Jump to content
SAU Community

Recommended Posts

Before anyone asks, yes i've done the usual searches but I couldnt find anything definitive :10_wink:
 

Background: Stock Rb25det NEO. standard intake, exhaust, boost and ecu.
Engine shuddering or hitting fuel cut whenever WOT and high boost (bucking like a mechanical bull), other than that, it ran fine. boosted down low ok, seems to run smooth(ish). didnt run rich, was getting on average about 450k's per tank
Replaced spark plugs with NGK coppers (1.1mm). Car then had absolutely no torque down low, would backfire constantly when cold or after WOT (which was necessary to get the friggin thing to move) and wouldn't rev over 5000rpm. It felt like it hit Rich and Retard. No codes were thrown

I noticed that the boost gauge was reading a little high after the plug change, and found a vacuum line from the charcoal canister had frayed and cracked causing a vacuum leak. Replaced this and boost reading went back to normal.

I then replaced the Airflow sensor (2nd hand from wreckers), Coilpacks (splitfires), Coilpack lead (Genuine) and Sparkplugs (NGK BKR6EIX-11).
This made a HUGE difference. the old coilpacks were likely from the factory and were just producing a weak spark.
Reset the ECU, still ran rich when cold (but not as rich), low-down torque came back but still cant rev over 5000rpm (feels like the engine just goes back to the R&R state)
It does backfire a little when cold or after WOT (more like a few pops instead of a full blown backfire). Still no codes thrown

Does the ECU lock out the top 2000 RPM when its 'learning'? or is it something else?

What should I be looking at next?
O2 Sensor?
Replace/check all Vacuum and Intake lines?
Cam angle sensor?

Really running out of ideas here

Link to comment
https://www.sau.com.au/forums/topic/473845-rb25det-neo-not-revving-past-5k/
Share on other sites

  • 3 months later...

So this saga is still going on.
Taken it to two separate mechanics, both said that it 'seems' fine.. (despite the fact it cant even get close to the rev limiter in 2nd) 

Ran a boost leak test using my puny ryobi tyre inflator, it held 5psi for about 20 seconds which appears to be ok.. it seems that there's something else going on.
I've plugged in the consult cable and engine temps appear normal as far as i can tell.

Also appears that i'm running .75 bar of boost now (up from .5).
I changed the vac lines to and from the turbo and solenoid hoping that it was just a leaking line that was throwing everything off, still no joy (hiss/whistle noise cant be located with soap and water on any of the couplers)

I'm starting to think now, no power past a certain rev range + hiss/whistle noise + higher boost..  could it be an exhaust leak? or am i just reading too much into this?

Edited by lench
  • 7 months later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Time to decide what’s more import, your power level or your budget because you’re going to struggle to keep both 
    • Our Southern Highlands Cruise is proudly registered with “R U OK?” Day.  Sometimes the best way to check in on your mates is by getting out for a drive together. Sharing a common passion like cars creates the perfect space to chat, connect, and support each other.  A simple “R U OK?” can make all the difference. Let's enjoy the drive, the company, and look out for one another. PLEASE WEAR YELLOW FOR “R U OK?” DAY Sunday 14th September 2025 9:30AM Meeting Crossroads Homemaker Centre 10:00AM Cruise Departure Via Old Hume Hwy 11:45AM Arrival at Mittagong RSL Club Meet Location: Crossroads Homemaker Centre Final Destination: Mittagong RSL Club *Disclaimer* There will be a lead and follow car so no one should get lost. If you would like to attend or bring others along please put your name down and a +1 as numbers will be needed prior! This is NOT a race and we will all be adhering to all road rules. If this is what you want please come to one of our many track days. This is an official SAU:NSW event and will be run under a CAMS permit. One of the things that really sets our club apart is our commitment to being true enthusiasts. When on normal roads we strive to maintain good relations with the authorities as well as the public in general. When attending one of Skylines Australia NSW events please try to: • Be aware of surrounding environment and act accordingly. • Drive courteously on the state’s roads as a true enthusiast should. • Understand how important it is to maintain the good name of SAU NSW and thus, treat others accordingly. • Any misbehavior will not be tolerated and you will be asked to leave.
    • Yep, its been down for a while, as I understand it it will be back soon.
    • Yeah I also looked at Plazmaman, but, it ended up alot  cheaper getting black ones through EFI when you also added in the delivery cost
    • Nice shot! They look super clean. The roof rack delete on the black one is interesting. Would like to see more pictures from different angles. It's subtle but could make quite a difference to how the car looks in profile.
×
×
  • Create New...