2008 having with a problem that can't be found.

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padgett
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2008 having with a problem that can't be found.

Postby padgett » Wed Jan 15, 2020 11:23 am

Hello, all.

I love my pathfinder and have had a lot of great road trips so I am hoping I can get a fix for my issues that does not cost more than what I paid in the first place.

It started with a sort of "knock" from the engine and some vibration at a stops. I had not changed the spark plugs so that was my first go. After that the issue was sill there but I was getting the Random cylinder misfire code. I took to to one shop and they fixed and oil leak, and intake hose, and my 02 sensors, but the problem was still there. They suggested looking into the timing chain. That was going to be pretty pricey, so I went to a place for a second opinion, he has check about everything in the engine you can, also changed the fuel injectors one side, because he saw some white corrosion. That did not fix it. He made some called, did some research and came a cross the catalytic converter idea. He looked in to mine and found a 30% blockage and some melted parts.

Does this track with anyone else's issues?


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eieio
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Postby eieio » Wed Jan 15, 2020 12:03 pm

Some catalytic converter problems can result in engine damage (piston/ring/cylinder walls) from loose converter material getting sucked back into the engine.
A compression test might be of benefit.

padgett
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Postby padgett » Wed Jan 15, 2020 12:11 pm

Compression test and a leakdown test have all been done. From what I understand this shop has done about every test they can have ruled out the issues being the engine.

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ShipFixer
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Postby ShipFixer » Wed Jan 15, 2020 1:09 pm

Cats have my vote...

padgett
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Postby padgett » Wed Jan 15, 2020 1:14 pm

Just got off the phone with the mechanic. He said he changed the them and drove the car around for about 10 mile. No codes popped up. It has a slight vibration at idol, but nothing he feels I should be worried about. Over all I feel I came out pretty good. Because he changed the fuel injectors that didn't need changed, he asked if he would leave those in and he would eat the cost of the converter replacement. So $2100 is way cheaper than the over $6000 the other place was going to charge me, by saying it was my timing chain, that apparently would not have fixed it issue.

jlocal
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Re: 2008 having with a problem that can't be found.

Postby jlocal » Sun Jun 28, 2020 10:12 am

I know this post is several months old, but I went through the same problem. Got my PF back 3 weeks ago and still have very rough idle at stops. Not as much since back from the shop, much improved, and 95% of the time smooth idle. I had every sensor changed, new plugs, new injectors, PCV valve, new timing chain and tensioners, and new cayts. Passed smog but 5% of the time still gets a bad shake at stop. The explanation I got from a Nissan tech is that the intake is to small for this size engine, 4.0, so I guess I'm hoping for the best.

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smj999smj
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Re: 2008 having with a problem that can't be found.

Postby smj999smj » Sun Jun 28, 2020 7:00 pm

I wonder how he came up with the notion that the intake is too small as it's the first time I've heard that. VQ engines, in generally, have always had a slightly rough idle going all the way back to the 95 Maximas.

jlocal
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Re: 2008 having with a problem that can't be found.

Postby jlocal » Mon Jun 29, 2020 10:44 pm

That is good to hear, I guess, he told me that is the reason for the rough idle. He said it was an engine flaw when the engine was developed. The PCV valve does not do the job and oil gets collected in the intake manifold. My PF is running much better after all that has been done. But still shakes 1 out of 10 stops. So if that's the norm I'll be happy with that. I know from reading in the forum there is a rough idle with these engines. So, like I said, I'm happy with the way it's running now.

jlocal
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Re: 2008 having with a problem that can't be found.

Postby jlocal » Mon Jun 29, 2020 10:57 pm

I'm not sure, he works on Nissan exclusively and said the intake is to small for this engine. The PCV valve is not sufficient for the engine size. Oil gets into the intake manifold and causes problems. My PF is running good now with all that was done, but if a rough idle is a normal thing, I'm ok with that. It just seems strange with no strain on an engine it would have a shake or stutter in such a way it does.

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palmerwmd
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Re: 2008 having with a problem that can't be found.

Postby palmerwmd » Tue Jun 30, 2020 12:35 am

jlocal wrote:
Mon Jun 29, 2020 10:57 pm
I'm not sure, he works on Nissan exclusively and said the intake is to small for this engine. The PCV valve is not sufficient for the engine size. Oil gets into the intake manifold and causes problems. My PF is running good now with all that was done, but if a rough idle is a normal thing, I'm ok with that. It just seems strange with no strain on an engine it would have a shake or stutter in such a way it does.
I once had a brand new 350Z .. it has a 3.5L VQ engine very closely related to this one..

Also had a bit of what seemed to me like a lean misfire at idle. or a stumble, or a roughness.. whatever u wish to call it..This was brand new.
Talked to dealer about it at lenght.
They insisted it was a non problem.

My current 4.0 liter engine does it as well.
But again dont know how "rough" is rough on yours.

(Quite common with the big V6s from Nissan perhaps because of how aggressively they are tuned for power?)

jlocal
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Re: 2008 having with a problem that can't be found.

Postby jlocal » Tue Jun 30, 2020 9:20 am

Before I had all the maintenance done the idle was rough quite frequently. Now, it idle's smooth but every now and then when stopped, RPM's drop and seems like it wants to stall, but never does. Like I said, if that's normal for these 4.0 engines, I'm fine with it. I also believe the PO did not take good care of this PF, as it only had 92,000 miles.

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palmerwmd
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Re: 2008 having with a problem that can't be found.

Postby palmerwmd » Tue Jun 30, 2020 10:39 am

jlocal wrote:
Tue Jun 30, 2020 9:20 am
Now, it idle's smooth but every now and then when stopped, RPM's drop and seems like it wants to stall, but never does. L
I owned 7 vehicles with a VQ series engine. 4 of them did that.

jlocal
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Re: 2008 having with a problem that can't be found.

Postby jlocal » Tue Jun 30, 2020 11:50 am

That is good to know, I'll rest a little easier now!

silverarrow27
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Re: 2008 having with a problem that can't be found.

Postby silverarrow27 » Tue Jun 30, 2020 1:27 pm

Is it the air intake or the intake manifold is too small? If it's the air intake, if the VQ is running off a MAP sensor instead of a MAF...take it for a test drive without the air intake installed if you want to test your mechanic's theory. Usually the air intake is about the same size of the throttle body though so I'm leaning towards intake manifold?

jlocal
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Re: 2008 having with a problem that can't be found.

Postby jlocal » Tue Jun 30, 2020 7:10 pm

Well this being my first Nissan (I really do like it) I'm hearing on this forum that all these 4.0 engines have a rough idle. Since I got it back it really run great except for the once in a while shake at a stop. Since it's running so good now, I don't want to do any more testing. I'm still learning about this PF. It does seem to be quite heavy duty.


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