Any Direct Injected 300gt / 250gt V35's?

[chad bob]

You all seem to be on the right track.

The best plan of action is to remove the cover and lower portion of the intake manifold and give them both a damn good cleaning, you can use water and degreaser on the intake parts once you've removed them but clean the throttle body with brake and parts cleaner / caby cleaner only, you don't want water in the electronic throttle.

Removing the plenum / manifold is pretty straight forward and re-fitting is just as easy, all the fasteners are accessible without removing much else.

Edited June 20, 2010 by chad bob

[o2bfit]

One other thing. It is recommended not to disconnect the wiring harness and hoses from the throttle body when cleaning it.

I also found the idle after I cleaned the throttle body was high around 1100 rpm. I had to reset the ecu and perform the idle relearning procedure to get it back to normal. There's a post in this forum explaining how to do it.

[Spong]

One other thing. It is recommended not to disconnect the wiring harness and hoses from the throttle body when cleaning it.

I also found the idle after I cleaned the throttle body was high around 1100 rpm. I had to reset the ecu and perform the idle relearning procedure to get it back to normal. There's a post in this forum explaining how to do it.

Forgive me for my stupidity, but why is it advised to not disconnect the wiring harness and hoses from the throttle body?

Better go off and try and find that post I suppose.

[chad bob]

Forgive me for my stupidity, but why is it advised to not disconnect the wiring harness and hoses from the throttle body?

Better go off and try and find that post I suppose.

You will need to disconnect the throttle to give it a proper clean depending on the buildup present. If you do disconect it, a reset may be necessary so do it anyway as a precaution, an ECU reset is rather easy to do, it involves a series of on / off cycles of the ignition and stomps on the gas pedal to put the computer in diagnostic mode and you can reset it from there. Don't be afraid of the reset procedure, you cannot do any permanent damage to your car in diagnostic mode even if you mess it up completely so go for gold.

[o2bfit]

I found that a few people had an issue when they removed the wiring harness so decided not to risk it. There is plenty of room in the engine bay to clean it. I did the idle relearn procedure to correct my high idle anyway. Its easy enough to do.

From G35driver:

"It's very important to NOT disconnect the harness. If it is disconnected, and the butterfly is moved while cleaning; the ECU will lose the closed or zero position of the sensor. If that happens the car may not start or may run poorly"

There is also a video on youtube - search G35 throttle body. There are a number of posts responding to the video with all sorts of issues:

"Read this before trying to clean your G35 Throttle Body: I preformed everything in this video exactly as was shown, and my throttle body got cleaned but you must understand that it will probably cost you about $180 if you do it all correctly. Disconnecting the TB harness will make your CE light come on and will make the car throttle high. Tried the re-learn over 40 times. never worked. The dealership has to use the Consult II diagnostic tool to correct this. Be warned. Otherwise very helpful"

[chad bob]

Thats odd, I've disconnected removed and manually triggered and cleaned the butterfly multiple times now and never had a problem, just made sure that the butterfly was completely closed prior to re-fitting. I didn't even have to reset the ECU last time and idle is just fine! I wonder what the people that are having issues have done differently? Would be good to find out.

Edited June 22, 2010 by chad bob

[Blade NZ]

I'll ask the guy's at City Nissan when I take it for a service next week.

[chad bob]

Right... As promissed I serviced my M35 today and whipped off the intake plenum cover to see if any buildup has occured since my original cleaning session 20,000Km ago. Under the plenum cover not much had changed, the walls were still rather clean, so blocking the EGR valve has worked so far.

Then I got thinking, perhaps I should dig a little deeper, last time I removed only the plenum cover and cleaned from there, but today I decided to strip it back to the valves to see what it looks like and it ain't pretty!

In hindsight I really should have stripped the entire thing to start with as the buildup gets worse the closer you get to the valves.

This is what I found during removal:

First intake stage removed:

Close up of second intake stage still fitted:

Top of first intake stage with plenum cover only removed (not much buildup, just varnishing):

Closeup of bottom of first intake stage:

Top of cylinder heads, runner buildup (the backs of the valves were caked too):

The removal of the entire intake system took me half of the day, I soaked the bits in degreaser then water blasted them clean, being carful to place them on towels so that the gasket surfaces dont get damaged, I dried the parts and WD40'd the mating surfaces before fitting again. For the runners and back of the vlaves I used a pipe cleaner and pleanty of solvent brake cleaner, I left the runners open for a couple of hours as some of the valves may have been open and I wanted to allow the brake cleaner to evaporate completely before re-assembly. Regarding the gaskets, they are all teflon coated steel, so no need to buy new ones, just clean them carefully and re-use.

Before starting the car after re-assembly, I would let it stand for a couple of hours, it took me quite a while to get it re-started due to residual brake cleaner / moisture in the combustion chamber, but once it started she was singing like a bird.

It didn't feel right making the engine ingest the crap / brake cleaner, but whats the alternative? Wait for a chunk of crap to come loose and block a valve open?

So this is what I'd recommend doing to any NEO-Di NiSSAN motor upon purchasing, if you are not a confident home mechanic then DO NOT ATTEMPT, it is a rather fiddly process. Instead print off the pics above and take your car to the mechanic, if he tries to charge you 2 days labour, tell him he's dreaming!

What have I noticed since doing this cleaning? The motor used to turn over twice before starting sometimes more (2-3 seconds of cranking) now it fires after less than one second! Oh and it goes like a cut cat, used to be able to plant it from standstill and get minimal wheelspin, now it's smoke city in first gear, quite startling the first time it happened!

[Blade NZ]

Hey Chad, nice work there and thanks for the photos. Not a very nice looking situation under all that, actually that is really just plain scary looking and I must say i'm a little disappointed I didn't know about this earlier, probably wouldn't have got a Neo-di as I really don't need the extra maintaince with this. Hopefully once cleaned out and with the use of good fuels and oils it may not reappear as quickly.

I had asked City Nissan to pull apart the plenum and clean it as part of my service,unfortunitely they did not do this. After putting it on their diagnostic computer they found all parameters to be in spec so they deamed it unnecessary.

I was disappointed with this and will now have to find both time and location (and good weather) to look at this myself.

Still with your good work & photos the task doesn't appear as hard, just time consuming which is the biggest hurdle I have at the moment. I need the car everyday to ferry the kids to school & back and I work in the weekends. Oh well, one day!

[chad bob]

Indeed it is time consuming and some of the bolts are rather tricky (EGR valve pipe is the worst, can be seen sticking up at the top of photo 1), but if you tackle it step by step and ensure that you treat the parts with care (any dings / scratches on the mating surfaces = vacuum leak) then it's no drama really.

City nissan my have deemed the sensors fine, but if buildup gets so bad that it starts affecting sensors then it's too late, they should be smart enough to know this.

My Stag only has 100,000km on the clock and look whats inside, but at least after one day of fiddling I can safely say that my sooty gunk issues are over, I re-routed the breather from the drivers side rocker cover to a higher point in the intake (so oil vapour condenses and runs back down again instead of pooling in the plenum, see photo 3) and blocked the egr valve, so no more foreign crap in the intake.

I wouldn't let the issue dissuade you from buying a NEO-Di motor though as it's really only one day and the problem is solved.

Note: Throttle body is disconnected, did not need to reset ECU after cleaning, she idles smooth and low and responds well.

When you do get round to it, let me know, I may be able to pop round and lend a hand.

Edited July 5, 2010 by chad bob

[Blade NZ]

Indeed it is time consuming and some of the bolts are rather tricky (EGR valve pipe is the worst, can be seen sticking up at the top of photo 1), but if you tackle it step by step and ensure that you treat the parts with care (any dings / scratches on the mating surfaces = vacuum leak) then it's no drama really.

City nissan my have deemed the sensors fine, but if buildup gets so bad that it starts affecting sensors then it's too late, they should be smart enough to know this.

My Stag only has 100,000km on the clock and look whats inside, but at least after one day of fiddling I can safely say that my sooty gunk issues are over, I re-routed the breather from the drivers side rocker cover to a higher point in the intake (so oil vapour condenses and runs back down again instead of pooling in the plenum, see photo 3) and blocked the egr valve, so no more foreign crap in the intake.

I wouldn't let the issue dissuade you from buying a NEO-Di motor though as it's really only one day and the problem is solved.

Note: Throttle body is disconnected, did not need to reset ECU after cleaning, she idles smooth and low and responds well.

When you do get round to it, let me know, I may be able to pop round and lend a hand.

Hey Chad,

thanks again for the feedback and your offer to assist, much appreciated. I may take you up on it in the future.

It's been along time since I worked on a car motor, for the last 15 years or so it's been just motorbikes. It's not the task itself that's the problem more my time and location. Car lives in a carport as the garage is full of bikes & home theatre and the weather at the moment just sucks - as you know. I'm sure an oppertunity will present itself in the near future and as the car seems to be running fine I'm not stressing to much. It'll give me a chance to finally use my 1/2" socket set as I'd never use that size on motorbikes.

I actually just got of the phone to the service manager at City Nissan. He and I together looked over and discussed your photos and the situation. He was very good, and accommodating, and will be briefing his staff accordingly. The rest now is up to me but I will report back to them my findings and we'll see what feedback I get from them.

I must add that the 100k service was done very well and I have no complaints other than this situation. I will use them again as I found the price reasonable and the staff very good. The loan car they gave me was very good, a Qashqai (don't know why they wouldn't give me a GTR) and they gave my car a groom before I picked it up...all good.

One question for you chad, would it be possible to add an in-line filter or a catch bottle to the EGR valve line instead of blocking it off? I like the idea of re-routing the rocker cover breather but feel reluctant to block off the EGR valve as it must serve a purpose specific to the DD motors and eliminating it might cause other issues. I understand what they have been used for in the past and I a bit surprised they are still used but there must be more to their continued use. I've rebuilt L28 Z motors years ago so dealt with it all then but why are they used here. Catalytic convertors alone seem ok with normal petrol engines why do they need to recirculate exhaust with a DD motor? More research needed, or maybe you and others will have the answers.....I have always just ripped all emission gear off bikes as it just robs power and like to keep things simple but these engines are a little different!

Cheers.

[chad bob]

why do they need to recirculate exhaust with a DD motor? More research needed, or maybe you and others will have the answers.....I have always just ripped all emission gear off bikes as it just robs power and like to keep things simple but these engines are a little different!

Cheers.

Nope the EGR valve carries no special purpose at all beyond the age old exhaust gas recirculation during cold start to reduce emissions. The EGR valve on Direct Injection motors is exactly the same as the unit on any other fuel injected mill, the only difference is that in a Di motor it clogs up the damn intake!

I have had my EGR valve blocked off since my first intake clean (20,000Km ago) the motor runs just as smoothly as before and the gunk has been kept at bay (in the upper plenum at least).

The only down side is that the check engine light stays on with code P0400 (EGR valve loss of vacuum) [no duh], but I have got into the habit of resetting the ECU every few weeks and checking error codes, never bothered me none.

Oh I also forgot, another mod I did whilst amongst it was to bypass the water jacket in the intake plenum around the throttle body, it's supposed to heat up the intake on cold mornings to aid starting, but it never gets cold enough in Auckland to justify this, so all it's doing is heating up your nice cool intake charge! Nope has to go!

Edited July 5, 2010 by chad bob

[Blade NZ]

Nope the EGR valve carries no special purpose at all beyond the age old exhaust gas recirculation during cold start to reduce emissions. The EGR valve on Direct Injection motors is exactly the same as the unit on any other fuel injected mill, the only difference is that in a Di motor it clogs up the damn intake!

I have had my EGR valve blocked off since my first intake clean (20,000Km ago) the motor runs just as smoothly as before and the gunk has been kept at bay (in the upper plenum at least).

The only down side is that the check engine light stays on with code P0400 (EGR valve loss of vacuum) [no duh], but I have got into the habit of resetting the ECU every few weeks and checking error codes, never bothered me none.

Oh I also forgot, another mod I did whilst amongst it was to bypass the water jacket in the intake plenum around the throttle body, it's supposed to heat up the intake on cold mornings to aid starting, but it never gets cold enough in Auckland to justify this, so all it's doing is heating up your nice cool intake charge! Nope has to go!

Yeah, thanks for that it all makes sense. EGR just the same as it always was so no damage eliminating it. Sounds good to me and I didn't know these used coolant around the throttle body, another unnecessary piece of plumbing that we would be better of without.

Sounds like I need to get the misses to take a few days off work and run the kids around and I can get down to business (i'm sure she'll be rapped with that idea).

[o2bfit]

Nice work Chad Bob.

This has got me concerned. The issue is far more serious than simply cleaning the throttle body. Correct me if I'm wrong, but I don't think the Subaru Upper Engine cleaner will get rid any of this and isn't really worth pursuing as a regular service option.

The issue isn't isloated to the Neo DI engines, the VQ35DE has the issue but not to the same extent. From what I have seen on the web, the VQ35DE owners put a oil catch can on the left bank (from the front of the car) and feed it into the intake. Although I suspect the the EGR Valve pipe is in a different place on the Neo DI engine. I keen to do this to resolve it but there isn't much room in the engine bay.

[chad bob]

The issue isn't isloated to the Neo DI engines, the VQ35DE has the issue but not to the same extent. From what I have seen on the web, the VQ35DE owners put a oil catch can on the left bank (from the front of the car) and feed it into the intake. Although I suspect the the EGR Valve pipe is in a different place on the Neo DI engine. I keen to do this to resolve it but there isn't much room in the engine bay.

Yes that oil breather pumps out a fair bit of oil straight into the intake, there was almost 1/2 a cup of clean oil in my intake, what a silly design!

The funny thing is that the LH bank rocker cover (from the front of the car) has 2 breather hoses, one goes to the other bank (which vents into the intake via a large diameter hose before the throttle body) and the other is the trouble maker going straight into the intake, I don't see why there needs to be 2? The purpose of these breather hoses is to prevent pressure buildup, so one hose should be sufficient.

It's a bother that this is hapening on the VQ35's too, it shows that it's more down to a design fault in the intake rather than the fuel injection method, the problem is deffinitely amplified in the NEO- Di motors due to that lack of fuel vapour for cleaning though.

[X-Modcarz]

Doing the intake, plenum and AFM clean this weekend guys, together with an oil/filter change.

Wish me luck.

[Blade NZ]

Doing the intake, plenum and AFM clean this weekend guys, together with an oil/filter change.

Wish me luck.

Absolutely! Good luck and we'll await your results. Interested to hear what condition it's in so keep us posted.

Cheers!

[Spong]

Doing the intake, plenum and AFM clean this weekend guys, together with an oil/filter change.

Wish me luck.

Let us know how many km's your car had done, and maybe some photos of what it looks like please?

[X-Modcarz]

Well, I have pulled it apart and it ain't pretty at all. Thats probably because cars done 162000kms already and never ever been opened. I have pulled out the upper and lower large plenum. I also had to pull out the lower block that goes under the lower large plenum. The chambers going to the cylinders are also filled with gunk.

I am planning to wipe as much as possible with cloth dipped in brakeclean wrapped around a screwdriver. This means that some of the gunk will go into the cylinder. Now I am not happy with that but I don't have a choice. I will take the spark plug out and try and use a compressor to blow the gunk out as much as possible.

Let me know what you guys think about me doing this?

Ok, I just scrolled up and saw the pics Chad posted. Mine is exactly like that. So I will just have to bite the bullet and clean it out. I have only driven the car for 50kms now and felt it was slow off the mark from a stand still but picked up speed as it accelerated. Am keen to know if this makes a difference.

Edited July 9, 2010 by X-Modcarz

[Ant]

Chad Bob - you're the man, awesome pics. I have a funny feeling I now know what is causing a bit of smoke to come out the tailpipe of my car at high RPM - must be when the valves open a bit further and some of that crap gets blown out.

Does anyone know if any workshops in Auckland can do this kind of thing without it costing an arm and a leg? And who could do it without breaking or ruining anything? Would like to get mine done but I think this is a bit beyond my basic DIY skills...