Car won't idle in open loop!
Thread Starter
TECH Veteran
iTrader: (53)
Joined: Feb 2004
Posts: 4,433
Likes: 0
From: Monticello, Kentucky
Car won't idle in open loop! I assume this because after it warms, it will idle. By the time it warms, it's in closed loop. I made only two changes when this started (well, three)--I simply upped my injector constant to lean things out a tad and uploaded a new STOCK MAF table to accompany my stock MAF I just put in. I'm not changing any of that back so I was wanting a tuning tip or two.
MAF is not the only actor at idle; the speed-density
tune may have more to do with it. Leaning the injector
table out, wholesale, may have hurt. Then again, I know
diddly-squat about LT1s. But happiness seems to be found
in the low end of the VE table, for the cam & headers guys,
chasing idle problems. I think you should scale the injector
table for theoretical delivery, and have MAF table match
MAF, and tweak on the corner-specific bits (VE for idle,
PE vs RPM for the big end) unless you see a consistent
across-the-board fuel error that -might- be better fixed
by gangwise messing the injector table around.
Might be good to disconnect the batt, zeroing all trim
stuff, and force it do do idle relearn; just let it die and
crank again, etc., while it's still cold, and it may find its
way home?
tune may have more to do with it. Leaning the injector
table out, wholesale, may have hurt. Then again, I know
diddly-squat about LT1s. But happiness seems to be found
in the low end of the VE table, for the cam & headers guys,
chasing idle problems. I think you should scale the injector
table for theoretical delivery, and have MAF table match
MAF, and tweak on the corner-specific bits (VE for idle,
PE vs RPM for the big end) unless you see a consistent
across-the-board fuel error that -might- be better fixed
by gangwise messing the injector table around.
Might be good to disconnect the batt, zeroing all trim
stuff, and force it do do idle relearn; just let it die and
crank again, etc., while it's still cold, and it may find its
way home?
FormerVendor
Joined: May 2004
Posts: 152
Likes: 0
Originally Posted by dhdenney
I assume this because after it warms, it will idle. By the time it warms, it's in closed loop. I made only two changes when this started (well, three)--I simply upped my injector constant to lean things out a tad and uploaded a new STOCK MAF table to accompany my stock MAF I just put in. I'm not changing any of that back so I was wanting a tuning tip or two.
Hi guys.
On the LT1 it's either MAF or speed density. The VE tables are not used to calculate the airflow on the LT1 in MAF mode. There is another table used in in MAF mode (MAF LOAD) to calculate the ariflow transients for transient fuel, but it wont be the the reason the car won't idle.
First step is to set the injector constant to match the injectors. If you have some fine tuning issues, use the MAF table to make small adjustments.
It almost sounds like you have an air leak in the MAF ducting, or IAC problems. The only way you are going to find this is to make sure all of the components on the vehicle are in working order (incuding O2 sensors), then start logging some data when the problem occurs.
If the PCM is having to make major adjustments to run in closed loop, it will screw up your open loop startup.
Ken
HP Tuners
Thread Starter
TECH Veteran
iTrader: (53)
Joined: Feb 2004
Posts: 4,433
Likes: 0
From: Monticello, Kentucky
Should I increase or decrease my curve in the MAF table? I did have a bigger curve (higher numbers) in there but when I went stock I changed it back to stock. On the injector constant, I increased it a little to lean it. I'm using too much gas! I can't really log any runs because my laptop is a piece of **** so I'm limited to desktop changes and no runs. Could I get away with just reving the thing and letting it log then? Or my numbers wouldn't be as accurate?
FormerVendor
Joined: May 2004
Posts: 152
Likes: 0
Originally Posted by dhdenney
Should I increase or decrease my curve in the MAF table? I did have a bigger curve (higher numbers) in there but when I went stock I changed it back to stock. On the injector constant, I increased it a little to lean it. I'm using too much gas! I can't really log any runs because my laptop is a piece of **** so I'm limited to desktop changes and no runs. Could I get away with just reving the thing and letting it log then? Or my numbers wouldn't be as accurate?
the ability to log data and see what is wrong.
Two things are real imortant when trying to sort this stuff out.
The MAF table must match the MAF airlow curve you are using.
The only reason to change the MAF curve is when you change to a new MAF with a different curve or screw with the stock MAF and descreen it and change the intake ducting to upset the airflow. If you are using a straight intake duct with no bends you can ditch the MAF screen without issues.
The screen is only there to straighten out the airflow turbulence caused by bends in the intake system.
The Injector flow rate must match the actual rate by your injectors including any increased flow due to higher fuel pressure.
If you are still way too rich with both of those set correctly, then something is broken. The PCM cannot calculate the fuel rate to the engine if it cannot accurately measure the airflow and know what the exact injector flow rate is.
Just out of curiousity, are you rich all the time or just during a WOT run?
If you are just rich at WOT, then your PE tables need to be adjusted.
I don't know how much of a POS your laptop really is, but Datamaster does not require a lot of CPU overhead to log what you need. It will run on a 90 MHZ laptop with 32mb ram. You can also use their program in demo mode for
20 sessions before you have to buy it.
If your engine is running that rich, a new "used" laptop is cheaper than an engine rebuild due to washed out rings.
Ken
Thread Starter
TECH Veteran
iTrader: (53)
Joined: Feb 2004
Posts: 4,433
Likes: 0
From: Monticello, Kentucky
Originally Posted by Super Sport X2
Just out of curiousity, are you rich all the time or just during a WOT run?
If you are just rich at WOT, then your PE tables need to be adjusted.
I don't know how much of a POS your laptop really is, but Datamaster does not require a lot of CPU overhead to log what you need. It will run on a 90 MHZ laptop with 32mb ram. You can also use their program in demo mode for
20 sessions before you have to buy it.
If you are just rich at WOT, then your PE tables need to be adjusted.
I don't know how much of a POS your laptop really is, but Datamaster does not require a lot of CPU overhead to log what you need. It will run on a 90 MHZ laptop with 32mb ram. You can also use their program in demo mode for
20 sessions before you have to buy it.
