rb26 ignition timing boucing when warm

[gezed]

I think a similar question has been asked before but no confirmed answer was given, but I noticed recently that when the engine is warm, and by simply taking the rpm above idle, when the engine comes back down to idle the ignition timing will bounce between 6-23* and the rev would also bounce along with it between 1400-1500rpm for a good 5-10 seconds and then idle will settle at 1050rpm

I was monitoring everything with the PowerFC Commander

previous threads I've read suggested that the CAS was the problem, can anyone confirm this?

any input would be appreciated

Thanks!

[steveo1502]

Yes, I've had same problem, was the cas

[gezed]

just a follow-up question, having a hard time finding a rb cas and looking at the vg30 units, they look pretty similar

anyone know if thats a possible solution?

[Skym]

Bouncing idle can be o2 sensor related (my car would idle bounce and was combination of idle stabilisation tables changing ignition timing, o2 sensor making ECU making engine go lean, rich, too thick oil which makes engine struggle to idle). With stock ECU and most aftermarket stock ECU's there should be base idle timing (CAS) which stays steady at 20 degrees BTDC at 950rpm and idle stabilisation varies ignition timing + or - 5 degrees or so (picked up via timing light for cylinder 1 coilpack, then ECU fires the rest of cylinders in sequence).

You can rebuild CAS. The bearings inside are why it causes hard starting when engine is cold or hot, stalling, etc and need to be replaced (NTN brand bearings and 2x different part numbers on side of bearings).

The donut part Mitsubishi doesn't make anymore (what I was told), but there is an aftermarket version (I think from Taiwan company).

I was told there is another donut part (I think Bosch brand), but requires changing plug on loom to suit. I think the pin that holds part that engages exhaust cam is tack welded in place, so need to grind off weld and use 3 prong puller to remove bearing. There's a how to on AEM forums (to fit their aftermarket timing disc).

Can buy new CAS here -

http://www.kudosmotorsports.com/catalog/nissan-cam-crank-angle-sensor-cas-genuine-nissan-skyline-r32-gtr-gtst-gts4-gts25-r33-gtr-gts25t-gts4-p-1176.html

[gezed]

hmmm maybe ill try turning off the O2 feedback on the pfc see if it helps

[BenC]

I have a couple RB26 CAS here PM me

[Dragon Humper]

I have no O2 feedback and it does this. It's definately worse after a heatsoak for about 20 min. or so after a full warm up. The timing will vary up to 30 deg. Once the motor has been running a bit it stablizes to the aforementioned +- 5 deg for idle. I have noticed this year that the CAS makes a little bit of noise dead cold, sounds like brgs are dry kind of noise. It goes away but I never noticed that before.

Time to put in my spare CAS.


Jon.