Trying to solve my BLM issue

cjmatt

Moderator
Joined
Aug 31, 2007
Well here is my issue...

The car at idle is running BLM's of 150. If I rev it up or give it some gas while driving it will drop back down to the 130-140s and if Im giving it a decent amount of gas it is at 128, but low throttle cruising always goes back up to 150.

In my pursuit to fix it, the first thing I did was vicegrip the pcv hose shut by pinching it. It didnt change anything.
The second thing I did was remove the vacuum block from the top of the motor and made a makeshift block off gasket out of duct tape that closed off all of the vacuum from reaching the block. this time when I fired it up, the car was running eyeburningly rich at idle with blms of 100. So next I removed that gasket and cut out a little hole...this would now only allow vacuum to everything except the PCV, this time the rich issue went away and confirmed to me that it was not pcv related as it was still blocked off, yet no longer running rich.

Now ive got most of the ports on the block taped off trying to diagnose where this is coming from. the only things I have hooked up are the one line that runs to my map sensor/boostgauge/boost solenoid for my MAFTPRO and another port that runs to the fuel pressure regulator.

based on the fact that the boost gauge seems to be working fine, i dont think there is a leak in that harness either, plus it is all new with ziptied lines and whatnot, the only line it could be in is the fuel pressure regulator line and that seems to be working as well. I have upgraded to the aftermarket billet one, but the lines are all stock, should i remove the factory one-way-valve looking parts from it?


Any help is greatlyt appreciated as this is keeping me from really being able to tune this thing right. I cannot get the IAC numbers low enough to even set the TPS correctly, if i compeletely pull off the iac screw so the TB closes, my IAC is still at mid 80s

Could this be related to my maftepro or extender chip? i dont seem to remember having these problems at idle on my stock chip or injectors. Ive got another 60lb chip laying around that I may have top pop in to see how it reads. right now my idle O2s are around 150-200, which i didnt think it would even run at.

Any help would be appreciated because it is causing driveablity issues once warmed up, it wants to stall out if you dont give it any gas.
 
With the MAFPRO, if you block off the MAP line, it's going to go pig rich because it calculates fuel based on that. So you can't use that as a test.

On the IAC, you are going the wrong way. If you back out the screw to close the blade, the IAC will get higher and higher. You need to open the blade so the IAC will go lower.

For the high BLM at idle, in the MAFPRO, increase the low load fuel adjustment until the BLM starts coming down.

Regards,
Eric
 
With the MAFPRO, if you block off the MAP line, it's going to go pig rich because it calculates fuel based on that. So you can't use that as a test.

On the IAC, you are going the wrong way. If you back out the screw to close the blade, the IAC will get higher and higher. You need to open the blade so the IAC will go lower.

For the high BLM at idle, in the MAFPRO, increase the low load fuel adjustment until the BLM starts coming down.

Regards,
Eric
Wow, im an idiot, I never thought of the map sensor issue. Well I guess that solves that issue

How much fuel should I be adding at the low load? Ive gone as high as 15% and it doesnt change from 150

Does the MAFTPRO adjust the idle from the low load setting or is it a totally different table?
 
I would be tempted to add around 5% to the mainscale since all your BLM's were a tad high. Then go back and keep adding to low load.
 
Does the MAFTPRO adjust the idle from the low load setting or is it a totally different table?

You'll have to watch your map reading vs. the map cutoff you specify for the low load table. If you meet the map and tps parameters then that is the table you are working with to adjust idle fuel. I have seen times when my idle map exceed the low table cutoff and pushed idle into the mid load table settings.

Mike
 
well i'll mess with it tonight, try to adjust my throttle blade open enough to get my IAC and TPS settings inline. I didnt realize that being that im MAFless, vacuum leaks dont really effect me other than raising my idle as its not missing any air through the maf
 
I have a couple blm issues which maybe Eric can figure out. Should help you too cjmatt. On one car blm is 135 and I have an extender chip, basic translator and LT1 Maf. I fixed some vacuum leaks and I can't find any more. I was told by an old time Buick guru not to worry about it, could be the gas with ethanol preventing it from going to 128. Any thoughts on this? Now, on my other GN, blm is 118. It has 009's, basic translator and LT-1 Maf. I tried turning down the fuel pressure, tried turning up the fuel pressure, and blm stayed at 118. I have a TT chip on this car. Should I be concerned or is this normal?
 
yeah, id be curious to know how e85 effects the 02 readings as one of my plans this summer is to convert to an e85 tune
 
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