Possible vacuum leak?

**shaggsm3ls1** · 10-04-2009, 03:27 PM

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

**Cutlass** · 10-04-2009, 05:08 PM

No MAF sensor or PCM tune can do that. It could also be the VATS security system

**shaggsm3ls1** · 10-04-2009, 05:23 PM

Originally Posted by Cutlass

No MAF sensor or PCM tune can do that. It could also be the VATS security system

Are you saying that neither the MAF or a bad tune could cause that? And if so, does that mean it's more towards a vacuum leak then?

Also, whats the VATS security system, and what can I do to check/fix it?

**Cutlass** · 10-04-2009, 06:08 PM

No sorry. I meant not having a MAF or tune can cause problems.
VATs: http://www.ls1.com/forums/showthread...highlight=VATs

**shaggsm3ls1** · 10-04-2009, 06:58 PM

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

**PFM** · 10-05-2009, 07:21 AM

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.

**shaggsm3ls1** · 10-05-2009, 07:52 AM

I guess it'll be easier to diagnose once the sensors are in, but it's taking ups for ever to get here

**0rion** · 10-05-2009, 10:26 AM

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.

**tep98ws6** · 10-05-2009, 12:36 PM

need inputs for the outputs

your build is really neat though, i'm excited to see your finished build

**shaggsm3ls1** · 10-05-2009, 02:41 PM

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?

**Cutlass** · 10-05-2009, 06:50 PM

It doesn't seem like a vacuum leak problem at this point.

**tep98ws6** · 10-06-2009, 11:14 AM

Originally Posted by shaggsm3ls1

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?

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