Need help for rb25det....

[owtaman]

I have a RB25DET, yes it does behave erratically at 650rpm when the aircon is off, try to pump RON97 it will reduce the symptom a little.

 

[owtaman]

Hi Guys,
Does anyone else having this problem with RB25DET ? Just want to see if this is a 'known issue' that is perceive as normal or it does indicate a problem.

Engine does not stall, at idle, occasionally the idling speed would slowly drop below the 650RPM(standard idle speed), then it would automatically attempt to raise the idling but will then immediately drop below the standard 650RPM again, making the car vibrate more than usually would expected, leave it to behave like this for awhile and it will stabilize it self but after a few minutes the symptom comes again... feels like the ECU is trying to run lean at idle speed to save petrol but it does not able to do so properly, give it a quick step on the throttle it will be fine but will resume the symptom again.

 

[a31gtst]

Its called hunting.
Your ecu is not getting a signal from one of the sensor's and is trying to search for it, thats why you notice the idle going up and down.

Check your AFM, O2 sensor and the AAC valve. Do a search and you should get all the answers you need. If you have a good mechanic who is familiar with RB's than just get him to swap out the mentioned sensors above with spare ones one at a time to eliminate which is the faulty one. If its not any of the above you could have some wiring issue.

 

[Dr.D]

do diagnostic on ur ecu n check if any sensors not performing up to par..

 

[owtaman]

Thanks for all the inputs, I plan to bring the car to Ah Man in USJ industrial area to run a diagnostic, heard that he is the wiring king in Subang area, anyone use his service before ? Care to share ?

 

[owtaman]

I edited this box so as not to confuse other forumers of what I did to fixed my idling issue, I finally concluded that the solution for it is to service both the idling valve (AAC) and the throttle body altogether.

 

[owtaman]

I did a Dyno recently and while trying to get a good leaner AF ratio at the idling RPM range for fuel saving purpose([email protected]), the idling become bad again, after few attempt on adjusting the screw at the throttle body, the tuner decided to tune the fuel map instead, now the RB25DEt can idle very well. GOOD !

I see this as one of the most effective way to address the idling issue for RB engines as the AAC valves you will find at the chop shop will not be likely to be in good condition due to age and dont think you would want to source for a new one too due to price, but most of the time you will have some kind of after market ECU installed in your car.

 

[kaminari]

Idling on RB engine doesn`t only rely on AAC valve. Irritated voltage on AFM sensor will also make your idling unstable. Your tuner not only tuning the fuel map but also adjusting idling voltage which feature in aftermarket ECU to stabilize the idling and prevent engine stall.

 

[owtaman]

Thanks for the comment above, this is good to know !
I am using the Blue color e-Manage, does this one have the features you mentioned above ?

 

[bnr_32]

emanage blue sure have 'anti engine stall' function like what kaminari mention earlier :top:

 

[owtaman]

I just did a full tank of RON95(since RON97 is now RM2.90), ran it for two days, on the first day the idling issue seems getting a bit more obvious but it was fine on the 2nd day after a long drive back.

But I notice if I let the engine idle without the key(turbo timer on), the idling seems more erratic(on both RON95/97), is the turbo timer not supplying enough voltage to the ignition wiring/engine ?

 

[owtaman]

Recently brought my car to a workshop who is familiar with Nissan FR car to fix something, the mechanic Ah Siong listen to my engine and said,

'This is not RB sound, got brrb brrb brrb from your exhaust, atleast one cylinder is not firing properly so there is only 5 sparks running, so this is not RB sound..' (ok I get it RB has 6 sparks)

Went and bought 2 used ignition coils, replaced them on no.2 and no.4 since they look more 'wet' in there due to fuel not burned well.. and WOLLA !!! Idling is now 95% stable !!! :D

The idling RPM still occasionally experience slight drop and regain, but it is now not anywhere near to stall.. Good !

Brought the car back to JC Racing to fine tune a bit on the idling fuel setting, now idling is even more stable(97% nice) and response better from idling up, Good !

Maybe I should replace all spark plugs($) and get Splitfire coils($$) to fully ALL SPARKS my RB25DET.. hmm.. okay, a little Bumble Bee is acceptable for now.. :)

 

[V-Spec]

With 5 cylinders running, it sure does sound like a boxer right?

 

[owtaman]

No wonder I was saying to my friends that RB exhaust note sounds like a boxer.. so its actually a 5 cylinder RB that sounds like a boxer !

On another note, why do I feel that GTR35 VR38DETT sounds similar to RB engines, I mean.. yes people still associate GTR35 with Skylines although on paper they are not, but this is a V6 instead of a I6 layout, what is making them having this similarity ? What is common in these two engines ? Or is it just me ? Any body feel the same ?

 

[[PIMPIN]]

What is common in these two engines ? Or is it just me ? Any body feel the same ?

They both have 6 cylinders and both are made by Nissan?