VPC Help, Bogging down and jerking

[BoostedAWD91]

well i put the regular MAP sensor back in today that comes with the VPC and it made it alot better than with the GM map which i dont understand. It still is bogging down and not doing much till after 10psi. So im guessing it has to be something with the MAP sensor or the VPC control unit. /ubbthreads/images/graemlins/dunno.gif

 

[Nate]

Maybe the MAP sensor that you found isn't a 3bar, or isn't up to snuff in its performance.

The issue is probably not with the MAP sensor, I've swapped them tons of times, and it rarely makes a difference.

Do the rest of the sensors test out within spec?

 

[NateCrisman]

Have you checked on a logger that coolant temp, air temp, rpm, boro pressure, signals are all reasonable. Maybe one of tue resistors in the vpc harness that lock the temp signals is popped?

 

[BoostedAWD91]

The GM Map was a 3 bar that was brand new that Hill purchased which i borrowed off him to try out
The only thing i know for sure that is alittle loose is the CTS connection in the VPC harness cause if u bump it or move it, i loose the signal, but i got it to where its been working for awhile. i know some guys dont like using the VPC to ECU harness due to these types of issues. The head unit could be bad, ive been trying to find another one to swap in to see if it makes any difference

here is what the logger is showing after putting the regular map back in.
rpm 4437rpms
injp 12.03ms
knock 0
o2 .72v
tps 99.6%
injd 44.5%
TIMA 13 degrees
MAFS 540.9Hz
COOL 182.7
AIRT 66.3 degree F (temp doesnt ever change)
BARO 13.46psi
VSS 129
MAP 25.8psi
ANA 1 235
ANA 2 165
FTRL 110.9%
FTRM 85.9%
FTRH 125%
GREV 2.02
FTO2 100%

i am still running rich even with the VPC turned back pretty far to lean it out

 

[toybreaker]

Quote:
The only thing i know for sure that is alittle loose is the CTS connection in the VPC harness cause if u bump it or move it, i loose the signal, but i got it to where its been working for awhile.



Chris,

The ecu will change timing and mix strength relative to the coolant temp. If the coolant temp signal to the ecu is moving around under boost, it can do exactly what you've got going on.

It's frustrating to troubleshoot, as it can only be occuring when the harness moves around under acceleration, and the logger doesn't always catch it.

Did you install the ect pigtail I sent you back in January?

If the connection is intermitent in the adapter harness, you might be able to bend the female pin in the connector to give better continuity.

The ecu needs a stable ect input!

 

[BoostedAWD91]

John i did put the pigtail in u sent it. The VPC harness did have a loose connection for the Coolant temp sensor but i believe i have it fixed. Before the coolant temp signal would cut in and out, but i tried fixing it and i havent had any signal loss since then so i really dont think thats whats going on.
I just took Hill for a ride and its not really cutting out or bogging down anymore. It really does seem like its some mechanical problem or something else. I am not getting any knock at 20psi, its not retarding timing much, there just isnt any power there. At 20psi with the setup i have it should be pulling alot harder than it is.It feels like a 10psi pull on a 14b right now

 

[BoostedAWD91]

im gonna do some compression and leakdown tests this weekend and see if i can find anything. I am burning coolant, not really bad, but enough to notice it when i drive car alot which i havent done for awhile since i bought a DD. hopefully i didnt block the headgasket

 

[atc250r]

Get rid of that stupid harness that HKS used and have keydiver burn you a chip that locks the values inside the chip so that you don't need the harness anymore.

 

[BoostedAWD91]

Jeff did burn the chip specifically for the VPC but not sure if he had everything in there to where i dont need the harness. I would still have to wire the head unit into the ECU though correct?

 

[atc250r]

Yeah, you hard wire (SOLDER) the VPC wires into the ECU. It pretty much the same wires as an SAFC would get IIRC.

John

 

[BoostedAWD91]

ok ill look into doing that. i know there is a discussion about how to do this and what goes where somewhere on the board

 

[atc250r]

Yeah, I'm sure there is. If you can't find it I'll try to look through my notes/files and find which wire goes to where. Are you on the Yahoo VPC group? There is a bunch of good info on there.

John

 

[Nate]

Sorry if I'm repeating a question that was already posted, but have you pressed-checked the IC system? I only ask because I ran into this stumble the other night, and it turned out to be a massive boost leak. Once the leak was fixed, the car was fine.

 

[BoostedAWD91]

John no im not on the VPC yahoo, i didnt know there was one. Ill look into that as well.

Nate, i have pressured checked and i dont have any leaks except for a real little leak at where the IAT is at which no matter what i try i cant get rid of. It is only doing it at low boost, once i get up around 10psi and above it pulls fine without bogging or anything. The only thing is that it just has no power there anymore. At 20psi on the t3 57 trim setup i bought of zach it feels like a 10psi pull on a 14b /ubbthreads/images/graemlins/dunno.gif

 

[BoostedAWD91]

well i did a compression check today.
#4- 140psi
#3- 150psi
#2- 148psi
#1- 148psi

Not perfect but not bad enought to cause any problems. I just dont understand why im not getting any power anymore. Any ideas what else it could be?

 

[BoostedAWD91]

Update:
I got rid of pretty much all the bogging and jerking but it still does it some until it is completly warmed up. The weird part is that when it was bogging down badly, it was still running rich and i had to add 10% more fuel to get it to run right and to stop the bogging down. So right now it is running extremely rich which i shouldnt have to be doing. There has to be another issue somewhere that im having to compensate for.

 

[Yao]

Well, I guess it's time for me to chip in. When I first start to modify the GVR4 back in 92 there wasn't anything available except the PFC-FCON and VPC. VPC for Eclipse GSX and PFC-Fcon for Gvr4. I feel that Eclipse and Gvr4 is close enough that I tried the VPC for my VR4. I tell you what, IT WAS THE BIGGEST/Most Expensive piece of sh*t tunning tool I have ever wasted my money on. Never run right, always hiccuping or bogging or jerking when tip in throttle, I HATE THAT HKS sh*t!!!! Yeah, did I mention the time I put into make it work??! over 3 years with it and nothing but problems not to mention the constant jerking causing constant shock to my driveline that caused me even more problems and money! Yes, the second I got it off the car, 100x better! This was back then, without much options, but now... you have so much! pick anyone and it will work better.

 

[atc250r]

It must have been something with the harness or something. I've got a VPC in mine and it runs nearly flawlessly. The only problem is a very slight lean spot on tip in but other than that its perfect.

John