5000+ RPM misfire, *updated 9/12*

[Joe]

keep me updated, ill update this thread as i troubleshoot more

[gawdzilla]

is the exhaust camshaft itself damaged? try to shine a light in there and see if you still have the mating surface there on the camshaft. use some qtips or something and try to clean it out some so you get a clean mating next time. i would imagine the CAS mating half is much more fragile than the cam half. it seems like its pretty easy to mess up the CAS half of the mating teeth when installing, just be gentle when pushing it in. it only goes on one way i'm sure you know that. also on your replacement CAS, use some brake cleaner and qtips. i found that the inside of mine had some random gunk in it, probably old grease or something.

just giving some advice, i'm sure you already know this. i tried a bunch of different turns with my CAS before it went in smoothly. good luck, keep us posted

[Joe]

haha yea the cam itself is fine and i know its keyed but i need a replacment now lol, its good advice for others tho

[Wulfgang]

.... all it is is a hall effect sensor. ....

Hall sensor? I thought these were optical, like the KA. If it's a hall sensor, then a little vibration or trash probably won't bother it, but if it's optical, then every little bit of dirt can cause a misread and vibration can easily cause jitter or misreads.

[Joe]

its a rotating disc with small squares cut in it.

[Joe]

can anyone confirm one from a RB20 will work?23731 08u00

thats the part number on my r33 one.

[Joe]

just used kraytons CAS to test because mine isnt here yet (thanks krayton)

car did awesome. no misfire at idle or loaded all the way to 7200.

only took it out for about 15 minutes but it looks like that was the issue.

also on a related, or what i thought was unreleated note, this problem got solved: when i used to switch my 2nd fan on i would get a sudden pause in rpm, litterally a tenth of a second only when i switched the fan on. that problem is gone also. i thought it was the way i had the fans wired but i guess i was wrong.

[240sxed]

good to hear. Glad you found the problem

[AxiOn419]

I had this same exact problem the other day. It was after I washed my engine though, so Im assuming it was an electrical issue. But it hadthe same symptoms you said right at 5000 rpms. Did the engine get wet at all by chance?

[Joe]

haha my car hasnt seen water for about 2 months

so no it didnt get wet lol

[Joe]

new cas is on and working with only 1 fatality. the alingment dowell on my camshaft. apparently the mitsubishi cam angle sensors have a hair (1mm) deeper spline than the hitachi ones. so at just the right angle the dowell fits in and SNAP when you tighten it down. none the less i just have to aling the cas manually when i remove it and it will cause no problems once the engine is running/timed.

so watch out for those swapping CAS.

[eh?]

what's the hitachi out of? FAST lists four CAS for the r33 rb25- 23731-02u19, 23731-02u11, 23731-08u00, 23731-5l300But there is only one cam and dowl pin listed.BTW: I just got 2 CAS yesterday if you still need it.

[Joe]

the htiachi was my origional one

and no i dont need it anymore, thanks tho.

[USMCgetsome]

how much you want for the cas?

[krayton]

new cas is on and working with only 1 fatality. the alingment dowell on my camshaft. apparently the mitsubishi cam angle sensors have a hair (1mm) deeper spline than the hitachi ones. so at just the right angle the dowell fits in and SNAP when you tighten it down. none the less i just have to aling the cas manually when i remove it and it will cause no problems once the engine is running/timed.

so watch out for those swapping CAS.

i just wanted to throw this in here incase someone else has this problem.

just to make sure you line the dowell inside the casing. found this cool pic from AEM forums: