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Discussion Starter · #1 · (Edited)
This can happen if you replace your PCM and fail to have the Crankshaft Position Variation Learn procedure performed. Without having this done, there's no way for the PCM to be synchronized to your engine's crankshaft position sensor, and the PCM has no way to command the exact amount of ignition timing it determines to be appropriate.

For 1998 through 2005 vehicles, you MUST perform the Crankshaft Variation Learn procedure if you physically install a new PCM, replace the crankshaft, camshaft, timing chain, crankshaft position sensor or balancer. For 1997 cars, just swap the Knock Modules and you're all set.

Now that you know you need it, how can you get it done? Just see the following thread:

http://www.3800pro.com/forum/showthread.php?t=3
 

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You need to get a case learn with the install of a new cam? I wasn't aware of this. :confused:
 

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Mr. INTENSE said:
This can happen if you replace your PCM and fail to have the Crankshaft Position Variation Learn procedure performed. Without having this done, there's no way for the PCM to be synchronized to your engine's crankshaft position sensor, and the PCM has no way to command the exact amount of ignition timing it determines to be appropriate.

For 1998 through 2005 vehicles, you MUST perform the Crankshaft Variation Learn procedure if you physically install a new PCM, replace the crankshaft, camshaft, timing chain, crankshaft position sensor or balancer. For 1997 cars, just swap the Knock Modules and you're all set.

Now that you know you need it, how can you get it done? Just see the following thread:

http://www.3800tech.com/forum/showthread.php?t=3

The thread does not work. Can you assist?
 

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I've never had it done after all of my mods....Is that bad?
 

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Don't feel bad, neither have I :confused: :) 3 Cams later :eek:
 

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I'm getting it done tommorrow. Hopefully I will notice the difference....Also....is there such a thing as resetting the pcm? I heard If you take off the negative battery terminal and press on the brake. It will relearn the TPS curve and a bunch of other stuff....is this true or BS?
 

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little known things that gain you big differences...

thanks for enlightening them Scott... hey this is easy i can replace all this myself... why doesn't your product work right???? :)
 

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CASE relearn is done......All I've noticed is that it doesn't hesitate as bed when I accelerate, and it doesn't have as rough an idle as it use to. Spark advance, when they had it hooked up to the snap-on scanner, jumped to 36* when they reved it up. When I got it scanned at the track I think the max we saw was around 22-24*. Might of been more....But I definitely noticed a difference after the CASE relearn. Only cost $26.00. :)

Next up HIGH FLOW CAT :cool:
 

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NickT'sGTP said:
CASE relearn is done......All I've noticed is that it doesn't hesitate as bed when I accelerate, and it doesn't have as rough an idle as it use to. Spark advance, when they had it hooked up to the snap-on scanner, jumped to 36* when they reved it up. When I got it scanned at the track I think the max we saw was around 22-24*. Might of been more....But I definitely noticed a difference after the CASE relearn. Only cost $26.00. :)

Next up HIGH FLOW CAT :cool:

I hope you're joking about seeing 36* of timing....

Wide open throttle timing should never exceed 20* on a non-intercooled GTP, and part throttle timing should rarely be too much over 30*

Fix that, or buh-bye engine
 

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Discussion Starter · #11 ·
Wide open throttle timing should never exceed 20* on a non-intercooled GTP,
All INTENSE PCM's are coded with completely stock WOT ignition timing tables, unless the customer requests otherwise. For most L67-powered cars, this is typically in the 15 to 17 degree range.

and part throttle timing should rarely be too much over 30*
We don't add any timing at all, unless the customer requests it, and even then we don't touch the idle, cruise, etc. timing tables. It's entirely possible to see 36 degrees or even more with a completely stock PCM when letting off the gas, but this doesn't hurt anything since there's no load.
 

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I wasn't trying to make any accusations against the PCM, I was simply saying that if the engine was seeing 36* of timing under what he described as "when they punched it" it sounds like that was under load, and was troublesome to me.
I was simply wanting more clarification as to when he was seeing what timing, to make sure there wasn't possibly something wrong.

MT
 

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knock retard

Thanks to your forum, I'm getting closer and closer to fully understanding
knock. I'm still wondering a few things. For example, since 2,3,or 4* of knock is normal and acceptable, at what point will the knock sensor turn on the check engine light? If my engine is getting into the dangerous range of knock, will the check engine light go on for sure? If the check engine light is not on, what symptoms will I see with excessive knock?
Also, my mechanic recently scanned my gran prix GT and said that everything was perfect with no signs of knock. However, later I realized that I forgot to ask him if he checked it at different rpm ranges and at WOT. Is that always necessary, and do you think that most qualified mechanics know to check it at various RPMs?
 

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do you think that most qualified mechanics know to check it at various RPMs?
No.

As far as I'm aware, KR itself will not set an SES light. My poor car has seen as much as 14* and the poor thing limped home after shattering a plug and piston. However, related symptoms such as shattered plug, misfiring and a blown piston (all casualties of high KR) will eventually give you a misfire warning. Knock is the enemy, Knock retard helps you not blow up your engine by retarding your timing so you won't prematurely detonate. Buy yourself a general car maintenace manual. Learn to tell the color of plugs and inspect them during periodic chekups. KR will feel like a loss in horsepower.
 

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I have a friend that is a very competent and knowledgeable mechanic. Unless they work on performance motors and are in the habit of doing that, they won't be aiming for things like scanning at all rpm ranges etc. Look at the typical work they are doing and that will give you an indication as to what they will typically do/look for when working on a car.

2-4 degrees of KR is nto good in my opinion. Any KR is bad, since KR is the pcm seeing knock and removing timing to cope with it.... knock is present. Work to get the car knock free and you will be able to use all the potential power it has to offer.
 

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supporting MODS

Thanks guys. This KR has me wondering which MOD to do next. So far I have for my Impala SS is the CAI, and CAT-back exhaust. I want the PCM and a slightly smaller pulley 3.6, but to avoid any KR do you think I should put on PEMs with a downpipe and High Flow CAT first? Or, just go with the pulley and PCM first, then if I have KR I can open up the exhaust more?
 

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Thanks guys. This KR has me wondering which MOD to do next. So far I have for my Impala SS is the CAI, and CAT-back exhaust. I want the PCM and a slightly smaller pulley 3.6, but to avoid any KR do you think I should put on PEMs with a downpipe and High Flow CAT first? Or, just go with the pulley and PCM first, then if I have KR I can open up the exhaust more?
This thread is a sticky related to Knock after PCM replacement. Please create a new thread as to not post unrelated information here. Your questions are more related to general tech.
SV
 

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I have a friend that is a very competent and knowledgeable mechanic. Unless they work on performance motors and are in the habit of doing that, they won't be aiming for things like scanning at all rpm ranges etc. Look at the typical work they are doing and that will give you an indication as to what they will typically do/look for when working on a car.

2-4 degrees of KR is nto good in my opinion. Any KR is bad, since KR is the pcm seeing knock and removing timing to cope with it.... knock is present. Work to get the car knock free and you will be able to use all the potential power it has to offer.
Being a newbie to KR this has been one of the most succinct and clarifying explanations I have read to date. Thank you for that input.
 

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I hope you're joking about seeing 36* of timing....

Wide open throttle timing should never exceed 20* on a non-intercooled GTP, and part throttle timing should rarely be too much over 30*

Fix that, or buh-bye engine
can someone explain this further ^ ?

I havent been tuning long and had seen posts about bringing timing way up at cruise rpm's for better economy and have been able to get as high as 50* part throttle in low cyl airmass areas where I cruise on my highway commute

if you arent seeing KR how does additional timing do damage ?
 
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