Fluctuating Idle
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Joined: Apr 2001
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From: Lenoir City TN
Fluctuating Idle
I've looked at alot of archives but wanted to ask this question. I have an L98 with Lingenfelter 74211 cam, 350, super ram, hookers, AFR 195 heads. I've been chasing the idle fluctuations. The question is there possible something in the ECM that bases any control around the factory normal temp operation that is not adjustable in the BIN?
I feel I eliminated a vacumn leak. I used water and other means including disconnecting all the vacumn hoses from the engine other that the FPR. I was data/emulating hunting the problem and all of a sudden after I had the car idleing for a while is started idleing correctly. The MAP jumped up 10 and it was perfect. It was not anything I did. I flashed my chip for the changes I made, which were in the lower VE for idle, but when I put it back together it was some better but not like it was for that moment.
I have a 170 degree thermostat and am wondering if when the car reached into the 180's that something got triggered in the ECM?
I feel I eliminated a vacumn leak. I used water and other means including disconnecting all the vacumn hoses from the engine other that the FPR. I was data/emulating hunting the problem and all of a sudden after I had the car idleing for a while is started idleing correctly. The MAP jumped up 10 and it was perfect. It was not anything I did. I flashed my chip for the changes I made, which were in the lower VE for idle, but when I put it back together it was some better but not like it was for that moment.
I have a 170 degree thermostat and am wondering if when the car reached into the 180's that something got triggered in the ECM?
Safety Car
Joined: Sep 2001
Posts: 4,149
Likes: 551
From: Glenbeulah Wi
Superram's are hard to tune for stable idle the large plenium volume can cause a surge. What you need to do is make sure your idle timing is stable, make sure your fuel corrections are small at idle, makes sure the IAC idle position is around 20, play with the IAC steps per second response time to either speed up or slow down the IAC response to help keep the idle stable. You can also play with the deadband errors to not allow it to respond to minor changes so quickly. (Note I set idle timing at 20 degrees across the board to make sure the timing is stable, this has a huge effect on idle stability)
Racer
Joined: Aug 2009
Posts: 337
Likes: 6
From: Kanata ON
My idle is pretty good now but my fuel system and tune are far from stock due to running ethanol.
Two significant differences from stock are new (large) injectors and a WBO2 with narroband emulation for the PCM. The WB02 basically causes the PCM to always be closed loop. I mention that because one thing that can make you idle rough is a lean mixture. If you are running an original narrowband sensor that can be hard to judge because the non-heated sensors stop responding at idle. A WB02 is always a good investment IMO.
Two significant differences from stock are new (large) injectors and a WBO2 with narroband emulation for the PCM. The WB02 basically causes the PCM to always be closed loop. I mention that because one thing that can make you idle rough is a lean mixture. If you are running an original narrowband sensor that can be hard to judge because the non-heated sensors stop responding at idle. A WB02 is always a good investment IMO.
Thread Starter
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Joined: Apr 2001
Posts: 744
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From: Lenoir City TN
Superram's are hard to tune for stable idle the large plenium volume can cause a surge. What you need to do is make sure your idle timing is stable, make sure your fuel corrections are small at idle, makes sure the IAC idle position is around 20, play with the IAC steps per second response time to either speed up or slow down the IAC response to help keep the idle stable. You can also play with the deadband errors to not allow it to respond to minor changes so quickly. (Note I set idle timing at 20 degrees across the board to make sure the timing is stable, this has a huge effect on idle stability)
Safety Car
Joined: Sep 2001
Posts: 4,149
Likes: 551
From: Glenbeulah Wi
Thread Starter
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Joined: Apr 2001
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From: Lenoir City TN
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Thread Starter
Pro
Joined: Apr 2001
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From: Lenoir City TN
Superram's are hard to tune for stable idle the large plenium volume can cause a surge. What you need to do is make sure your idle timing is stable, make sure your fuel corrections are small at idle, makes sure the IAC idle position is around 20, play with the IAC steps per second response time to either speed up or slow down the IAC response to help keep the idle stable. You can also play with the deadband errors to not allow it to respond to minor changes so quickly. (Note I set idle timing at 20 degrees across the board to make sure the timing is stable, this has a huge effect on idle stability)
Where to I find the " IAC steps per second response time" and "deadband errors" in my BIN?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The IAC count is an indication of how much air is entering the engine. There is no "magic" number that it should be. The only thing you need to watch for is that it doesn't go down to zero. If that happens then the ECM has lost control of the engine. I like it up around 40 to 50 myself.
Burning Brakes
Joined: May 2013
Posts: 768
Likes: 24
From: Valrico Florida
Just curious as to why people say you want it at 20-30 or 40-50 considering it can adjust from 0-255 to compensate.
My guess is the more air the IAC has to let in to maintain idle the more hunting occurs, does that sound right?
My guess is the more air the IAC has to let in to maintain idle the more hunting occurs, does that sound right?
Safety Car
Joined: Sep 2001
Posts: 4,149
Likes: 551
From: Glenbeulah Wi
The lower it is without hitting zero the farther it can open to maintain the correct idle when the engine is cold under a load like in gear at 30 degrees.
Burning Brakes
Joined: May 2013
Posts: 768
Likes: 24
From: Valrico Florida
How bad is your hunting? Mine bounces a little between 540/590-620 RPM but is never so drastic I think it is going to stall.
In my case I might just leave it be, when driving around town I never really even notice it.
In my case I might just leave it be, when driving around town I never really even notice it.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
I'd set closed TPS idle timing at 22 degrees to see if this smooths it out, and I like idle IAC counts between 40 to 60 myself. TPS in speed density is read upon startup, so adjustment is not required like a mass air car.
Cruising
Joined: Feb 2013
Posts: 13
Likes: 0
I've looked at alot of archives but wanted to ask this question. I have an L98 with Lingenfelter 74211 cam, 350, super ram, hookers, AFR 195 heads. I've been chasing the idle fluctuations. The question is there possible something in the ECM that bases any control around the factory normal temp operation that is not adjustable in the BIN?
I feel I eliminated a vacumn leak. I used water and other means including disconnecting all the vacumn hoses from the engine other that the FPR. I was data/emulating hunting the problem and all of a sudden after I had the car idleing for a while is started idleing correctly. The MAP jumped up 10 and it was perfect. It was not anything I did. I flashed my chip for the changes I made, which were in the lower VE for idle, but when I put it back together it was some better but not like it was for that moment.
I have a 170 degree thermostat and am wondering if when the car reached into the 180's that something got triggered in the ECM?
I feel I eliminated a vacumn leak. I used water and other means including disconnecting all the vacumn hoses from the engine other that the FPR. I was data/emulating hunting the problem and all of a sudden after I had the car idleing for a while is started idleing correctly. The MAP jumped up 10 and it was perfect. It was not anything I did. I flashed my chip for the changes I made, which were in the lower VE for idle, but when I put it back together it was some better but not like it was for that moment.
I have a 170 degree thermostat and am wondering if when the car reached into the 180's that something got triggered in the ECM?
then after the warm up period the ecm tuned to the fuel octane using the knock sensor and used that timing setting..perfect idle.
I don't like waiting but it does idle good.
but one garage said that my injectors weren't firing right, this before I replaced the knock sensor and I had a error message. But that was probably because they were not getting the correct firing signals.
Then another guy said it might be my idle air control at the front of the throttle body. a solenoid that control idle air. He said they have to be cleaned with solvent to workright.
Other than that Im looking for the thread to dissaemble and replace the led readout for MPH and Fuel. I bought the new poloriizzing film
and I need a heads up to do it...any suggestions?
Thread Starter
Pro
Joined: Apr 2001
Posts: 744
Likes: 13
From: Lenoir City TN
Superram's are hard to tune for stable idle the large plenium volume can cause a surge. What you need to do is make sure your idle timing is stable, make sure your fuel corrections are small at idle, makes sure the IAC idle position is around 20, play with the IAC steps per second response time to either speed up or slow down the IAC response to help keep the idle stable. You can also play with the deadband errors to not allow it to respond to minor changes so quickly. (Note I set idle timing at 20 degrees across the board to make sure the timing is stable, this has a huge effect on idle stability)