Idle lean condition
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
Likes: 0
Idle lean condition My Setup:
408
Heads: 2.055/1.6
Cam: 238/242 .610
LS6 Intake
85mm MAF Ends
FLP Headers
Vacuum referenced Fuel pressure regulator (Set to 43psi @ idle)
42# Injectors
Problem:
Car runs decent when first started then when it gets hot and goes into closed loop it goes lean, wideband shows over 17:1 AFR and car starts to sputter. I have tuned these injectors on a non-heads/cam car in the past with no problems.
Open loop start: 13's AFR
Goes into closed loop and kind of works its way lean
Here is how I have scaled my IFR table: 5.29 across the board
Does this sound right?
408
Heads: 2.055/1.6
Cam: 238/242 .610
LS6 Intake
85mm MAF Ends
FLP Headers
Vacuum referenced Fuel pressure regulator (Set to 43psi @ idle)
42# Injectors
Problem:
Car runs decent when first started then when it gets hot and goes into closed loop it goes lean, wideband shows over 17:1 AFR and car starts to sputter. I have tuned these injectors on a non-heads/cam car in the past with no problems.
Open loop start: 13's AFR
Goes into closed loop and kind of works its way lean
Here is how I have scaled my IFR table: 5.29 across the board
Does this sound right?
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
Likes: 0
Yeah but if I have it tuned for 43psi then it should be ok shouldnt it? Well, I am going to go ahead and pull the vacuum line off the regulator and set it to 58-60psi and try tuning for that...I will report back
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
also running 5.29 across the board may be a problem... the stock IFR table is scaled small to large
to get a proper IFR table first scale the 42lbs to what they are at 4 bar
(58/43.5)^.5 = 1.1547005383792515290182975610039
so 42lb injectors at 4 bar run at 48.5 lb/hr
now determine how much larger those are than stock
if 26lb stock (99-00) then = 1.865 larger
if 28lb stock (98, 01-02) then = 1.73 larger
(assuming f-body)
so multiply the stock IFR table by the appropriate value
But I bet the Fuel Pressure is the main culprit... as scaling the stock IFR using the percentages above will lean it out even more (your 5.29 value will run richer at 60psi than the scaled values at 60psi, but 5.29 at 43psi will run leaner than at 60psi)
to get a proper IFR table first scale the 42lbs to what they are at 4 bar
(58/43.5)^.5 = 1.1547005383792515290182975610039
so 42lb injectors at 4 bar run at 48.5 lb/hr
now determine how much larger those are than stock
if 26lb stock (99-00) then = 1.865 larger
if 28lb stock (98, 01-02) then = 1.73 larger
(assuming f-body)
so multiply the stock IFR table by the appropriate value
But I bet the Fuel Pressure is the main culprit... as scaling the stock IFR using the percentages above will lean it out even more (your 5.29 value will run richer at 60psi than the scaled values at 60psi, but 5.29 at 43psi will run leaner than at 60psi)
Last edited by horist; Jan 11, 2005 at 12:14 PM.
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
Likes: 0
I pulled the vacuum line off the regulator, scaled my stock tables to around 6.20 up to maybe 6.60 and it did the same thing. Then I was told to replce my 02 sensors because last motor I had I blew a head gasket and they were probably in rough shape from all the coolant in the exhaust. So I did that and the same thing still happens.
I start the motor...runs fine for about 1 minute idling at about 13's AFR and then slowly starts to lean out until the wideband cant read it anymore. Seems like it starts to lean out when it goes into closed loop
I start the motor...runs fine for about 1 minute idling at about 13's AFR and then slowly starts to lean out until the wideband cant read it anymore. Seems like it starts to lean out when it goes into closed loop
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
keep in mind the higher that IFR value is the leaner it runs... hence why if you put large injectors in w/the stock IFR it runs so rich it won't run I'd try the IFR for the injectors lower around 5.80
How about your LTRIMs ? are they maxing (PCM adding as much fuel as it can) aat idle?
You've checked for any vacuum leaks also correct? (any vacuum leaks post MAF)
How about your LTRIMs ? are they maxing (PCM adding as much fuel as it can) aat idle?
You've checked for any vacuum leaks also correct? (any vacuum leaks post MAF)
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
closed means it is monitoring all sensors and computer has complete control. open loop is predtermend tables with few sensor input..
open loop is cold starts, and wot.
closed loop is when up to temp and the computer is controlling timng and fuel..
open loop is cold starts, and wot.
closed loop is when up to temp and the computer is controlling timng and fuel..
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
Likes: 0
wait4me hit it on the head
I found the problem. There was a leak in the PCV area and the air pump was still on, when I thought I had disabled it in Edit. Now the A/F adjustments work with the IFR table and VE table and is running pretty nice. Also had to drill a monster size hole the the throttle body. At first I had tried to do the set screw trick but that didnt work well.
The AFR is decent, but my IAC's fluctuate a lot and when I am real low speed, barely on the pedal, in gear driving, or when I start to come to a stop, it surges quite a bit. IAC's range from 40's to 60's. And they were originally in the 150's. The TB hole is a little over 1/4"!!
But other than that, when I am above 15mph or so it runs fine. Or when I am idling in neutral it sounds good.
Any suggestions for the surging?
I found the problem. There was a leak in the PCV area and the air pump was still on, when I thought I had disabled it in Edit. Now the A/F adjustments work with the IFR table and VE table and is running pretty nice. Also had to drill a monster size hole the the throttle body. At first I had tried to do the set screw trick but that didnt work well.
The AFR is decent, but my IAC's fluctuate a lot and when I am real low speed, barely on the pedal, in gear driving, or when I start to come to a stop, it surges quite a bit. IAC's range from 40's to 60's. And they were originally in the 150's. The TB hole is a little over 1/4"!!
But other than that, when I am above 15mph or so it runs fine. Or when I am idling in neutral it sounds good.
Any suggestions for the surging?
Originally Posted by SSkeet
wait4me hit it on the head
I found the problem. There was a leak in the PCV area and the air pump was still on, when I thought I had disabled it in Edit. Now the A/F adjustments work with the IFR table and VE table and is running pretty nice. Also had to drill a monster size hole the the throttle body. At first I had tried to do the set screw trick but that didnt work well.
The AFR is decent, but my IAC's fluctuate a lot and when I am real low speed, barely on the pedal, in gear driving, or when I start to come to a stop, it surges quite a bit. IAC's range from 40's to 60's. And they were originally in the 150's. The TB hole is a little over 1/4"!!
But other than that, when I am above 15mph or so it runs fine. Or when I am idling in neutral it sounds good.
Any suggestions for the surging?
I found the problem. There was a leak in the PCV area and the air pump was still on, when I thought I had disabled it in Edit. Now the A/F adjustments work with the IFR table and VE table and is running pretty nice. Also had to drill a monster size hole the the throttle body. At first I had tried to do the set screw trick but that didnt work well.
The AFR is decent, but my IAC's fluctuate a lot and when I am real low speed, barely on the pedal, in gear driving, or when I start to come to a stop, it surges quite a bit. IAC's range from 40's to 60's. And they were originally in the 150's. The TB hole is a little over 1/4"!!
But other than that, when I am above 15mph or so it runs fine. Or when I am idling in neutral it sounds good.
Any suggestions for the surging?
ve table needs more out of it, or unplug your maf, if it stops surging, then plug it back in and take alittle out of the maf sensor at idle rpms, "make up for changing the intake tract" then you shouldbe all set
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
Likes: 0
wait4me, i will try what you say...so you mean take out some in the MAF table for low Hz values? Like maybe the first 6-7 columns?
Yeah it took 1/4" to get the IACs to 40's. I will try the VE and MAF stuff a little...
Yeah it took 1/4" to get the IACs to 40's. I will try the VE and MAF stuff a little...
if your car ran better at a different iac that that would have been ok, 40 is just a number that puts you in the middle of the iac range.. somecars just dont like running there.. every car is different. jes