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BOV problem.... effecting idle?


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I just completed a turbo build on a stock KA24E. I had a heck of a time starting it up...wouldnt hold idle..... and tracked the problem down to the RB20/DSM style BOV.


The BOV is vented to atmosphere and I discovered that if I cover up the vent/opening my RPMs go up and idles fine. In fact I can then reduce idle and it purrs.


Im assuming the BOV is stuck open and drawing air. Is there anything I can due to the BOV to make it seal or is it trash and I just need to source a new "used" one?


All comments appreciated....its an econo/cheapo build and Im doing my best to keep it that way! :D


On that note.......Anyone have a spare kicking around ..if so please give me a shout.



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Are you using an aftermarket engine management system? If not, is the stock ECU MAP-based?


If the stock system is not MAP based, an atmospheric BOV that opens at idle can cause problems. It is essentially a large vacuum leak.

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Stock ECU....No worries I understand. Its a lapping car that will be running full out when on the track...Im not concerned. I run my RB20DET the same way. Mind you with a Power FC and MAF...not MAP. It runs like a dream on the street.


As far as the RB BOV....I did crush the top and it did tighten the spring but that didnt help. I was about to give it one more whack when I thought Id try to blow into the vacuum nipple to see what would happen. I heard an air hiss, so I flipped it around to see where it was comming from and found a small hole..... 1/16" or less.....right beside the large one. Obviously the RB BOV is not designed to run atmospheric and has the small hole for balance or something?? Bottom line its a non stop leak when connected to run open.


I put a small piece of electrical tape over this hole, bolted it up and started up the car...it idles perfectly. I will TIG weld this hole shut and start working on the next problem.


FYI...I removed every single emission device from the KA....attached a Z31 turbo on a log manifold.... hot piped it to the intake ...with a stock ECU......and so far the only issue(s) was a dead battery and this BOV deal. And they said it couldnt be done....mind you it hasnt run under load yet. :D


Thanx for your replies!


Are you using an aftermarket engine management system? If not, is the stock ECU MAP-based?


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