to the CVT. Note that many Murano owners look at early CVTs (especially 2003) as huge repair bills waiting to happen. Luckily, Nissan extended the CVT warranty to 10/120,000!

Brian

 

ive seen codes on a bunch of nissans that always tell you to check you ecm grounds located behind the dash. every time ive checked them the grounds were fine. but its good to check for peace of mind. what you may want to consider doing is locating another ecm as that could be your problem..ecm could have a fault burned in it causing errors along the can line to your tcm. have you ever pulled any U1000 U1001 can codes?

 

Well- I spent hours locating and cleaning up all ground connections related to computers and the problem persists. All ground were sound to begin with.


The P1700 code was accompanied by U1000 abd U1001 - when you say "pull" is there a way to pinpoint where the CAN communication failure occured? Unfortunately, I cleared the codes and they have not yet come back.

My last ditch effort will be to have the dealer run through the full suite of CVT tests. If that doesn't produce any real leads the car will be gone? Anyone wanna buy a Murano?

Thanks!
Brian

 

yea i figured the gounds would be fine. how many times have you seen the p1700 and "U" codes? unfortuantly there isnt really a way to accurately pinpoint a problem with a CAN system at home and without a nissan scan tool.. the CAN system is run off 2 twisted wires pink and blue in color that as you know run everywhere in the vehicle to tie everything together. without a scan tool i dont see CAN diagnosis ever happening. CAN codes are often caused by bad grounds which you checked and sometimes even your positive battery cable being slightly loose.

 

Follow up....

p1700 and U1000 abd U1001 codes never came back but the pinging is still there and getting worse. These days the engine will ping almost constantly at 75 MPH.

I brought the car to a different Nissan dealer and they told me that what I am hearing is normal for an "old" car. Apparently 97k miles is OLD for Nissans and my expectations for a smooth running engine on a car that has been well maintained are too high. Even showed them that the timing is going to 0 degrees when pinging occurs and they said that it is normal. To add insult to injust, the dealer charged me $100+ to tell me the pinging is normal.

In a last ditch effort I replaced the battery (it was on its last legs anyway) thinking that it may be causing grounding / voltage issues but that didn't help.

So - I will be trading in this car and unfortunately someone else will have to deal with it. I have tried and so have two dealerships and an independent mechanic. Funny that Nissan says everything is cool and the independent says there is a problem somewhere. Anyone who knows anything about engines knows that pinging is very bad and will eventually drastically shorten the life of an engine.

Brian