I just put my truck back to stock after having a supercharger on it and it's not running right. I've already re-flashed the tune. I think I have it narrowed down to a vacuum problem but I'm not completely sure.

The big problem is the brakes aren't working!!

I have essentially no brakes 75% of the time. I have to stand on the brakes to get the truck to stop but there are some random times that they will work just fine and normal. Since the brake booster is hooked up to vacuum my assumption is it is all related.

There is no pick up in acceleration, a prius would outrun my truck right now. I have a wideband 02 sensor and the truck goes dangerously lean on acceleration.

I have a vacuum/boost gauge and it shows about 11psi of vacuum which is probably low however it was only at 11psi while supercharged, and as long as I've had the truck. The truck ran great before and while supercharged.


I'm not sure of any other helpful descriptions but it has me puzzled. I got under the hood of another '04 supercrew to see how his lines were run and everything looks normal to me. Can anyone confirm that this sounds like a vacuum problem, and are there any good ways to test and pinpoint where my problem is at?

 

My truck idles at 20 psi on my vac/ boost gauge that's the norm I'm pretty sure. As for finding the leak check re check all your lines maybe one is broke or one is not connected right

 

I knew 11 isn't "normal" but it's always been like that and there has never been any problem. I did what I could to check them out, I unhooked the line going into the brake booster and I could feel vacuum there, and there is vacuum at the fuel rail. I didn't see any leaks around the intake. I was a little concerned something in the back of the intake manifold was messed up because I had removed the manifold for the whipple supercharger manifold, so I'm hoping there is some type of test I can do myself without ripping everything apart just guessing.

Does anyone have a map of the vacuum lines?

 

Does it idle any better when you plug the line going to the brake booster?
Could be a leak in the brake booster diaphragm. Intake gasket leak?

 

I sprayed carb cleaner all around and was able to find a leak at the throttle body. I felt really dumb when I realized I didn't put the stock gasket back in, I left it with my supercharger when I sold it. I got a new gasket and the truck now idles just fine and the a/f ratio is perfect at idle.

I still have the issue of the brakes not working and it's going very lean under throttle with essentially no acceleration. It's at 12psi of vacuum at idle, I tried messing with a bunch of different lines to try and diagnose but I'm still at a loss for what's going on. There is 11psi of vacuum going into the brake booster and the check valve seemed just fine, I have no clue how to test the diaphragm. I messed with the check valve behind the battery but I don't really know how to test it.


Anyone else have some advice!?

 

Pulled the intake manifold tonight to see that the hose connecting from the intake manifold on drivers side to the brake booster had a kink in it which was impeding enough vacuum to cause my brakes to stop working.

Brakes now work, engine is still lean which explains the lack of acceleration. I'm going to get new 02 sensors and see what happens. Thanks for the advice