PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

BLM question Park vs. Drive

Thread Tools
 
Search this Thread
 
Old Sep 17, 2009 | 06:52 PM
  #1  
C_Rules's Avatar
Thread Starter
12 Second Club
iTrader: (7)
 
Joined: Oct 2005
Posts: 1,666
Likes: 0
From: NYC
Default BLM question Park vs. Drive

Why would a car have the BLMs very close in the park position but split widely in gear?
Reply
Old Sep 17, 2009 | 09:13 PM
  #2  
Doc99SS's Avatar
TECH Regular
iTrader: (2)
 
Joined: Nov 2001
Posts: 456
Likes: 0
From: Mims, Florida
Default

BLM = Block Learn Memory; in our OBDII cars we call that LTFT = Long Term Fuel Trim..

But to answer your question, I would guess that one clogged injector would do this. The clogged injector can squirt enough fuel at idle, but not enough at higher RPM. Run some fuel injector cleaner thru your gas and so if anything changes for you.
Reply
Old Sep 18, 2009 | 12:32 AM
  #3  
JonCR96Z's Avatar
TECH Junkie
20 Year Member
Photogenic
iTrader: (33)
 
Joined: Jan 2003
Posts: 3,006
Likes: 19
From: Asheboro, NC
Default

Originally Posted by Doc99SS
BLM = Block Learn Memory; in our OBDII cars we call that LTFT = Long Term Fuel Trim..

But to answer your question, I would guess that one clogged injector would do this. The clogged injector can squirt enough fuel at idle, but not enough at higher RPM. Run some fuel injector cleaner thru your gas and so if anything changes for you.
BLM = Block Learn Multiplier. And I think he's talking about idling in both park and in gear.

C-Rules: What are the IAC counts and commanded idle speed both in park and in gear? I've seen cases where adjusting the throttle stop and changing the IAC counts can skew BLMs one way or the other. Also, what throttle body?
Reply
Old Sep 18, 2009 | 07:47 AM
  #4  
C_Rules's Avatar
Thread Starter
12 Second Club
iTrader: (7)
 
Joined: Oct 2005
Posts: 1,666
Likes: 0
From: NYC
Default

Originally Posted by JonCR96Z
BLM = Block Learn Multiplier. And I think he's talking about idling in both park and in gear.

C-Rules: What are the IAC counts and commanded idle speed both in park and in gear? I've seen cases where adjusting the throttle stop and changing the IAC counts can skew BLMs one way or the other. Also, what throttle body?
i'll have to check the IACs and get back to you on that. in drive my idle is 900 and in park its 1050. I have a 58mm bbk. the injectors are good because i just recently had them cleaned and flow tested.
Reply
Old Sep 20, 2009 | 05:49 PM
  #5  
C_Rules's Avatar
Thread Starter
12 Second Club
iTrader: (7)
 
Joined: Oct 2005
Posts: 1,666
Likes: 0
From: NYC
Default

i checked them. 39 in park and 75 in gear. turns out the split happens either in park and drive so my above statement was incorrect. i took a log and analyzed real well.

another question i have is what could cause a car to have split blms in SD mode but not when running a MAF?
Reply




All times are GMT -5. The time now is 11:41 PM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE