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VPC Help, Bogging down and jerking

BoostedAWD91

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Mar 1, 2007
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Danville,Pa
i am running a VPC with keydiver chip. I was having problems with the car bogging down and jerking alittle under boost which i figured the map sensor was going. So i just replaced it with a GM 3 bar map and it made it worse. i can barely even make it up a steep hill now. It is wired up correctly, would the settings on the VPC/GCC cause this if they were way out of tune? It worked fine before exactly as it is now, then just started to bogg and jerk under boost so thats why i replaced the MAP. what else could be causing this?
 

turbowop

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Apr 29, 2001
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11,971
Location
Yakima, WA
Boost leak? I realize speed density is less sensitive to boost leaks compared to a MAF system, but maybe? /ubbthreads/images/graemlins/dunno.gif If it just started happening out of the blue, I would suspect something other than the tune.
 

BoostedAWD91

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no not a boost leak. It just started doing it one day, it was minimal and slowly got alittle worse but it was still driveable, up to 7 psi it would bogg and jerk and once i hit 10psi+ it worked fine. I figured the MAP sensor was going bad so i replaced the HKS map with the GM 3 bar map and now its very very bad.
 

BoostedAWD91

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i was trying to get this fixed 2nite so i can take the car to the East Coast shootout but its not looking promising /ubbthreads/images/graemlins/banghead.gif
 

NateCrisman

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Nov 22, 2008
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2,054
Location
Blairstown, NJ
Are you sure there isn't some other issue?

plugs been replaced or gapped recently? wires not cut or arching?
fuel filter plugged or fuel pump losing pressure (oring leaking on the pump, or pump dying)
 

BoostedAWD91

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no i just replaced the spark plugs today, no vaccuum leaks, fuel filter is new, fuel pressure is good. im wondering if maybe the vaccuum line going to the map sensor is pinched off somewhere, but its only under heavy load and boost
 

BoostedAWD91

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Mar 1, 2007
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Danville,Pa
Quoting keydiver:
Do you have a logger to see what the Hz output of the VPC is doing?



i replaced the vaccumm hose today and made sure that was fine and no changes.
the logger results
RPM 3406rpms
INJP 4.86MS
o2 0.01V
TPS 75.7%
INJD 13.2%
TIMA 28 degrees
MAFS 257.8Hz

RPM 2812rpms
INJP 3.83ms
O2 .74V
TPS 32.4%
TIMA 31 degrees
MAFS 157.2hz

Im sure sure exactly what the HZ's are supposed to be but its hard to even get it at WOT cause as soon as u start to put alittle foot into it and start building boost, it just bogs down hard
 

I don't think anyone can tell you what the Hz should be a certain boost level, the important thing is that it is changing. What Hz is it at idle? 30-40?
 

BoostedAWD91

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Danville,Pa
ok i didnt know, ill have to check the log tonight when i get home to see what it was at idle.

Are GM Maps ok to use with the VPC? i dont know what would be causing this. ill put the original map sensor back on and see if it gets better. At least with that original map i was able to drive the car, with the GM map the car is pretty much worthless, but im dont know if thats actually the problem or not.
Jeff, when u burn ur chips for the VPC, would changing to a GM Map throw anything off?
 

If you are sure that you have the GM 3 BAR MAP sensor, there shouldn't be any difference between that and your stock HKS sensor. If you were to use a 2 BAR, it would give the VPC wrong information, that there is much more boost, so you would be VERY rich.
 

BoostedAWD91

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Danville,Pa
yeah its actually Hill's map he just bought that i borrowed to try. It isnt a actual GM map, its another company so i cant check the 3 digit # on it to confirm it but according to RockAuto's part # it is a 3 bar.

i just dont understand why the original Map works fine 10psi and + and the car is driveable but with the GM map the car is pretty much worthless trying to drive.
 

BoostedAWD91

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Danville,Pa
yeah i just mean the actual GM ones have the GM logo stampted on them with a 3 digit code which tell u if its a 1,2 or 3 bar and that doesnt have any numbers on it.
 

1941Galant

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Aug 21, 2004
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1,909
Location
Charles Town, WV
Isn't the number 12223861 stamped on the map sensor? If so, that is the # for the GM 3 bar map sensor. If you don't believe me it is on the DS-Map forum, and you can even see the # in all 3 of the links that keydiver posted in your other thread.
 
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