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Old 08-14-2011   #1
Penitent_Spark
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Default RB25 Unsteady Idle

Hi All.

I have recently purchased a R33 Series one. What I have noticed at first was that would idle hunt when warm, so much so that if left unchecked would stall. So over a matter of two weeks I cleaned the AAC valve and found a vacuum leak. The Oil Breather hose was split on the right side, so i replaced the oil breather hose with a second hand one, and replaced most of the vacuum hoses on the car. No the idle doesn't hunt as much, it only hunts by 50 - 100 rpm at idle. I am not sure if this is normal, or is it just the RBs can not idle that steady?

Also there is a ticking sound at the back of the engine, near the power transistor pack and AAC valve area, it is not a rhythmic tick, but comes on and off occasionally, usually followed by one tick, then quickly by a double tick. Is this just the AAC valve doing it's job, or is something else going on that I am not privy to?

Thank You
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Old 08-18-2011   #2
bobbo
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Default Re: RB25 Unsteady Idle

You may still have a vacuum leak somewhere. Unfortunately I have no experience with the R33 or the RB25. My experience with with the R32 RB26.
50-100rpm isn't bad. Is it still just hunting only when warm?
The ticking shouldn't be the AACV although it is possible as it does cycle open/close.
It could possibly be a lifter getting tired. What oil/grade are you using? How is your oil pressure at idle?
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Old 08-18-2011   #3
geoffree
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Default Re: RB25 Unsteady Idle

25 will idle as sweet as.
You don't say what your idle speed is.
If it's way up 1500+ from a big vacuum leak, they'll hunt due to the overrun fuel cut V's TPS position.
As you're in Aus, why not post this on SAU, you may have a fellow owner living around the block who can drop over for a look.
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Old 08-18-2011   #4
Penitent_Spark
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Default Re: RB25 Unsteady Idle

Thank you for the replies.

My Idle speed is around 720 - 850rpm, this is what it's hunting around only when warm. I have posted this in SAU with not many usefull replies. The hunting, as mentioned, was much worse before. This weekend I will check the TPS voltage and setting, and see if that's set correctly.

I will keep looking to find the symptoms. I am slowly remedying the problem, at least it doesn't stall anymore.
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Old 10-03-2011   #5
kjls
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Default Re: RB25 Unsteady Idle

I had a similar problem a few years ago, turned out to be the factory BOV was leaking. Might be worth checking.
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Old 06-23-2015   #6
Penitent_Spark
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Default Re: RB25 Unsteady Idle

After 4 years I have come back to this post to close of lose ends. About a year later after this post I solved the problem.

->The igniter packs were old and produced considerably weak sparks.

This was of course after:

->All air and auxiliary hoses were replaced
->The Air Flow Meter Was replaced
->The auxiliary breather was rebuilt
->The engine head was rebuilt, pressure tested and skimmed (1/1000) (not in attempt to solve this problem, this is another story)

Unfortunately, out of this experience I haven't come away with a reliable method of diagnosing and solving idle hunting. Other than leave nothing out of scrutiny once an engine is idle hunting.

Now of course, the RB25 sits steady on 850 RPM, when warm.
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