Cleaned Throttle Body, Now Revs High

[andy65b]

ahhh can they not be cleaned

and what goes faulty about them??

"The PCV valve is a spring-loaded valve with a specific orifice size designed to restrict the amount of air that's siphoned from the crankcase into the intake manifold. This is necessary because air drawn through the valve from the crankcase has a leaning effect on the fuel mixture much the same as a vacuum leak. So air flow through the valve must be controlled within certain limits. At idle, air flow is reduced because little blowby is produced. When the engine is cruising and vacuum is high, airflow through the PCV valve is at a maximum to purge the blowby vapors from the crankcase."

The more I read on this the more I think it is the cause.

I have also read about it causing rattling noise in the engine and I have that.

[RS4StagMan]

Don't know if this helps but the RB25DET powered Stageas/Skylines have an idle control valve screw on the intake manifold itself which can be adjusted to adjust the idle.

In addition to this, the R34 Skyline/Stagea ECU's have an idle control screw (or pot) on the side of the actual ECU.

MN35 (V35)?? I/m not sure. If you can get your hands on the workshop manual like the below one, it should tell you all you need to know. Even the V35 Infinity USA spec one should be OK for what you want to know.

http://www.onlinefreeebooks.net/automotive...1v35u6-pdf.html

http://www.tradebit.com/filedetail.php/654...-service-manual

[Pete82]

Hello,

RS4StagMan - Thanks for you comments, the RB25DET has a idle air control valve, The VQ35 doesnt, it uses the throttle body to control the idles air.

I took the car to Main North Nissan (Adelaide) this morning, when they plugged the consult on to it, they could only acheive the same results with idle air volume learning as i could (800rpm), and yes consult couldnt get it to hold the learning either.

When i got home, i pulled the throttle body appart. There is nothing interesting in there, there are the potentiometers (throttle position sensors) and the motor.

The screw does nothing but preload the return spring, which is set in the factory.

DO NOT ADJUST THESE SCREWS.

ANDY65B - good work on the PCV, will have to try that.

ZEI20L - I havent changed the plugs, the car has only done 62,000, and when i checked them at 60,000 they were fine.

Cheers

Pete

[Pete82]

Hey Andy,

Because the PCV is before the throttle body, it still shouldn't be effecting the high idle, (i know you said you hose has no leaks) because it is the air that is getting past the butterfy valve that is making the idle high.

These butterfly valves need to close more, which isn't happening to make the engine idle lower.

Just a thought anyway.

Cheers

Pete

[andy65b]

Hey Andy,

Because the PCV is before the throttle body, it still shouldn't be effecting the high idle, (i know you said you hose has no leaks) because it is the air that is getting past the butterfy valve that is making the idle high.

These butterfly valves need to close more, which isn't happening to make the engine idle lower.

Just a thought anyway.

Cheers

Pete

On the M35 the PCV returns to the manifold after the butterfly so this could have some effect on the idle. I have attached a picture of my engine bay with the 2 ends of the pipe from the PCV marked with a red arrow.

I did some reading this afternoon through my good friend Google and one of the common problems of faulty PCV's is idling problems.

I have also attached a photo of a V35 engine (thanks BLISTC) and I have put in a pointer at the PCV hose where it attaches to the manifold. After the butterfly. I can not see where it comes of the engine but I would think it would be in a similar position to mine.

There is some basic logic to this but it is hard to explain briefly. All I can say is that I have ruled out any electrical fault and as no trouble codes are being shown the fault has to be some thing mechanical that is not monitored.

Another sign of the PCV being faulty is oil leaks. I know I am starting to get some oil seam on some gaskets.

Cheers

Andy

Edited July 9, 2009 by andy65b

[Pete82]

Hi Andy.

That is not the PVC in the photo of BLISTC's engine bay, that is the Brake booster vacuum line.

The PCV hose comes from the back of Bank 2 cam cover, and feeds in before the throttle body.

Cheers

Pete

[andy65b]

Hi Andy.

That is not the PVC in the photo of BLISTC's engine bay, that is the Brake booster vacuum line.

The PCV hose comes from the back of Bank 2 cam cover, and feeds in before the throttle body.

Cheers

Pete

Have you got the G35 manual.

In that it shows that there are 2 hoses that come from the motor for blow by. 1) before the throttle body as you have shown and 2) after the throttle body into the manifold and this is the one I am referring to and has the PCV.

I have attached the diagram and info from the manual.

You will see the PCV is on the right bank of the motor (left bank on this diagram). If the one I have pointed out is not it then it is another one some where near it.

Cheers

Andy

Edited July 9, 2009 by andy65b

[zei20l]

nice work andy!

if i decide to try this on my car over the weekend (depending on rain) ill give you a call and we can do your car too if you want

[andy65b]

nice work andy!

if i decide to try this on my car over the weekend (depending on rain) ill give you a call and we can do your car too if you want

Yes, I want to clean mine at least to see if it improves things before the new one goes on.

How is that garage looking?

[zei20l]

the garage can be used mate, i found my work light on the weekend so i guess whenever. ill let you know when im available after i speak to the mrs, will probably be sunday tho at this stage. got a photo shoot on tomorrow then bruno in the arvo.

and i got the fiat in the other garage too! i did good work, anna's happy lol

[andy65b]

the garage can be used mate, i found my work light on the weekend so i guess whenever. ill let you know when im available after i speak to the mrs, will probably be sunday tho at this stage. got a photo shoot on tomorrow then bruno in the arvo.

and i got the fiat in the other garage too! i did good work, anna's happy lol

Do you want to borrow my "Mankini" (Borat) for the Bruno? LOL (it is so wrong)

Sunday would be good. I'll but some carby cleaner.

[zei20l]

i have carby cleaner/degreaser mate lol like 10 cans of it!

[Pete82]

Hey Guys,

I have managed to get the car all up and running correctly.

Idle Air Volume Learning procedure all complete.

ANDY65B - i followed on further from you PVC line of thought, and when i carried out the volume learning procedure this time i blocked off the crankcase vent, in the intake pipe.

Now i carried out the complete accelerator pedal released, throttle valved closed learning and idle air volume learning procedure.

With out the PCV system working it was able to drop the car down to 650RPM, which is required for the ECU to acknowledge the procedure and hold it in the memory.

Now after reving it a few times to confirm it was learnt, i turned the car off, reconnected the PCV lines and restarted to car to confirm it was all learnt.

Now my car is back normal. hope you guys can get yours running ike it to.

Cheers

Pete

[andy65b]

Hey Guys,

I have managed to get the car all up and running correctly.

Idle Air Volume Learning procedure all complete.

ANDY65B - i followed on further from you PVC line of thought, and when i carried out the volume learning procedure this time i blocked off the crankcase vent, in the intake pipe.

Now i carried out the complete accelerator pedal released, throttle valved closed learning and idle air volume learning procedure.

With out the PCV system working it was able to drop the car down to 650RPM, which is required for the ECU to acknowledge the procedure and hold it in the memory.

Now after reving it a few times to confirm it was learnt, i turned the car off, reconnected the PCV lines and restarted to car to confirm it was all learnt.

Now my car is back normal. hope you guys can get yours running ike it to.

Cheers

Pete

Hi Pete

That is great news.

So I take it you have not changed you PCV yet.

Are you going to change the PCV?

From what I read the PCV should not be venting at all at idle. From what you said here I take it that the PCV is leaking and was stopping the car set the idle.

Cheers

Andy

[andy65b]

Hi Pete

Did the same procedure and idle has set and on 2 restarts in my drive way has held.

It looks like the PCV when it starts to fail stops the idle setting in the range and this stops the computer locking it in as it is outside the acceptable idle range.

It is good to see Nissan mechanics understand their own engines. LOL. I know our car are imports but they are fundamentally the same engine as the 350Z so they should know this stuff.

Cheers

Andy

[Pete82]

Hey Andy,

Thats great news, looks like the use of forums has once again showed that multiple minds are better than one.

Yes, it is no suprise to me that Nissan have no idea, because how many mechanics do you know clean the throttle bodies these days?

gone of the day of good service, if the computer says there is nothing wrong they have no idea.

Anyway, i will be looking into replacing the PCV? How much was the one you ordered?

Good work,

Cheers

Pete

[andy65b]

Hey Andy,

Thats great news, looks like the use of forums has once again showed that multiple minds are better than one.

Yes, it is no suprise to me that Nissan have no idea, because how many mechanics do you know clean the throttle bodies these days?

gone of the day of good service, if the computer says there is nothing wrong they have no idea.

Anyway, i will be looking into replacing the PCV? How much was the one you ordered?

Good work,

Cheers

Pete

I was quoted $50 from my work shop.

My car was so much nicer to drive today. Thank you also as had you not posted about your problem I would still be looking for an electrical problem.

I just enjoy learning more every day about how this car and motor's in general work.

Cheers

Andy

[Pete82]

Hello,

With the dramas i had diagnosing this problem, i found a wreckers that had a spare V35 Throttle body, so i went ahead and ordered it.

Now i have fixed the problem i have a surplus Throtte body.

If anyone needs a second hand, good condition throttle body PM me for details.

These throttle bodys are used on the V35, M35, 350Z and im sure anything that has a VQ35 in it.

Thanks

Pete

[zei20l]

how much you want for it?? if its larger than my VQ25DET one ill take it off your hands........

[iamhe77]

how much you want for it?? if its larger than my VQ25DET one ill take it off your hands........

I say go for it if it is a decent price.

Don't know if the VQ35 one is larger or smaller, but it is definitely different to our NM35 units.

Oddly, the E51 elgrande (which has less power than the VQ35 V35) uses the same as what we have, could mean it is smaller although 76mm ain't that small.

Anyway, Parts Master pics for reference of which model uses which Throttle Body (with part number).

VQ25DET powered M35

VQ35DE powered V35

Edited July 16, 2009 by iamhe77