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

[scotty nm35]

At least you know where the plugs are now.

[Roachy94]

Who knew that black plastic on the engine with writing on it came off. Learn something new everyday

[0li3te]

I was going to check the plugs but it got a bit late

[scotty nm35]

This jogged my memory to post up these pics of the VQ25det plug, DD plug and whatever plug the last mech installed into the 25DD I have here.

I did some research into the quad ground plugs, it seems they are inferior to the iridiums anyway.

[projects]

so you're saying scotty I'll be able to get away with some standard iridium's in my vq25dd now?

[scotty nm35]

Yep, I would go with a set of LFR5AIX. No need for quad earth plugs according to that video, all the extra earth lugs do is slow the burn down. You will only get one spark at a time, not 4.

[projects]

ok so i thought my P0400 fault code was due to the wrong resistor being in the temp switch position. So yesterday i swapped out the 42kohm resistor i had for a 10Ohm 5watt resistor. Cleared the codes and then started the car. 5 seconds after starting i get a P1401 EGR temp sensor. So i tried a 10Ohm 10watt resistor. same deal.

Looking into the USA infinity sites for the VQ30dd altima and maxima, a lot of guys have used 100kOhm .25watt resistor. So that's my next one to try. Once i get this i'll let you all know what size resistor i used.

[scotty nm35]

Why don't you use a varistor? That way you can fiddle to your hearts content.

I am guessing you will need to switch the resistor into the circuit when the egr valve opens, using a relay...

[10 4]

Hi, possibly picking up a 300GT tomorrow (deposit paid).

Wanting to do this just a precautionary thing.
If I show my mechanic page 3, he should know what to do..?

Kind of annoying... Tempted to get a 350GT (sedan) instead..

[scotty nm35]

I have done a few carbon cleans now, prick of a job. He will need to strip it down to the heads and clean the plenum and runners, then clean around the intake valves. A few of the valves will be open so he will need to rotate the engine to make sure no crud enters the bore when he cleans inside the head runners.

I use gasket stripper soaking overnight and a toothbrush and scraper to loosen most of the carbon, then a large syringe to suck most of it out.

[10 4]

Sounds like the bill won't be cheap...
Also, 95 or 98 RON fuel? Will it make a difference?
Its mum's car so won't ever get driven hard.

[PN-Mad]

Won't effect the fouling problem, thats related to EGR I believe.

But DD motors run quite high compression 11:1 or around that. 98 would be advisable.

[scotty nm35]

Even with the egr blocked off the valve overlap will cause carbon to build up around the intake valves, as there is no fuel spraying on them to keep it clean. It's the main issue with direct injection engine design.

[10 4]

Thanks for the replies, will stick to 98, do the clean, see what mech says about blocking off EGR & putting in a resistor (no chance of an illuminated fault light on the dash on mum's car.. haha).

[JZX91-2JZ]

Did the plenum clean last night on my mums 250gt with 102K on the clock. It was filthy!

Was a pretty straightforward process to strip and reassemble everything. To clean the components I used a product by Lanotec called powawash which is a quick break degreaser/parts washer and some steel wool to clean it all up. Once everything was back together the car ran a lot smoother and was more responsive. Today I followed up by using a can of threebond upper engine cleaner (subura upper engine cleaner) just to make sure she would be sweet.

[scotty nm35]

So you only did the cover? You need to do the lower runners, the cover will make fark all difference.

Don't bother with the 3bond, it is like pissing in the wind. Just remove the parts, and soak them in degreaser, then use tooth brushes or whatever you can to clean the runners. I used a scourer on a metal rod but whatever works for you.

The ports on the head are the hard part to clean, you need to make sure the valves aren't open on the ports and clean them out thoroughly before rotating the crank, or starting the engine. I use a large syringe to suck the cruddy degreaser out usually, but you will need a few of them...

[gtrtech]

So you only did the cover? You need to do the lower runners, the cover will make fark all difference.

Don't bother with the 3bond, it is like pissing in the wind. Just remove the parts, and soak them in degreaser, then use tooth brushes or whatever you can to clean the runners. I used a scourer on a metal rod but whatever works for you.

The ports on the head are the hard part to clean, you need to make sure the valves aren't open on the ports and clean them out thoroughly before rotating the crank, or starting the engine. I use a large syringe to suck the cruddy degreaser out usually, but you will need a few of them...

What gaskets, seals are required to do this job properly, if any?

Looking at doing this on my 300GT soon enough if it doesn't sell 1st.

[scotty nm35]

If you don't damage the gaskets you don't need to replace anything. They are steel gaskets, I usually spray a bit of Hylomar on them just incase on re-assembly.

It's a prick of a job, very messy and at least 10 hours work to do properly.

[Spong]

We had our 2006 Stag with VQ25DD decarbed at 120K by our local Nissan dealer just over a year ago and it came back with an intermittent miss at idle progressing to a nasty stagger on acceleration a month or so later. It was far worse than before we took it in. It went back to them 3x times and nothing they did fixed those problems and they investigated all sorts of stuff including coil packs etc, but they were sure it was nothing they'd done. Eventually, several months later, after losing all faith in them, we took it to a specialist in modern engine problems. It didn't take long for him to find that one of the new spark plugs Nissan had fitted had a cracked insulator, and was tracking, and was obviously caused when installed. By that time, I'd had enough of the petrol bills, and the lack of expertise by the local agents, so it was sold. I'd recommend staying well clear of the 250DD and 300DD if you can. Apparently injector failures in these motors are common and expensive too - around $3K upwards.

[gtrtech]

If you don't damage the gaskets you don't need to replace anything. They are steel gaskets, I usually spray a bit of Hylomar on them just incase on re-assembly.

It's a prick of a job, very messy and at least 10 hours work to do properly.

Thanks for that. Not looking forward to it but at 160K on the clock it may well be time. I'm presuming it's never been done.