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

[chad bob]

Hey guys,

I was just wondering if anyone round here has a 300GT or 250GT V35. Reason I'm asking is that they're Dierct Injection and like most direct injection cars on the market (including my stagea) they may be in the process of or already on the way to fish town.

So I have been hearing a few complaints recently concerning 'Gasoline Direct Injection' engines, particularly concerning vehicles from Toyota, Mitsubishi and Nissan. GDI has become rather popular in late model cars recently, notably the Mitsy 'GDI' and Nissan 'NEO Di' which seem to be the most prolific of the GDI vehicles, european examples are the VW 'FSI' system and also Opels new GDI system which is now widely used on late model vehicles without advertisemsnt. Now the complaints are mostly concerning poor fuel economy and multiple sensor failure with expensive repairs.

This is strange because amongst a notable increase in power over similarly designed SFI (sequential injection) and Multi point injection motors, GDI motors usually have a rather impressive factory fuel consumption rating which makes them rather attractive to buyers. These buyers are often disappointed when they get to the pump with their new car only to find that it's been sucking fuel like a v8.

It is rather hard to find information on why these NEW cars are costing so much to maintain and using more gas than expected, the funny thing is that performance also drops rapidly as the fuel consumption rises.

Instead of providing an explanation, car companies remain tight lipped and owners get fed up with mechanic bills.

So given the listed issues:

-Poor fuel economy.

-Decreased performance.

-Injector and sensor failure.

What is going on?

What seems to be a constant in all examples is that problems start occurring once the vehicle millage passes 60,000Km. I discovered this while trying to research information on the VQ30DD motor in my Nissan, all the info I could find was in Japanese, but I did find the above information relating to GDI vehicles in general and also from personal accounts of friends with GDI vehicles. So I thought that since my car was GDI and was also passed that 60,000Km milestone, then it must be showing signs of whatever ailment has been plaguing other GDI motors.

I thought that since the difference between GDI and MPFI motors was on the induction side, I would start there. It didn't take long to find the culprit, in fact as soon as I opened the intake manifold it was all too obvious.... SOOT everywhere! it was like black snow coating everything from the port side of the throttle butterfly to the valves, it was 1mm thick in places and not unlike the oil residue found inside the crank case of an old 2stroke lawn mower. This was a shock and totally not on for a car that was other wise in 'as new' condition, it took a can of degreaser and a water blaster to get the manifold back to 'as cast' condition, I then set about looking for the cause.

The cause too was rather obvious, modern engines are being fitted with any manner of emission reducing gadgets, the most popular being the classic rocker cover vent breather and the horrible EGR or 'exhaust gas recirculation' system, both of these are designed to 're-burn' oil vapour and un-burnt fuel that would otherwise be vented into the atmosphere. When used in conjunction, the EGR and rocker cover vent supply both dense and water rich fuel soot and oil vapor back into the intake where they mix to create that lovely sooty crud, most of which goes back into the engine harmlessly as it's supposed to do, but much of it winds up stuck to the walls of the intake.

Now in a normal SFI MPFI (sequential, multi point fuel injection) fuel is injected into the intake piping right behind the valves, 'Sequential' systems are designed to only inject when the valves are open, but there is still deflection and fuel vapor ends up joining the EGR and Rocker cover emissions back up in the intake, this is good because the fuel mixes with the vapors, dissolving deposits and making them less likely to settle.

Of course since GDI engine injectors are inside the combustion chamber, on the other side of the valves, this means that there is nothing to stop the buildup of deposits, hence the GDI intake becomes more and more choked until the motor starts running rich and eventually large chunks of 'crud' become dislodged and end up passing the valves and become the proverbial 'spanner in the works' and this stuff does buildup into rather hard little lumps in places which wreak havoc on O2 sensors and injector nozzels.

There you have it, the cause of our problems, since the car companies dont care about cars out side of their warranties, car owners are left scratching their heads and local mechanics keep this to themselves because business is booming!

The only solution is, as soon as you notice your new ride becoming more thirsty, find a friend who knows motors relatively well or talk to your mechanic and ask them to check your intake once every 20,000Km or so as a standard servicing procedure. My car was not noticeably less powerful but it was using a little more juice than expected, hence my adventure into crud city.

If you don't want to pay extra for an intake clean on every second service, there is a way of making your GDI vehicle crud free for life!

Have a catch can installed on your rocker cover breather, this is a tank or 'can' installed in the line linking the rocker cover to the intake, vapors passing through the tank settle and this is where the oil deposits remain, leaving only clean dry air to enter your intake. In many cases this will only reduce the buildup slightly as there is still the deposits from the EGR valve, to fix this, I found an old exhaust manifold gasket and trimmed it down to fit the EGR pipe flange so replacing the original gasket seal, this creates a 'blanking plate' that effectively prevents the EGR from functioning but allows you to leave the EGR plugged in so that the ECU doesn't pick up any errors. These procedures will keep your intake crud free for life and will only slightly affect your vehicle emissions, the extra emissions produced by removing your EGR valve will be offset by the fact that your car will now run cleanly and efficiently without sucking down loads of fuel and smoking as the engine over fuels due to reduced breathing.

A friends Mitsubishi 2000cc RVR was using 16L/100Km on average, the intake looked like a smoker's lungs when I got it off, the original 45mm intake was nowhere near that in diameter due crud, go figure.

[zei20l]

there are carbon cleaning services (via mechanical workshops) that perform what ill call 'non-invasive' carbon clean outs. i think they flush the injectors with a fluid, and also a cleaning agent into the intake piping to remove all the oil build up there, and also in the combustion chamber. im not sure how effective it is, but people have had performance increases (probably close to factory) and increased fuel economy.

i dont know how well it would fare with Di motors, but i guess oil/carbon build-ups are the same in pretty much all motors.

im surprised to see EGR on a fairly recent motor like yours. i thought they stopped using it in the 90s when 3-way cats became more cost effective and fuel management was better?

as for crank case ventilation, its sucks that ALL motors suffer from this necessary evil.

[chad bob]

That sounds like a good idea, in the US they sell Direct injection cleaning kits with a spray for the manifold and a fuel additive.

As far as the crank case vent, I'm going to install a catch can to take care of that.

[zei20l]

ahh yes ive seen after market kits for this purpose, i think you stick the brake master cylinder vacuum hose into a bottle of fluid (i think even water will work) and that is sucked into the intake, i guess it vaporises and takes all the crap with it to be burnt. and the fuel additive would take care of the injectors.

i wonder how effective this option is?

and yup, catch can FTW!

[Oaksey]

I think you will also likely find that on cold mornings the car will run a lot more smoothly on startup, at least a previous car of mine did when the recycling was taken out of the equation. I'm guessing less fuel is burnt while the engine is getting up to normal operating temperature and the engine management doesn't take into account what is getting recycled and put less fuel in as a result, meaning normally the engine gets too much fuel until it is up to normal temp.

[zei20l]

the engine will run rich on a cold start anyway, they are programmed to do that. getting it up to temp as fast as possible (for emissions reasons) but its not severe compared to the 'normal' map

[chad bob]

Sorry for bringing this thread back to life but I've stumbled onto a winner for all owners of Direct Injected Nissans!

'Subaru Upper Engine Cleaner' you heard me, effectively it's the stuff that was mentioned previously, it gets sprayed into the intake as the car is running and it removes ALL carbon buildup and varnishing from the intake manifold, valves and combustion chamber.

Cans of this stuff is supplied with new Subaru service kits as a reccomended service item. All Subaru dealerships in Australia and NZ hold stocks of this stuff and it'll cost about $20 per can give or take a couple of squid.

It's designed to take the intake tract of the motor back as close as possible to how it was when it rolled out of the factory. Probably not reccomended for HIGH millage cars in which case the carbon deposits are the only barrier stoppng the rings from passing oil.

Well I'm doing the dance.

[xscape237]

That subaru stuff is basically the same as what the yanks call "sea foam". Do some googling it could be interesting.

FYI i tried it on a 350,000+ KM honda civic (original motor) and it made a noticable difference. Better idle and seemed to accellerate with more smoothness, perhaps even gained a little power down low.

Also tried it on a 60,000 KM 2JZGTE and it was a waste of time.

[Touge Kyousou]

Uhm, someone able to clarify:

Will carby cleaner do the same as the subaru upper engine cleaner... i've known about the sub. upper cleaner for years but when i first bought my V and my mech was changing the spark plugs, he noticed the intake was coated in a film of oil, so he used a bit of carby cleaner.. engine was indeed smoother afterwards etc.

I've used the carby cleaner afterwards myself a couple of times and it's worked a treat.

[chad bob]

I think the difference between the Carb cleaner and the Poobaru cleaner is that you dont need to disassemble too much to use the latter. Just spray it in the intake with the air filter removed while the cars running.Carb cleaner is more of a strip the intake and clean each part deal. (I did this last service, it was most average and took a couple of hours)

Edited November 26, 2009 by chad bob

[Easy Tiger]

Would this Subaru stuff fix fouled injectors?

[V35_Paul]

Would this Subaru stuff fix fouled injectors?

have you tried fuel treatment injector cleaners? Buy them at any servo

[Easy Tiger]

have you tried fuel treatment injector cleaners? Buy them at any servo

Yeah I tried a bottle but no difference. Maybe i need to try winns spit fire?

[xscape237]

Would this Subaru stuff fix fouled injectors?

I doubt it. It doesnt go through your fuel system.

You spray the stuff into your intake plenum.

[Daleo]

Would this Subaru stuff fix fouled injectors?

You would be better off removing the injectors and having them professionally cleaned. Not that expensive and they'll flow test them so you know you're putting back good gear.

[chad bob]

^ What he said, I had it done, only costs $20 per injector usually.

[Spong]

^ What he said, I had it done, only costs $20 per injector usually.

I know this is a very old thread, but hoping you're still monitoring this Chad Bob. I saw your similar post re; Nissan Di motors at europort.org.nz a few weeks ago, soon after my 2006 RX250 FOUR M35 was on it's way to NZ. It sure put a dampener on things. My car has landed, has 84K on the clock and runs very well at this stage. This weekend, I opened the throttle butterfly, and sure enough, I could see a coating of around 1mm of black death from there in. I guess I should let loose some Subaru upper cycling cleaner. How many bottles do I need? Do you recommend 1/3 in the petrol tank, 1/3 in the crank case, and 1/3 in the brake booster vacuum line as someone on Youtube mentioned? Sorry I couldn't PM you. I need something like 10 posts before I can do that.

[chad bob]

Hi Spong,

As a bit of an update I have completed 26,000 trouble free Kilometers in my VQ30DD Stagea. As you have just received the car, I would recommend pulling down the intake, removing the big plenum and giving it a good water blast on the driveway, the rest of the gunk can be cleaned off with brake and parts cleaner. I say this because there will be a lot of buildup at this stage if it has not been addressed offshore (unlikely). When you put the intake back together, try to put together a blank off plate for the EGR valve (metal pipe coming from intake just past throttle), it's rather simple, just two holes, I used an old exhaust gasket that I had lying around, this should slow down or prevent the buildup from occuring in the future, it'll throw a check engine light but I ignore this or reset the ECU and it stays off for a month or so.

I have made a habit of pulling the lid off of the plenum once every two service intervals just for a checkup, but so far the gunk has not returned.

Regarding the Subaru upper engine cleaner, there are instructions on the can, follow them and you'll be fine. I'm not sure how well this worked as I did not open the plenum after application.

So this issue isn't really the bugbear that the mechanics get worked up about, the intake is a doddle to remove and the rest is common sense.

Edited May 31, 2010 by chad bob

[Blade NZ]

Hi Spong,

As a bit of an update I have completed 26,000 trouble free Kilometers in my VQ30DD Stagea. As you have just received the car, I would recommend pulling down the intake, removing the big plenum and giving it a good water blast on the driveway, the rest of the gunk can be cleaned off with brake and parts cleaner. I say this because there will be a lot of buildup at this stage if it has not been addressed offshore (unlikely). When you put the intake back together, try to put together a blank off plate for the EGR valve (metal pipe coming from intake just past throttle), it's rather simple, just two holes, I used an old exhaust gasket that I had lying around, this should slow down or prevent the buildup from occuring in the future, it'll throw a check engine light but I ignore this or reset the ECU and it stays off for a month or so.

I have made a habit of pulling the lid off of the plenum once every two service intervals just for a checkup, but so far the gunk has not returned.

Regarding the Subaru upper engine cleaner, there are instructions on the can, follow them and you'll be fine. I'm not sure how well this worked as I did not open the plenum after application.

So this issue isn't really the bugbear that the mechanics get worked up about, the intake is a doddle to remove and the rest is common sense.

Hey Chad Bob, thanks for the update. I've also just got my stag, a 300RX.... and now a can of Sub U.E.C. so I'll be sure to give it a good going over (when the rain stops). Good to hear you've been 26k without probs.

[chad bob]

Hey Chad Bob, thanks for the update. I've also just got my stag, a 300RX.... and now a can of Sub U.E.C. so I'll be sure to give it a good going over (when the rain stops). Good to hear you've been 26k without probs.

I pulled off the engine cover and used the vacuum hose on the left of the plenum (master cylinder side not intake side) I thought this hose would be the most direct for getting the cleaner into the turbulent air.