? about resetting the PCM
09-30-2005, 09:50 PM
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? about resetting the PCM I searched the archives(for those who don't like to answer the same question twice) and still found no clear answer. When the PCM is reset, does it re-learn ignition timing as you drive? I put a lid on awhile back, and it now pings above 5500 rpm, so I'd like to know how to fix this issue. Thanks, y'all.
09-30-2005, 10:14 PM
#2
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kind of....
the PCM has 2 timing tables, high octane and low octane.... they're not binary (use one or the other) ... there's a "learn factor" or a weight value generated , the longer you drive w/out knock retard, the more that learn factor causes you to run on the high octane tables... if you get knock it learns more towards the low octane.
So after resetting your PCM it does have to learn to trust the high octane tables again.
If the engine's pinging , did it just start? Did your gas stations just recently switch to gasoline with Ethanol? The PCM should detect knock if audible pinging is present and automatically lower the timing, but if it's already all the way in the low octane and still pinging the problem lies elsewhere....
Would help if you could get a scan of the car to see if knock is being detected and see how much timing the PCM is requesting
the PCM has 2 timing tables, high octane and low octane.... they're not binary (use one or the other) ... there's a "learn factor" or a weight value generated , the longer you drive w/out knock retard, the more that learn factor causes you to run on the high octane tables... if you get knock it learns more towards the low octane.
So after resetting your PCM it does have to learn to trust the high octane tables again.
If the engine's pinging , did it just start? Did your gas stations just recently switch to gasoline with Ethanol? The PCM should detect knock if audible pinging is present and automatically lower the timing, but if it's already all the way in the low octane and still pinging the problem lies elsewhere....
Would help if you could get a scan of the car to see if knock is being detected and see how much timing the PCM is requesting
10-01-2005, 09:15 AM
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Mike, you ROCK!!! Thanks for the insight, bud.
I don't know that anyone's put ethanol into our gas yet(Georgia kinda slacked on gas additives this month due to Katrina). As far as when it started, I had no trouble at all with the stock lid, but when I put on the aftermarket lid and gunned it the first time, it made a ping/knock-type noise at WOT around 5500 rpm and up, and has done it ever since.
Now, the car doesn't see WOT all the time, so could it be leaning more toward the high-octane settings under normal driving for the entire operating range, or should it remember when and under what conditions to pull timing?
I don't know that anyone's put ethanol into our gas yet(Georgia kinda slacked on gas additives this month due to Katrina). As far as when it started, I had no trouble at all with the stock lid, but when I put on the aftermarket lid and gunned it the first time, it made a ping/knock-type noise at WOT around 5500 rpm and up, and has done it ever since.
Now, the car doesn't see WOT all the time, so could it be leaning more toward the high-octane settings under normal driving for the entire operating range, or should it remember when and under what conditions to pull timing?
10-01-2005, 09:27 AM
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Originally Posted by horist
kind of....
the PCM has 2 timing tables, high octane and low octane.... they're not binary (use one or the other) ... there's a "learn factor" or a weight value generated , the longer you drive w/out knock retard, the more that learn factor causes you to run on the high octane tables... if you get knock it learns more towards the low octane.
So after resetting your PCM it does have to learn to trust the high octane tables again.
If the engine's pinging , did it just start? Did your gas stations just recently switch to gasoline with Ethanol? The PCM should detect knock if audible pinging is present and automatically lower the timing, but if it's already all the way in the low octane and still pinging the problem lies elsewhere....
Would help if you could get a scan of the car to see if knock is being detected and see how much timing the PCM is requesting
the PCM has 2 timing tables, high octane and low octane.... they're not binary (use one or the other) ... there's a "learn factor" or a weight value generated , the longer you drive w/out knock retard, the more that learn factor causes you to run on the high octane tables... if you get knock it learns more towards the low octane.
So after resetting your PCM it does have to learn to trust the high octane tables again.
If the engine's pinging , did it just start? Did your gas stations just recently switch to gasoline with Ethanol? The PCM should detect knock if audible pinging is present and automatically lower the timing, but if it's already all the way in the low octane and still pinging the problem lies elsewhere....
Would help if you could get a scan of the car to see if knock is being detected and see how much timing the PCM is requesting
What effect does it have?
10-01-2005, 09:58 AM
#5
TECH Senior Member
^^^ Ethanol contains more oxygen than 100% gasoline ... so the 10% ethanol causes you to run a little leaner (~3% leaner or so). Because of this, cars that are on the brink of pinging can start to ping until the LTFTs level out and richen the mixture up (should't take long and no perm damage should occur... until recent I didn't realize that "corn gas" wasn't used throughout the country... I always assumed that everyone had ethonal in their gas heh)
Basically, it's a way of increasing volume but barely affecting mileage (10% more volume, 3% worse gas mileage) It's been used in the midwest for as long as I can remember, and I think w/the recent gas shortages they're pushing to use it throughout the country since it increases total volume and uses a product we have plenty of and can make plenty of ("corn gas")
Basically, it's a way of increasing volume but barely affecting mileage (10% more volume, 3% worse gas mileage) It's been used in the midwest for as long as I can remember, and I think w/the recent gas shortages they're pushing to use it throughout the country since it increases total volume and uses a product we have plenty of and can make plenty of ("corn gas")
10-01-2005, 10:00 AM
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Originally Posted by Ric
Mike, you ROCK!!! Thanks for the insight, bud.
I don't know that anyone's put ethanol into our gas yet(Georgia kinda slacked on gas additives this month due to Katrina). As far as when it started, I had no trouble at all with the stock lid, but when I put on the aftermarket lid and gunned it the first time, it made a ping/knock-type noise at WOT around 5500 rpm and up, and has done it ever since.
Now, the car doesn't see WOT all the time, so could it be leaning more toward the high-octane settings under normal driving for the entire operating range, or should it remember when and under what conditions to pull timing?
I don't know that anyone's put ethanol into our gas yet(Georgia kinda slacked on gas additives this month due to Katrina). As far as when it started, I had no trouble at all with the stock lid, but when I put on the aftermarket lid and gunned it the first time, it made a ping/knock-type noise at WOT around 5500 rpm and up, and has done it ever since.
Now, the car doesn't see WOT all the time, so could it be leaning more toward the high-octane settings under normal driving for the entire operating range, or should it remember when and under what conditions to pull timing?
10-01-2005, 10:12 AM
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Originally Posted by horist
^^^ Ethanol contains more oxygen than 100% gasoline ... so the 10% ethanol causes you to run a little leaner (~3% leaner or so). Because of this, cars that are on the brink of pinging can start to ping until the LTFTs level out and richen the mixture up (should't take long and no perm damage should occur... until recent I didn't realize that "corn gas" wasn't used throughout the country... I always assumed that everyone had ethonal in their gas heh)
Basically, it's a way of increasing volume but barely affecting mileage (10% more volume, 3% worse gas mileage) It's been used in the midwest for as long as I can remember, and I think w/the recent gas shortages they're pushing to use it throughout the country since it increases total volume and uses a product we have plenty of and can make plenty of ("corn gas")
Basically, it's a way of increasing volume but barely affecting mileage (10% more volume, 3% worse gas mileage) It's been used in the midwest for as long as I can remember, and I think w/the recent gas shortages they're pushing to use it throughout the country since it increases total volume and uses a product we have plenty of and can make plenty of ("corn gas")
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10-03-2005, 08:15 AM
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Nope, no MAF other'n the stock one.
And I wish like CRAZY that people would boycott oil altogether ad make the swap to ethanol... or at least E85... people here don't even know what that stuff is, nevermind they used to run it up the holler in their old big-block Dodge.
And I wish like CRAZY that people would boycott oil altogether ad make the swap to ethanol... or at least E85... people here don't even know what that stuff is, nevermind they used to run it up the holler in their old big-block Dodge.
