Why would a car have the BLMs very close in the park position but split widely in gear?

 

Mine are the opposite, they run about 136/124 in park but 128/128 in gear. Just chalk it up to the change in vacuum/rpm/load changing whats going on in the manifold.

 

We need to know more about your setup to get into specifics.

It is the same for me. When you have all of your idle air going through the IAC and idle plenum, the air is controlled better at each individual cylinder. This is what happens in park and no throttle if your blades are set up to be completely closed.

Now you give it some gas and air goes through the TB blades, it cannot be so easily controlled at part throttle to go to each cylinder evenly. The vacuum causes this. The larger the cam (reversion back into the intake plenum) the larger the split.

At WOT, you have atmospheric or close to atmospheric conditions so again this issue with split BLM's goes away.

Ben

 

good explanation, thanks. the weirdest thing is that i had my BLMs nearly perfect while running my car with the MAF and leaning out cylinder 7 to .86. went to do an SD tune on it and both sides were at 108 as i started leaning the ve tables out using VE master the split came back.