SLOPONY

I have a 2009 Silverado with a 4.8. The previous owned stuffed a 232/238 .625 112 lsa cam in it. It runs awesome, drives awesome, and I am not changing out the cam...

however, I get a **** brake pedal and service traction control, and service stabilitrak lights and tones often while braking, or coming off the throttle due to the low vacuum. I added a vacuum canister, and that helped some with pedal feel, then I added a vacuum pump and the brakes work awesome, but I think it provides too much vacuum at times when the computer thinks it should see less, like at part throttle, and wide open throttle. NO WIN situation for me as the damn lights, and tone are driving me nuts to the point that the truck is parked.

I tried removing the abs fuse, but that makes the pedal rock hard regardless of the can and pump, I tried bypassing the sensor, but that makes more lights and tones come on.

I have most of the parts to do a hydroboost swap, but I am concerned that the ABS module will still not allow the brakes to function correctly as that vacuum sensor will no longer be in the system.

Does any one know how to bypass the sensor so the brakes will work as they should, or setup the truck some way that the brakes work, and I don't get a constant barrage of tones and flashing lights?

madmann26

iTrader: (7)

Sounds like the tune could use some work.


or..


Change the cam. LOL (had to).

rennat_2006

iTrader: (10)

Its gonna happen with that cam with the low vacuum. I went through this exact same issue with the first cam i was recomended for my wifes 08 suburban i did the dod delete on.

Only thing i can think of to get away from it would be flashing whatever module that vacuum sensor is part of (bcm maybe?) Because i dont see anything for it in the ecm with my efi live and flashing yours to a 2500 tune that does not have that vacuum sensor/or uses a hydroboost setup.

SLOPONY

Nothing in the tune that I know of can be corrected to fix it with HP tuners. I assume it is in the BCM, but even then with the latest mac scan tool connected while the error occurs,...nothing shows up. No codes, no issues via the scan tool.

Any one know how to disable the chime? LOL

smokeshow

iTrader: (16)

HPT doesn't display everything.

vettelovralexand

It wont fix everything but turning the idle speed up should help.

rennat_2006

iTrader: (10)

Not really, probably a little less vacuum actaully cuz the throttle blade will be cracked open further.

vettelovralexand

While true that the throttle opens more the vacuum will still increase. If you have a gauge or a scanner to monitor MAP, you are more than welcome to test it yourself. Give it enough gas to hold steady at higher than current idle speed and the vacuum will rise (or MAP will drop).

hernandez_dm

Having the same issue after doing a cam swap on my truck, hopefully anyone finds a fix

310reaper

I have the same issue with a Texas speed (214/222, .550"/.550", 108 LSA, 106 ICL) CAM; the vacuum is around 13-14. I check for leaks. I also have a new booster and master cylinder. We have returned it several times. I checked everything. I’m to the point I want to order an electric vacuum pump.

The truck runs great, and I’m running a factory stall bedside; the issue with the low vacuum and the breaks feeling crappy.