Nissan Gtr High Idle And Throttle Body Fix

[GTRPSI]

Nissan GTR throttle body and high idle fix.

The Nissan Skyline GTR is known to sometimes have a high idle appear especially on vehicles being boosted for extra power.

In extreme cases a misfire may also develop off boost in my case up to 3500rpm which would then disappear once boost was hit, all the way to the red line.

The problem is often the standard factory paper gaskets getting brittle and combining this with high boost pressure, the brittle gasket will crack leading to air leak at the join, resulting in a high idle.

A temporary fix is to adjust the idle screw till you run out of adjustment.

To do this, disconnect the plug going into the idle speed control motor to eliminate the ECU's ability to control the idle and start the engine. Next to the idle control motor is a screw that can be turned to adjust the amount of air entering the engine.

Turn off the engine and reconnect the plug back in so the ECU has control. If the engine speed has gone back up again after starting, take off the passenger side kick panel to expose the ECU. On the side of it is a variable pot that is a fine tune of the RPM, do not turn it too far to avoid damage to the pot.

If that failed to bring the idle down enough, chances are good that one of your hoses is cracked and leaking or your throttle body gaskets are gone.

After removing the throttle bodies and the intake manifold that holds them under it on the head, take a look at the gaskets.

This is what your looking for.

Cracked gaskets.

Dirty looking sections where air was getting in.

Discoloration on the aluminum surfaces where there was no or poor gasket contact.

After cleaning all the old gasket off there are a number of ways to get a new seal.

1/ Replace them with new paper gaskets. Great if your not running high boost, coat the paper with a good sealer like Hylomar to help with the seal.

2/ Steel replacement gaskets such as those made by companies like Tomei. The problem here is that being steel, they will not blow however the seal is not the best and may still leak slightly.

3/ The racers trick. A nice thin even coating of "blue" silastic.

While the throttle bodies are off you may want to clean them.

If you look inside where the throttle butterflies are you may see a black coating inside the throttle bore.

DO NOT clean this off, its a black silicon coating used to help seal the butterflies, use a carby cleaner spray and blow it clean with compressed air.

Sometimes you may look and find its too late, where the previous owner or mechanic did not know better and cleaned the seal all off.

If you didn't find a leaking gasket but all the black sealant removed off the throttle body, chances are that the leak caused by the sealant missing is the reason for the high idle.

This is an example of no sealant in the throttle bore, actually you can see some black marks of where it use to be.

Most people at this point give up and buy new ones from Nissan for over $1200 or try their luck sourcing second hand ones that have not been damaged by cleaning.

What i did was a reset all the throttle stops to keep the butterflies as closed as possible, but not so far closed as the butterfly would bind in the bore. To do this undo the throttle stop adjustment on each throttle plate and let the butterfly close till it binds in the bore.

Then turn the adjustment screw in till it contacts the lever for the butterfly.

Now give it 1/3 of a turn in and check to see that the butterfly can open and close without binding closed in the bore.

Should one or more throttles bind, redo them all to 1/2 a turn in and test again.

The stop adjustment screw.

Now to reseal or reapply the black factory coating that seals the butterflies.

Take note of the direction the butterfly open, on one side from the top, and the opposite side from the bottom.

You want to apply a thin coating of blue silastic to the opposite side of the throttle bore that the butterfly turns to.

One side

The other side

Once the silicon has hardened to a slightly rigid consistency (1/2 hour), operate the butterfly to break the seal, otherwise the butterfly will get stuck in the bore.

Do this a number of times to make sure things don't get stuck.

After the silicon has hardened, hold the butterfly up to a light and look for leaks, if any are found add a little more to this area.

When finished rub off any excess off the butterflies so any sealant only remains on the throttle bore.

There you just saved over $1200.

Now just reassemble and readjust your idle as explained at the beginning of this write up, there should be heaps of adjustment now.

[heller44]

Nice writeup. Suggestion, Nitto metal gasket set as an option replacing the tomei or hks, a reasonable amount cheaper. Not sure wether I was meant to but I used hylomar spray on the gaskets before fitting.

Just finished replacing my intake manifold and throttle body gaskets due to paper ones being blown out, good luck with getting everything off and then back together without a lot of swearing.

[mattR32gtst]

Metal gasket me thinks is the way forward, great write up though this has helped with a little problem of mine

[gotRICE?]

Double yew tee eff?

[noone]

Can anyone confirm this actually works??

the throttle body repair that is not the stupid interview techniques

[topspeed.ua]

Wow this helps!

[DVS JEZ]

i have tried adjusting aac, disconnecting aac, screw on ecu, vaccuum leaks, adjusting the throttle stops etc etc.

i found that disconnecting the throttle linkages the idle dropped to 850rpm, so i kept engine running and adjusted the linkages so the idle didnt change, then i adjusted the aac valve screw to bring idle to 950rpm.

[lukesz]

is there a DIY on how to take the intake plenum off? im struggling to get mine off

[JiN_MaN]

I would have loved a DIY for removing the Plenum as well,

I just handed over $550 to have this done If only I had seen this earlier.

Edited April 20, 2010 by JiN_MaN

[omygod]

Ok, Ive got the tbs were in front of me...Im cleaning em....

So I figured, has Nissan *really* put a coating in there to seal up its

throttle body??

So I dig deeper....nothing in the factory manual about adjusting these

flaps or replacing a coating or whatever. Just a very comprehensive

page about setting the optimum length for linkage tierods...clue 1

So I dig deeper...wouldn't there be a replacement can of goo from Nissan

for this perhaps maybe 88 dollars for a 150g of this stuff?

I mean the "black coating" comes right off with your hand....no harsh acids

or 190 proof grappa either....

Well Tomei have a throttle coat...A quick glance at Tomei's site tells us the

entire procedure of putting goop on....apparently it improves throttle response

(literally to pedal response).

http://www.tomei-p.co.jp/_2003web-catalogu...hers_gauge.html

It says NOT to put it on the main body...only the flap. Curious, so if it does any

sealing it is relying on the throttle flap to do the sealing...Makes sense, well thats

what the job of a throttle flap is when closed! However how big a gap is this meant

to close? Its not intended for that primarily....Btw primary ingredient is

molybdenum disulphide.....clue 2

From what I can see, some people are over-zealous with their cleaning

attempts, flexing the throttle shafts and somehow damage the throttle shaft seals

on the sides...or leave some dirt right up the shaft seal area which acts like a wedge

holding the tb open slightly....These are delicate precise things...

Well then a good clean and a reset (if required is to be done). It is ideal that

all the flaps seal. Also note that there are THREE air bypass routes

for idle control. Two in the IAV (a bleed screw and the solenoid valve itself and

a supplemental air path in throttle body 1.

So it stands to reason that:

- The factory tbs need to be clean to operate properly.

- There is no sealant that nissan use at the factory. There is no empirical evidence to

demonstrate its being applied aftermarket.

- Cleaning the throttle bodies does not result in idle problems however

improper cleaning may cause idle problems.

The throttle stop screw for each throttle body requires some time to

reset...not long...just a few minutes to get the position right. It pays to

use some moly disulphide grease (CV Joint grease) on the flap edges and the

stem while setting it. Once set, there should be NO gaps visible....these

are precision NC machine surfaces and hardened....flaps are batch stock

and are "best fit" however are matched to each bore and adjusted to seal.

Of course there are going to be factory errors, minor warping due

to peak engine temperatures...so perhaps some correction is required...

So moral of story....

1) Clean well, with toothbrush, metho, perhaps a zap or two of throttle

body cleaner for stubborn bits....

2) Check seals.

3) Lubricate.

3) Reset stops (if required).

Then follow the linkage tierod setting procedure in the RB26 manual.

(In R32 GTR factory manual it starts on page EN37).

Then final idle adjustment should be done using the IAV bleed screw.

[XRATED]

For peoples information-

The shaft seals in most 32 and 33 rb26 ITB's push out and leak under higher than stock boost too... Most of the seals I've seen are dry and cracked. They don't usually cause vacume leaks at idle, but it dose happen.

Here's the kicker- Nissan don't sell the shaft seals seperately...

J.

[omygod]

Ok I have to add to my last post. It seems not all throttle bodies are created equal. In my batch,

some have poor seals on the edges of the throttle flap and some are perfect. I suspect this is a

messup on Hitachi's part..and Nissan fixed it up with their magic sealant they dont want to talk

about...

After checking the tbs, Ive found that only 2 out of 3 sets were "letting light through" and could not

be adjusted to be shut properly...

I've used a slightly evolved sealing procedure to the one described by GTRPSI:

1) Lightly line the bore with moly grease (to stop the throttle getting stuck or damaging the

bore during step 2.

2) Reset the throttle stops until the flap has resistance in the bore and then

wind it out 1/3 turn or more until the bind is free.

3) Then clean bodies again with methylated spirits

4) Place a 1.6mm spacer between the throttle stop and the arm causing the

throttle flap to be open slightly more.

5) Mix up some RTV sensor safe silicon with some butane (polar solvent) to thin it

down to paint consistency...

6) Paint a light coat on the body near where the flap contacts on the opposite

sides of the flap AWAY from its movement.

So you dont want the flap moving into silicone but moving away from it.

7) Let set...then using a scalpal, cut close to the flap and then free the throttle.

8) Clean the throttle flap and any excess

9) Now remove the spacer from the throttle stop....

The flap will close against the silicon and have an amazingly tight seal due to

the resistance on the flap...

Then the linkages get reset according to the r32 manual...

This then gives the IAV a much larger degree of control over idle.

With my cleaned bodies and reset WITHOUT the sealing, the lowest I could get

the idle was 1000rpm. Not bad but not good either.

The sealing required the IAV Idle fine adjustment screw to have a dramatic

effect on idle...

[GTRPSI]

Just an update, our GTR still idles at 950rpm solid since this mod, the silicon is holding well in the throttle bodies and doing its job.

Lots of adjustment left still in the AAC valve, i could drop the idle down as far as id like to if needed.

Edited May 12, 2010 by GTRPSI

[xfixiate]

Pics have dropped off, any chance of a repair?

[Trifer]

Just a quiery, i found that 2 out of the 6 throttle gaskets on my rb26 had cracked through. Causing an air leak, BUT i never had any idle issue.

The only issue i did have before doing the gaskets was that i would smoke screen the people behind me under heavy acceleration with unburnt

fuel. The idle would still sit on 950 rpm. Since replacing the genuine paper gaskets with tomei steel ones, and cleaning around the throttle plates, my idle

went to 2000rpm, so i then looked at the aac valve ajustment. Which was screwed all the way out, screwed it all the way in and the lowest it

goes to is 1600rpm. I was then told by nismo performance that u have to re-adjust the linkages. I took them off the accelerator link, pushed toward

the head (which would close the throttle plates if the linkages where too short) and no change in idle. I have checked for air leaks, which i have

none!!

So...

First question if someone can help me is:

Why didnt my idle go higher with the gaskets broken??

Secondly:

Is it possible i created the air leak in-between the throttle plate and housing by cleaning them??

Thirdly:

Is the Tomei Throttle Coat hard setting??

and lastly:

How sure can we be, if i do seal the throttle plates with either rtv or tomei coat, that my idle will go back to normal, and if it doesnt, wat else can be a factor??

Ps. Instead of the rtv sensor safe silicon, wouldnt the tomei throttle coat be better?? Plus being meant to be used on throttle bodies??

Pps. Drove the car with high idle, no more unburnt fuel. So at least one problem was fixed.

Thank you all in advance

[GTRBANDIT]

I have the same problem. If anyone is interested in fixing this problem on my 32GTR name your price and I'll get it started on as soon as possible.

i'm located on the goldcoast. 0420907784. thanks.

[Trifer]

GTRBANDIT are you having the same problem as in you took off your collector,

replaced the gasket and cleaned the throttle plates and bore and removed the

carbon??

I'm just curious, because if i solve my problem, i'll be able to help with yours.

But i'm located in Melbourne

[DVS JEZ]

NEVER CLEAN THE GTR THROTTLE BODIES!!!!

Now that that is said unfortunately u will need to remove it all again and buy some tomei throttle coat. This throttle coat reseals the butterflies which u have "cleaned" (/ruined).

Theres a coating in the throttle bodies which looks like carbon build up but is actually a sealant.

Whats happening now is there is a gap around the butterflys letting in air to the engine just as if u are holding the accelerator slightly.

[Trifer]

Thanks DVS JEZ I figured that out. And fixed the problem.

Thing is. I now have a better response with the throttle coat

than I did with the factory sealer. So it was a bad judgement

which turn out better for myself.

[xfixiate]

I used the Tomei throttle coat, tied the butterflies open to let it air dry

now the throttles wont close. have tried opening and closing to see if it would "wear" but no luck.

Is there something that will soften the coat, or do i need to remove and start again?

How to do?

Thanks

John