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NEED HELP: Smoky Murano - Oil Traces Through the Intake Manifold and Throttle Body!

9K views 7 replies 5 participants last post by  jaypro3 
#1 ·
Hi guys

Really need some help...

Bought a Murano (3.5 AWD) about a month ago.

Noticed it was smoky at start up and also if you hold the accelerator down. WHITE smoke (defo not blue).

It was due a service, so decided to do a full service and also replace the spark plugs and the PVC valve on the rear cover. Also replaced the intake manifold gasket (the main lower one with six holes in a row) and rocker cover gaskets. Do the job properly, basically. All DIY.

My hope was new spark plugs and PVC valve would sort it.

No change. Well, it's a bit perkier, but still smokes.

Now, the interesting bit... The spark plugs were pretty shot - black burning on the tips. Additionally, all up the inside of the intake manifold and even the throttle body had traces of what I assume is burnt oil (amber coloured staining). I assume that's not normal!

The car appears to be using oil also as the level had dropped a fair bit in only 50ish miles since the service.

So, my first question is: any idea of the possible/likely cause?

Thanks guys!!!
 
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#2 ·
Well white smoke means that you are probably burning up some coolant, which from what I know could be a bad headgasket. The issue with the burnt oil looks like it might be a separate problem from the white smoke, but a bad/clogged PCV valve, prior to the change, could have caused some of the issue as well...(actual loss of oil could be from a number of things...high mileage/weak piston rings, oil leak, etc). I would look to get some help on here from those that know a little bit more about these specific issues, or if they've dealt with the issues previously themselves. I'm just kind of brainstorming without know much more specifics about your vehicle exactly.
 
#3 ·
Thank you

Many thanks for the feedback.

Yes, I initially thought that the smoke could be caused by a bad PCV valve (Positive Crackcase Valve - the plastic one on the rear rocker cover). Especially, as I now know from having stripped it down, on the last spark plug change they were VERY lazy and only replaced the fronts, leaving the rears in much worse condition - meaning the PCV valve has not been changed for a good while either :eek:

But I replaced the PCV valve and it's not made any difference. That said, I've only done a short test run of a couple of miles. Maybe it will burn off before running clear???

Then I thought maybe the head gasket - as you suggested. However, there appears to be no coolant issue. I'm not getting any milky oil nor loss of coolant. Just a smoky exhaust.

So I'm wondering maybe the breather lines, and also breather valve (if there is one?) How do I check those??

I'm hoping it's an emmission based issue as head gasket is engine out and major. But it doesn't seem quite right for the head gasket. No loss of performance either.

I read a forum post from a chap who's problem sounded very similar, and he got Nissan to fix it by changing the front and rear emissions valves. The rear I imagine is the PCV valve - no idea what the front could be? Emissions Pressure Valve to the left on the Intake Manifold (circular with 90 degree arm pointing downard)??

Any ideas?
 
#4 ·
The emission control system is designed to turn vehicle emission into less hazardous stuff, including water vapor. The white smoke you see is probably just that. If you still see white "smoke" after a prolonged drive in a warm day, then you might have a problem. Otherwise I would not worry about it.
 
#5 ·
Thanks guys!

I've been having a chat with my step Dad about this. He used to do work on his own cars back in the day and is suprisingly knowledgable.

He asked if I had noticed it kick out a load of smoke after coming down hill for a bit. By chance, I noticed this exact thing happen about a mile from his house on route!

He explained it's not about the braking, but basically stopping accellerating for a while - which builds up a little oil, and then popping the accellerator back on, and poof - lots of smoke in one big blast...

He thinks this is most likely the valve seals. He says that the oil can seep down through the worn seals and into the chambers, where it then does not ignite as it should (of course) and gets thrown out of the exhaust. The downhill also puts the oil more towards the front of the engine and over the valve seals, so amplifies the issue.

So I'm thinking maybe the smoke is not white? Does not look 'blue' to me, but is also not white like a cloud - if that makes sense!

Doing a little more research online - his theory could well be correct.

My major issue is this: can the valve seals be replaced without removing the head???

It seems they can on many models of Nissan, but worried that the cam chains may stop this being possible? If the head has to be removed then I believe the engine has to come out and it's major!

Any ideas or thoughts on this?
 
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