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Discussion Starter #1
I was digging through the service manual and I can't find anywhere that shows what the idle vacuum should be on a healthy I-4 chargecooled motor.

any of you with aftermarket vacuum/boost gauges know?

I measured mine and I it's only pulling 10" Hg. That seems really low to me. I have looked/listened for any vacuum leaks but I can't find any. I even checked the other vacuum rail that only feeds the MAP sensor; same 10". I also checked the vacuum at a steady 2500 rpm and the vacuum doesn't deviate, which is a good thing.
 

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Most cars are somewhere right around 18 in/hg, 10 does seem a bit low. Might be a good time to check for vacuum leaks, mine had a bunch.
 

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Upon messing with an ignition problem a while back I found approx. that same reading, I think its normal, about 10 in on the vacuum gauge. I at first panicked and thought that was low, then did a search and found somewhere that its about normal. The vacuum off your pump to run the brake booster and accessories is higher, I think its either 13 or 18 in at idle, I dont remember for sure.
 

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Discussion Starter #5
Thanks for the replies. I figured these engines must not have alot of vacuum if they need a vacuum pump for the brakes.

I've never had an individual throttle body engine before. Is that a function of an individual throttle body design?
 

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Mine idles at 10in at 1000 rpm, according to my VDO vac/boost gauge.
 
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