PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

AFR Errors

Thread Tools
 
Search this Thread
 
Old Oct 3, 2012 | 07:53 AM
  #1  
LS1Silverado05's Avatar
Thread Starter
TECH Addict
20 Year Member
Photogenic
Photoriffic
Liked
iTrader: (41)
 
Joined: Jun 2005
Posts: 2,370
Likes: 1
From: Classified
Question AFR Errors

After chasing what appeared to be a lean issue to exhausting lengths (Blocked EGR, cleaned MAF, New plugs, wires, intake gaskets, new fuel filter etc) , I started on Calibrating the MAF. This car is a stock car with exception of a Walbro pump and someone has descreened the MAF. I was seeing 18% AFR error at idle with a commanded 12.5. After applying the % correction to the idle cells in the airflow/hz table, my error was -1 to 1. So the correction appeared to take hold, however my question is, does that sound possible without a physcial motor problem or air leak? I am new to tuning but 18% off at idle just seems high on an un-modified car on a stock tune (verified).

Please give me your thoughts on % error and what is a reasonable error to see while dialing in tables. I dont want to just dump fuel on top of a problem, but if it sounds possible without a problem being present I will continue my MAF Cal.

Thanks
Reply
Old Oct 3, 2012 | 07:56 AM
  #2  
Chevy406's Avatar
9 Second Club
iTrader: (12)
 
Joined: Feb 2007
Posts: 781
Likes: 11
From: Huntsville, AL
Default

If you don't have vacuum or exhaust leaks then give the engine the fuel it wants.
Reply
Old Oct 3, 2012 | 07:59 AM
  #3  
LS1Silverado05's Avatar
Thread Starter
TECH Addict
20 Year Member
Photogenic
Photoriffic
Liked
iTrader: (41)
 
Joined: Jun 2005
Posts: 2,370
Likes: 1
From: Classified
Default

Originally Posted by Chevy406
If you don't have vacuum or exhaust leaks then give the engine the fuel it wants.
Thanks for the reply... Yeah it sure doesnt appear to have any exhaust leaks or vacuum leaks. But it idles a little bit rough which makes me think there is. Then again maybe it idle rough because its busy correcting.
Reply
Old Oct 3, 2012 | 08:03 AM
  #4  
Chevy406's Avatar
9 Second Club
iTrader: (12)
 
Joined: Feb 2007
Posts: 781
Likes: 11
From: Huntsville, AL
Default

I recently tuned a '99 Corvette that was pretty much stock. It required a lot of MAF adjustment to drop the fuel trims. I couldn't find a vacuum leak so I modified the table as required. I don't know if it was a replacement MAF sensor that had a different calibration or what.
Reply
Old Oct 3, 2012 | 08:06 AM
  #5  
LS1Silverado05's Avatar
Thread Starter
TECH Addict
20 Year Member
Photogenic
Photoriffic
Liked
iTrader: (41)
 
Joined: Jun 2005
Posts: 2,370
Likes: 1
From: Classified
Default

Ahh ok. Maybe im banging my head against the wall for nothing. Just assumed that was way off for a stock car. RPMs are steady at 850-900 too so I wouldnt think I have a vacuum leak or I would be having a higher idle too?

Ill keep tuning on this MAF a bit. Any advice on what AFR to shoot for at idle?
Reply
Old Oct 3, 2012 | 09:12 AM
  #6  
outkast6991's Avatar
TECH Fanatic
iTrader: (34)
 
Joined: Jun 2004
Posts: 1,625
Likes: 0
From: lancaster,pa
Default

wouldn't stoich be a good target on a stock car?
Reply
Old Oct 3, 2012 | 09:21 AM
  #7  
LS1Silverado05's Avatar
Thread Starter
TECH Addict
20 Year Member
Photogenic
Photoriffic
Liked
iTrader: (41)
 
Joined: Jun 2005
Posts: 2,370
Likes: 1
From: Classified
Default

Originally Posted by outkast6991
wouldn't stoich be a good target on a stock car?
Well thats my assumption yeah.. Just wanted to see if there were other schools of thought.

I only have it commanding the 12.5 for simplicity of tuning the MAF across the board for the moment...
Reply
Old Oct 3, 2012 | 10:11 AM
  #8  
BLK02WS6's Avatar
9 Second Club
iTrader: (2)
 
Joined: Jul 2002
Posts: 2,583
Likes: 1
From: on the dyno tuning in MD
Default

Originally Posted by LS1Silverado05
someone has descreened the MAF.
There would be your problem...
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

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

 Verdad Gallardo
story-1

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-2

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-3

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-4

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-5

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-6

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-7

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-8

10 Camaros You Should Never Buy

 
story-9

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
Old Oct 3, 2012 | 10:13 AM
  #9  
LS1Silverado05's Avatar
Thread Starter
TECH Addict
20 Year Member
Photogenic
Photoriffic
Liked
iTrader: (41)
 
Joined: Jun 2005
Posts: 2,370
Likes: 1
From: Classified
Default

Originally Posted by BLK02WS6
There would be your problem...
Think so? Will it be fine once I re-calibrate? Or should I be sourcing a replacement?

Is that proof that it flows more? LOL. Albeit not smooth flow?

Last edited by LS1Silverado05; Oct 3, 2012 at 10:18 AM.
Reply
Old Oct 3, 2012 | 06:37 PM
  #10  
BLK02WS6's Avatar
9 Second Club
iTrader: (2)
 
Joined: Jul 2002
Posts: 2,583
Likes: 1
From: on the dyno tuning in MD
Default

Originally Posted by LS1Silverado05
Think so? Will it be fine once I re-calibrate? Or should I be sourcing a replacement?

Is that proof that it flows more? LOL. Albeit not smooth flow?
No, it flows different, not more - the screen is there to take away turbulence so the readings are smoother and flow is even across the cross section of the MAF. You can try to recalibrate it and as long as you get a smooth table and smooth readings, that's fine. If it gives you fits, I would get another. BTW a stock screened MAF is good up to around 450 rwhp before it becomes a restriction - been proven many times...
Reply
Old Oct 3, 2012 | 07:45 PM
  #11  
LS1Silverado05's Avatar
Thread Starter
TECH Addict
20 Year Member
Photogenic
Photoriffic
Liked
iTrader: (41)
 
Joined: Jun 2005
Posts: 2,370
Likes: 1
From: Classified
Default

Originally Posted by BLK02WS6
No, it flows different, not more - the screen is there to take away turbulence so the readings are smoother and flow is even across the cross section of the MAF. You can try to recalibrate it and as long as you get a smooth table and smooth readings, that's fine. If it gives you fits, I would get another. BTW a stock screened MAF is good up to around 450 rwhp before it becomes a restriction - been proven many times...
Im with ya... I was kind of being a smartass, Ive never prescribed to the de-screen idea.

After some tweaking I got my errors to dial in some.... far from finished but...
Reply




All times are GMT -5. The time now is 10:29 AM.

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