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Thread: Possible vacuum leak?
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10-04-2009, 03:27 PM #1
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Cosmos black- 1995 BMW M3
Possible vacuum leak?
I just test fired my LS1 swap in my BMW last night. It fired right up but then died almost immediately. I installed a MS3 cam and Patriot heads with upgraded pushrods before I dropped it in.
I am missing a few sensors like the coolant temp (to the dash), air charge sensor, and o2 sensors. I plugged the EGR, charcoal vent solenoid, and brake booster because I don't need them.
My question is, will the car run without any of the above mentioned sensors, and if so, does my problem sound like a vacuum leak? I don't know if it's because of a leak, missing sensors, no PCM tune, or a combo of the three.
Any help will be greatly appreciated. Thanks in advance guys
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10-04-2009, 05:08 PM #2
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1999 Formula WS6 M6-sold- 2001 Silverado Z71
No MAF sensor or PCM tune can do that. It could also be the VATS security system
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10-04-2009, 05:23 PM #3
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Cosmos black- 1995 BMW M3
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10-04-2009, 06:08 PM #4
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1999 Formula WS6 M6-sold- 2001 Silverado Z71
No sorry. I meant not having a MAF or tune can cause problems.
VATs: http://www.ls1.com/forums/showthread...highlight=VATs
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10-04-2009, 06:58 PM #5
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Cosmos black- 1995 BMW M3
Oh ok. I just tried to fire it again, but this time when it started the revs jumped to like 1.5-2k so fast that I got scarred and shut it down right away (MS3 cam, LS6 heads, and open headers = I bout shit myself)
I thought it was a fluke so I did it again, and again the revs shot straight to 1.5-2k so again I shut it down. My neighbor then proceeded to yell at me lol. Is it normal for a cold engine with this big of a cam to start and rev so high like that? I couldn't let it run long enough to see if the revs would come down out of fear that something might be wrong, and also the cops would have been here
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10-05-2009, 07:21 AM #6
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NBM- 1998Z28
I know for a fact that if your Water temp sensor is messed up it will definately cause you all kinda A/F ratio problems. My last bad one made the cpu think it was about -30 degrees below and it got so bad it didn't even want to start until I replaced it.
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10-05-2009, 07:52 AM #7
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Cosmos black- 1995 BMW M3
I guess it'll be easier to diagnose once the sensors are in, but it's taking ups for ever to get here
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10-05-2009, 10:26 AM #8
you will definitely need the coolant temp and IAT sensors. I suspect that car won't run very well at all with that cam and no tune. With the revs shooting up like that I suspect something is going on somewhere with the airflow or throttle body. Get the sensors in there and button everything down before going any further. No sense in trouble shooting a motor that's not complete....just a guessing game.
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10-05-2009, 12:36 PM #9
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Arctic White & Black- '98 WS6 M6 - SWAPTIME!
need inputs for the outputs
your build is really neat though, i'm excited to see your finished build
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10-05-2009, 02:41 PM #10
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Cosmos black- 1995 BMW M3
Well I found out that the VATS is still enabled, so that's definitely part of it, but yeah, I'm just going to get it all together, tow it to a shop, and have them use HP Tuners to disable VATS and get it running smooth.
By the way, if it is a vacuum leak, how do you check? Just listen for air, or use some sort vapor dye?
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10-05-2009, 06:50 PM #11
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1999 Formula WS6 M6-sold- 2001 Silverado Z71
It doesn't seem like a vacuum leak problem at this point.
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10-06-2009, 11:14 AM #12
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Arctic White & Black- '98 WS6 M6 - SWAPTIME!
Like Cutlass said, probs not a vacuum leak, but to test a vacuum leak - rig up a smoke machine and just watch for the leaks
http://chemistry.about.com/od/howthi...kemachines.htm
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