VMP Boost-a-Pump causing car to stall in neutral while coasting

Uncle Rusty

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Hey guys, I was just wondering if anyone else running a BAP has ran into similar issues in the past. Recently I picked up a VMP BAP with the included PnP wiring harness for my Stage 2 VMP TVS.

However, since installing the BAP I've ran into numerous issues with the car stalling while going into neutral at highway speeds. It's especially prevalent when the car has only been running 15-30 minutes, but basically what happens is while cruising on the highway at say 60-80, any time I drop into neutral and coast there's a good change it will drop down to around 400rpm's and simply stall instead of staying at the normal ~800. Looking at my Aeroforce, voltage is running at around 13.4-14.0 volts depending while the car is running.

I currently have the idle set to 850RPMs on the SCT, and for the install I simply used the included PnP harness and the nearby ground located in the trunk. I've watched it stall several times, and have noticed that if I catch the RPM starting to dip, that if I tap the throttle it won't stall and will idle normally. When the car dies voltage drops back to around 12.1 since the alternator isn't running any more. I never have any issues with getting it to start right back up however.

I've been talking to Justin abou the issue, but was wondering if anyone else has ever ran into similar issues or has any ideas what might cause this? To me it almost seems like the BAP is demanding too much power from the alternator when the engine shifts from running at a higher to a lower RPM.
 

Zona14Stang

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Hmm that is weird. I have the BAP too. Why are you going into neutral at highway speeds? Just curious.
 

Uncle Rusty

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Usually just to coast on country roads say if a stop sign or light is coming up. Or in some cases after I pull hard and get up to speed (Well above in some cases), I'll coast in neutral for a bit until I drop back down to 60 or 70 and then shift into 6th. I guess I should say country roads more so than on an actual highway, no reason really to normally do that unless stop and go traffic comes up...
 

benzopyrene

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This happens to me too veryoccasionally after installing VMP SC and tune. I just assumed it was just a tune tweak.I dont hae a BAP....My money is that a slight tune adjustment would fix this problem for us both. Cheers!
 

Uncle Rusty

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Hmm interesting, well I'll see what else Justin has to say then if it could be the tune. I'm going to be installing ID1000's soon so I'll be getting a revised tune for those anyway.
 

mhyjek

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"To me it almost seems like the BAP is demanding too much power from the alternator when the engine shifts from running at a higher to a lower RPM." So this a continuous setup not boost referenced. I have vortech programmable boost referenced one it work flawless plus it is only bumps voltage when seeing boost so you don't tax the fuel pump. I heard great things about VMP but wonder why they wouldn't have that option
 

Uncle Rusty

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Yeah, I'm not sure why they don't have it as an option either. I have heard that it's more difficult to tune that way, and you also have to worry about the voltage always increasing at WOT to make sure it doesn't lean out.
 

mhyjek

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Haven't seen that in logs car keeps afr 11.3-5 pretty tight. Also if it increased would cause rich not lean correct?
 

Zona14Stang

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I believe the factory alternator is 130A Maybe the addition of the fans, pump, and BAP is just on the line for current draw and the computer senses it. You wouldn't think so since there is no load. Possible grounding issue? I am thinking of going to e85 and getting ID1000's too.
 

Uncle Rusty

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I just got the ID1000's in last night, and Justin wrote me a new tune for them as well as an e85 tune. He said the tune was also adjusted to help with the stalling issue, and at least so far on this new 93 Tune I haven't had any issues with it stalling yet. So it seems it may have been the tune then, but we'll see over the next few days if I run into any more issues.
 

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