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96 VG33 intake manifold oil deposits


tpounds
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Hey folks,

I've been lurking a bit but I'm finally getting to work on my pathy(ies) after a cold winter and have run into some problems and I could use some advice & knowledge. I bought a 96 LE (green) manual trans 4x4 in 2016 that had transmission problems and then stumbled upon another (black) one just like it last year on craigslist that did not run with supposed fuel delivery problems. The previous owners of the black one said that they thought it was a problem with the fuel injector pressure regulator. They told me they had already replaced the fuel pump & fuel filter and had a mechanic tell them it was probably the regulator because they weren't getting enough fuel. I'm just a shade tree type mechanic but don't mind getting a little dirty in the right conditions so terminology can be a bit rough here so please bear with me. :)

 

I started removing parts and inspected things to possibly find what needs to be replaced. I've dismantled quite a bit of the topside of the engine and found some head scratcher issues along the way. When i got to the throttle body i noticed a little black oil in it and when I took off the intake plenum black oil was clearly visible inside it and the lower manifold. When I removed the tube that runs from one valve cover to the other under the distributor there was the tip of a pipe scraper about 2" long broken off inside. Ok, whoever left it in there is in need of a Jethro Gibbs head smack but thats beside the point. Without taking the fuel issue into account this leads to my first questions: 

 

Is that enough to cause the disrupted flow of air and oil to make it head towards the throttle body or manifold in some way? 

If not, should I be looking for something else that is causing this like the PCV or something? 

 

Surely the scraper is not good but I'm looking for help / advice / thoughts on the oil in the intake manifold & plenum as this may be getting into a little more than I'm used to/comfortable with. I do have a plan I concocted and have parts waiting to be installed once I'm ready but do i need to go a little further like remove the lower manifold and replace those gaskets?

 

I currently have the following parts ready for this mighty project:

Spark plugs 

Spark plug wires 

Distributor cap and rotor 

Throttle body gasket

Thermostat (I might as well) 

EGR to manifold gasket

Plenum gasket

PCV valve 

Valve cover gaskets w/grommets

Fuel filter (just in case) 

& the fuel pressure regulator 

 

Other than the stated issues above, cleaning everything and oiling moving parts I think I'm good to go parts wise, but it also leads to thoughts of further dismantling. The oil in the manifold worries me more than the fuel delivery, I hope that will be fixed with what I've already invested in. This is also further than I've been on any car I've owned previously so I'm trying to not get overwhelmed. I can say that my green pathy is still intact so i have it for reference when putting everything back together.

 

My brain is saying "Is it starting to look like there is a problem with valves or heads?" I know a cylinder pressure test might tell me more but I haven't got that far yet. Should I just go rent the pressure tool to do that or am i chasing fictitious problems? "What would you do?" 

 

I apologize for being so long winded but I'm trying to remember everything I've planned all winter & I'm a little nervous. While I have it this much taken apart, what else? I have all the time to do things right but am limited to a budget. With all of this said, I'll add a couple of pics... 

 

Thanks! 

 

https://drive.google.com/file/d/1IrVwTb475Qgws_gleWh-xmF324cjO0V-/view?usp=drivesdk

 

https://drive.google.com/file/d/16jvy4ggRdUDO8mwccD0wiQWbHDnZGR-w/view?usp=drivesdk

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Oil in the throttle body and intake is pretty common due to the pcv system. It doesn’t necessarily indicate a problem. However....a failed pcv valve can cause all kinds of problems. Clean the throttle body and intake plenums thoroughly with throttle body cleaner and replace the pcv valve. Check for vacuum line cracks and leaks as well 

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First pic looks normal. Second one wants me to request permission to see it.

My intake was black like that too. Twenty-odd years of exhaust gas recirculation and positive crankcase ventilation introducing soot and oil vapor into the intake will do that. I cleaned my throttle body (actually got a little power back doing that on my '95) and knocked out the carbon chunks that build up in the EGR port because I didn't like the idea of crunchy bits going into the engine, but I don't think the rest of it's really hurting anything or indicative of a problem.

 

Pipe scraper, like the end of a bottle brush? They're actually supposed to have one of those in the PCV system, it's just something for the oil vapor to condense on so it runs back into the engine rather than getting sucked into the intake and burned. This guy reckons it's to keep oil from fouling out the MAF sensor. Speaking of which...


If you're chasing a lean condition, take a look at the MAF sensor, too. That's the sensor between the intake tube and the air filter box. It's got little filaments inside that are electrically heated and cooled by the air going into the engine. The computer monitors the filaments (their resistance varies with their temperature) to see how much air it's adding fuel to. If those get insulated with gunk, the computer sees less air coming in than there is and the mixture goes lean. Ended up being the problem on a friend's Buick once. White spark plugs, went into limp mode if you pushed it hard, obviously running lean. Cleaning the years of schmutz off the MAF was all it needed. You can get special MAF cleaner, though I've used carb cleaner and isopropyl (think it was isopropyl) alcohol without issue. Be very careful not to break the filaments, and don't use a cleaner that leaves a residue.

 

Also, do you know when the timing belt was done last? Probably not what you want to think about when you're up to your elbows in one thing, but these are interference. I got mine without service records, so I just went ahead and did the belt before I put it on the road to be on the safe side.

Good luck!

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Thank you both! I'm worrying a lot less now. Yeah I need to host photos at a little more forum friendly host but I fixed the sharing for now... 

 

Getting to the iacv gasket first, it's not on RockAuto so I'll look elsewhere. I did buy 10 feet of vacuum hose as well so a lot of that is going to be replaced just to be sure. Looking at the pieces closest to heat generation prioritized. Thanks again!

 

That's just weird on the bottle scraper but ill clean it and put it back in. I know there's a lot of info here on cleaning certain sensors & parts so I'll start looking at that too. As far as going that extra mile to get things right, that's what i want to do. I'll look at the manual to see how involved the timing belt replacement is. I'm not certain about any service done other than what I stated previously so I appreciate the insight. 

 

I guess I'm just a worry wart so thank you both very much, I feel less overwhelmed already. Cheers! 

 

Edit: One little thing, I'm already cleaning the plenum but should I leave the lower manifold alone so as not to get any of that gunk to drop in? I'm hoping to leave the lower manifold alone and pray that it will clear itself over time. 

Edited by tpounds
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22 minutes ago, adamzan said:

I was able to use Rtv gasket maker on my iacv gasket just fine. Couldn’t find a gasket anywhere.

 

That's what I was thinking. $3 part with $10 shipping just isn't right. 

Edited by tpounds
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It's not a VQ35 it doesn't have that problem lol

 

FYI Ishino Stone is the OEM gasket maker for Nissan. At least for the older ones.

Edited by adamzan
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1 minute ago, adamzan said:

It's not a VQ35 it doesn't have that problem lol

 

FYI Ishino Stone is the OEM gasket maker for Nissan. At least for the older ones.

Ah you’re right. Didn’t notice it was a vg 

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