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Rb25 Idle, Now Cas Issue? Advice Pls

hardsteppa

By hardsteppa,
in Engines & Forced Induction

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hardsteppa Grand Master

hardsteppa

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Been chasing an intermittent idle issue now for a while, and just got an ECUtalk lead and software for the laptop... Set it up in the car, found ignition timing was showing a solid 15deg at startup, but after about a minute or so running, timing started jumping around constantly between 0-10 deg on idle. Everything else was reading pretty steady apart from O2 voltage which i think is supposed to jump around between 0-1v and it was, so normal? Ignition timing held pretty steady when high in the revs apart from the occasional blip of a couple of degrees either way, but back to jumping all over the place between 0-10 as soon as the throttle is let off and back to idle.

So is this pretty conclusive then, that the CAS is rooted? Or could it be just indicating something else to be checked, before I go spend a fair chunk of cash on a new CAS?

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89CAL Grand Master

89CAL

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Standard ECU I'm guessing?

Reset the ECU and let it idle/take it for a drive and see if that changes anything

Also does the CAS sound/feel wrecked? Mine was making a slight grinding noise when it died, I pulled it off and could barely turn the shaft. Went one step further and pulled it apart, found that the bearing at the very front of the unit was dry as

timing should not be 0 at idle or even 10. 15-20 degrees is about right

hardsteppa Grand Master

hardsteppa

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yep, standard ecu. It's been reset many times since this first started happening, hasn't helped.

Pulled cas off this morning, felt ok, maybe slight roughness of bearing but not much. Can hear a bit of rumbling sound from that area while the car is idling though.

LOl i know 0-10 is not right :P that's why I mentioned it. Timing is set to 15deg though, and showed as this when first started yesterday, sits on that when the car is running right too...it's just the issue is getting more and more frequent. Also noted when out driving yesterday, when coming down in revs back to idle, it occasionally locks on a steady 20deg which makes it idle at around 1200rpm. A blip on the throttle brings this back down to a more normal idle, although with erratic 0-10deg timing.

hardsteppa Grand Master

hardsteppa

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i should also point out, timing is erratic only with TPS connected. When unplugged it idles at a steady 15deg, but jumps around once plugged in, TPS voltage readings are fine though and steady, not jumping about. Have tried another CAS and same result.

  • 4 years later...
GTSBoy Grand Master

GTSBoy

Posted
Posted

My experience is that the timing will do exactly as described when the idle screw is set too high.  The ECU tries to control idle speed with reduced timing.  The first test is to wind in the idle screw and see if the timing starts to come back.  In my car, after a number of other issues were dealt with, I had to wind the idle in about 5 turns before the ECU gave up trying to pull the timing back to 0-5°.

hardsteppa Grand Master

hardsteppa

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Yes, was afm needed cleaning. As far as ignition timing goes, gtsboy is correct again lol. Timing is supposed to be erratic but having idle set right without idle control on, makes it less so.

Mirroz Newbie

Mirroz

Posted
Posted

allright thank you i will try to set my idle lower, but its 850 right now and ecu screw is in factory position. and iw cleaned afm and the volts seems to be right checked it with consult 1.14 at idle and i think they went around 4 when pulling hard at second.

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