Rb25Det Boost Jumping

[wounderz]

hello i have a few problems with my Nissan skyline r34 gtt. when its under boost around 4600 rpm to 6000 rpm it is jumping around and kicks in and out. now i just check the spark plugs and they look stuff when they only not even 500ks old. has been tracked once and that's all. i just wondering if i could get some help out here.

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[Ben C34]

So you have a misfire at the most common room range ever discussed on this site?

Search and find your answer....

Or should we all guess randomly why your car is missing?

Seriously, search first. If for some crazy reason you can't find the information ask the question then.

And if you do need more help, specify what mods your car has. That will save people making wild guesses about the situation,and will show you are willing to take the time to help the people that are trying to help you.

I'll add a wild guess in, for fun. You are running more than 10 psi on stock ecu.

[Ben C34]

So you have a misfire at the most common rpm range ever discussed on this site?

Search and find your answer....

Or should we all guess randomly why your car is missing?

Seriously, search first. If for some crazy reason you can't find the information ask the question then.

And if you do need more help, specify what mods your car has. That will save people making wild guesses about the situation,and will show you are willing to take the time to help the people that are trying to help you.

I'll add a wild guess in, for fun. You are running more than 10 psi on stock ecu.

Edited April 28, 2014 by superben

[wounderz]

sorry mate but a had look!.

new on this alright. and no i am not running 10psi. its running stock .also stock ecu

next thing the plugs gone.

it doesn't back firer it just stopping boost and jumping

[Ben C34]

So your car is 100 percent stock?

It really sounds like when boost is too high on stock ecu.

It could be coil packs as they crap out around this age of the car.

Do the usual things, clean and inspect cool packs, reduce plug gap to .7 mm, clean afm.

Do you have a boost gauge? I would check your waste gate lines are in good shape and not split which would cause higher boost.

[wounderz]

so your thinking its boost oscillation.

yes it does have a boost gauge but it is off never on. well the spark plugs are really dark and having rust all over it as well. thanks mate

ya i have a look today then.

the car has only done 88000ks. plus it sit for over 3 years. but when the car has been running for a long time it does clear up a little

[Ben C34]

No, I don't think it's boost oscillation.

And whatever you think boost oscillation is it isn't your problem.

Wtf do you think that is?

[wounderz]

i think it might be turbo. that's making it jump.

when it hits 5000 plus it boost cuts in and out.

but your thinking the coil??

[Josh080691]

My guess is coil packs

[Ben C34]

As I wrote I'm also thinking you are actually running higher boost than you think.

Turbos don't stuff up and make boost jump. Something else is the problem.

Also , check for leaks in the pipework,loose clamps etc. The only way to be completely sure of no boost leaks is to pressure test,so I suggest you Google how to pressure test intercooler pipe work. A boost leak would make it run way too rich and would cause the ecu to cut as you have described.

[533 RYC]

If it was coil packs, it would certainly pull the engine light & code 21 (primary ignition signal). Engine light will also stay on till code is actually cleared.

Is the engine light on?

Question 1: Does the problem mainly occur in second gear when going for wide open throttle?

Question 2: Does it boost ok at 4psi (stock boost level) BELOW 4,000rpm?

[wounderz]

gavin when its below 4000 rpm its fine.

i think ben maybe right the is something making more boost or a leak.

but a month ago when i taken it for a drive the boost garage was hitting over 1k..

[niZmO_Man]

but a month ago when i taken it for a drive the boost garage was hitting over 1k..

That makes no sense lol.

Try replacing your spark plugs with BCPR6ES (these are 0.8mm gapped, don't get the -11).

[wounderz]

wtf the dam computer posted my comment when i wasn't finished.

what it was meant to say the boost garage was hitting over 1kg/cm on the stock garage then my boost garage was geting over 1.27kg/cm i am not sure if it meant to go that high ???? .

oh k well for plugs i have (PFR6G-11)

[Ben C34]

Are you serious........

[Ben C34]

Google what that is in psi.......

Now you can see why trying to diagnose and help people over the net is a frustrating thing.

And the record shows my first guess to be correct..... what an achievement

Edited April 28, 2014 by superben

[wounderz]

what now ben ???

mate i am just new into this gtt area!!!

i have been doing a bit of research was faster just to make a post

[Ben C34]

I understand you are new to turbo cars, but you're not new to life! Finding information in this day and age is so easy.

[wounderz]

i knew that mate.

so whats the problem since you know what it would be

[Ben C34]

Read my first post.

I can't believe I have to spell it out.

You are running to much boost.

Stock ecu has a spaz over 12psi.

You are running over 14 psi, yet in your first reply said stock boost when I guessed that you were running over 10 psi.