How quickly does the PCM adjust after rocker install? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-23-2007, 02:47 AM   #1
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Default How quickly does the PCM adjust after rocker install?

So I'll be updating another post detailing my 1.95 rocker install. In the meantime, I was wondering how long it takes the PCM to adjust to the change? Driving home after the install, the car really felt sluggish from idle to about 4500 RPM. One time when I gunned it, I could see black smoke in the headlights of the car behind me. The car felt like it needed some motivation.
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Old 04-23-2007, 03:11 AM   #2
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I've heard about 100miles for the pcm to adjust to new mods. Just drive like you normaly do and in due time all your power will be waiting for you

Ed
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Old 04-23-2007, 03:27 AM   #3
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1.95 rockers are a pretty sizeable change. Give the car a few days and a range of driving conditions. If possible, get some scan data to see how the PCM is reacting to the changes.
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Old 04-23-2007, 07:44 AM   #4
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Did you happen to look at fuel trims, O2'* or KR after you made the change? These may have been indicators as to what was happening.

1.95'*....that required a spring and retainer change correct?
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Old 04-23-2007, 08:46 AM   #5
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OBD1 will take about 100 miles for 1.8'*, OBD2 a bit less. I'd give the 1.95'* about that amount of time on OBD2, but like the other Bill said, watch that scantool while it comes to you. You can actually watch it learn.
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Old 04-23-2007, 10:56 AM   #6
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You could also disconnect the battery for 10 minutes to let the PCM reset. This might be a good option to let fuel trims, etc start from zero. No need to overcome the current adjustments.
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Old 04-23-2007, 11:00 AM   #7
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Probably the best way to go Tom..
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Old 04-23-2007, 11:28 AM   #8
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Great - Thanks all for the feedback. I did have the battery disconnected for two days while I was working on it, so it probably is starting from scratch. I might re-scan in a couple days to see how it is going. I was just getting worried because I heard usually it would learn after about 30 minutes of normal driving and it was using quite a bit more fuel than normal. I swapped the PCM to ZZP'* a few days ago and it seemed to run fine then, so pretty sure that is not it.
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Old 04-23-2007, 12:17 PM   #9
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Quote:
Originally Posted by 67Goat
Great - Thanks all for the feedback. I did have the battery disconnected for two days while I was working on it, so it probably is starting from scratch. I might re-scan in a couple days to see how it is going. I was just getting worried because I heard usually it would learn after about 30 minutes of normal driving and it was using quite a bit more fuel than normal. I swapped the PCM to ZZP'* a few days ago and it seemed to run fine then, so pretty sure that is not it.
1.95 rockers is a big change, and bigger changes do require longer fuel trim learn times.

You'll be bouncing alternately between overly lean / overly rich for awhile, so drive like a grandma for at least a few days to a week. ONLY AFTER a couple hundred miles and some definite improvements in the way the car runs should you even consider gunning it.

Do you have a scantool? If not, beg, borrow, or buy one, 'cause without it you'll be blind. As others have said, scan for KR and LTFT and STFT and O2. Also scan rpm, TP%, MAP, MAF, IAT and IPW.

Silly question perhaps, but did you tell zzp about your 1.95 rockers when you ordered the PCM? (In other words, is that PCM tuned to the rockers?)
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Old 04-23-2007, 12:25 PM   #10
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what are we looking for when you say to check MAP MAF and IPW can i check these whit my aeroforce i know i have maf sensor and map frequency but dont know what is the normal reading .i do know about KR and IAT thank you
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