Will size of cam affect blm's?

[GNRick]

My mechanic says it would. He also said blm's can be affected by outside temperature, even the gasoline. So this leads into the following problem- I'm trying to get blm's down to 128. I have a stock cam. I adjusted the tps to .42 (from .40) at idle and that brought blm down to 135 from 138. Then I added 10% fuel at idle, in translator, and that brought it down to 128. I thought I had it licked.....drove around about 10 miles, blm went back to 138. Integrator is right around 128-133. Also, mechanic had smoked the car and said the only leak was at the throttle body shaft seal, which he repaired with a new seal. I'm thinking of having him smoke it again, only maybe spending a little more time on it this time. I don't know how long he spent on it last time but I suspect it wasn't long enough. What do you guys think? there must be a vacuum leak, right? Maybe it's leaking behind the climate control in the dash and he didn't check inside the car.

 

[chopped39]

could be the lower intake. block off pcv and all breathers and install vacuum guage on dipstick tube and see if it pulls any vacuum.Some times you need a magnehelic gage for low vacuum that a regular gauge wont pick up. sounds stupid and simple but it works. remove or block off all sources of vacuum from the engine to the cruise and the heater control and see what happens.

 

[83ttypecooled]

Hi,
I don't think it is that important to be dead nuts on 128 with the block learn. It's a number,and will fluctuate with the function of your motor. Don't freak out over small variations. 138 is a small correction in the way of things. You might add some fuel pressure to fix the issue.

 

[GNRick]

Hi,
I don't think it is that important to be dead nuts on 128 with the block learn. It's a number,and will fluctuate with the function of your motor. Don't freak out over small variations. 138 is a small correction in the way of things. You might add some fuel pressure to fix the issue.

I added 10% fuel in the translator but that was just a temporary fix. If all it takes is a little vacuum hose then I would like to fix it. It can only get worse if another leak should appear later. If it requires removing the lower intake then I would leave it alone. If it's something like an injector O ring then I would fix it. I realize there are bigger problems in this world than my BLM's.

 

[83ttypecooled]

Hi,
I think it is likely that as our motors age,they tend to use more fuel. They are prone to the same thing that happens to us,which is entropy,basically. I can imagine lots worse than a couple of clicks up on the block learn. We compensate,and your vehicle does too. No big deal.

 

[Adam Connell]

I've been chasing my BLMs at idle as well here recently. My search did lead me to several nice vacuum leaks, which in turn made a nice difference in how my car feels at low rpm and I think I've seen an mpg difference.

But Im still chasing a BLM at idle in the mid 130's, do you think this might be a vacuum leak still?

Either way, my car is much happier, so I'll second checking all vacuum sources.

I dont know who posted, or made this, but this was extremely helpful!
http://i216.photobucket.com/albums/cc31/earl87gta/86 Buick GN/vac_federal.jpg

I will eventually completely redo all of my vacuum lines and check valves, but for the first time in a long time my dash boost gauge is relatively accurate

 

[berserker6]

like 83ttype said. just a small bump in fuel pressure can get you close. what is your fuel pressure set at with the vacuum line removed?

 

[TurboBuRick]

Your mechanic is right. There are allot of variables. Vacuum leaks, pcv, other leaking components, fuel pressure, weather, even maf orientation to the intake pipe. Have you tried re-clocking (turn) the maf?

If you don't already have one, a handheld vacuum pump is a helpful tool for tracking down leaks.

Another thing you can do is unplug the vacuum lines and cap them 1 at a time. Watch the blm's for a big jump.

IMO 10 + or - 128 is really nothing to worry about.

HTH

 

[GNRick]

like 83ttype said. just a small bump in fuel pressure can get you close. what is your fuel pressure set at with the vacuum line removed?

I set it at 45 line off, per chip instructions. Again, I bumped up FP in translator at idle. BLM went to 128 but then back to 138 after driving a few miles. I've capped off the lines connected to the vacuum block on the throttle body one at a time. Didn't work.

 

[GNRick]

Your mechanic is right. There are allot of variables. Vacuum leaks, pcv, other leaking components, fuel pressure, weather, even maf orientation to the intake pipe. Have you tried re-clocking (turn) the maf?

If you don't already have one, a handheld vacuum pump is a helpful tool for tracking down leaks.

Another thing you can do is unplug the vacuum lines and cap them 1 at a time. Watch the blm's for a big jump.

IMO 10 + or - 128 is really nothing to worry about.

HTH

I do have a hand held pump. Will try it. Haven't tried turning the MAF. Will try it too. Thanks! anybody know if a larger cam would affect blm's? (My cam is stock).