Maybe someone knows?
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Senior Member
Joined: Jun 2001
Posts: 205
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From: Rochester, MI, USA
Maybe someone knows?
Hello,
97 4.6 Ext.cab (see signature) with around 160,000 miles on it.
Recently I installed new alternator and belt and that's where it started.
It goes like this.
Warm engine neutral gear. Idling at around 700 rpm. I press accel pedal and it revs to 1500 rpms. Then it goes down to 900, stays (!) there for a half-second and then finally goes down to 700.
Before it just went down to 700.
If I move and break rpms go down to 750 then go up (!) to 900 and then go down to idle rpms.
Before I didn't have that incline (so to speak).
Does someone know what / why is that? Do I need to expect anything?
Thanks in advance, Alex
97 4.6 Ext.cab (see signature) with around 160,000 miles on it.
Recently I installed new alternator and belt and that's where it started.
It goes like this.
Warm engine neutral gear. Idling at around 700 rpm. I press accel pedal and it revs to 1500 rpms. Then it goes down to 900, stays (!) there for a half-second and then finally goes down to 700.
Before it just went down to 700.
If I move and break rpms go down to 750 then go up (!) to 900 and then go down to idle rpms.
Before I didn't have that incline (so to speak).
Does someone know what / why is that? Do I need to expect anything?
Thanks in advance, Alex
Senior Member
Joined: Jan 2003
Posts: 150
Likes: 1
Sounds like when you changed the alternator you had to disconnect the battery,, this wiped out the memory in the computer and it is having to relearn all its sensor points and idle control points.
My Mustang takes about 100 miles to relearn its idle control. The Expey and Lightning do it much quicker.
Give it a little time.
My Mustang takes about 100 miles to relearn its idle control. The Expey and Lightning do it much quicker.
Give it a little time.
Thread Starter
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Senior Member
Joined: Jun 2001
Posts: 205
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From: Rochester, MI, USA
Thanks,
I did already a 1000 miles so maybe it still learns
But it's a very good suggestion - I'll disconnect it again and see if it'll fix it
Anyone else, please?
Alex.
I did already a 1000 miles so maybe it still learns
But it's a very good suggestion - I'll disconnect it again and see if it'll fix it
Anyone else, please?
Alex.
Technical Article Contributor
Joined: Dec 1997
Posts: 9,417
Likes: 11
From: Windsor,Ontario,Canada
When you disconnect the battery you erase the Keep Alive Memory (KAM) of the Powertrain Control Module (PCM). The PCM stores the Idle Air Trim values in the KAM. The PCM must relearn the new values. It can take up to 15 minutes of idling for the relearn process. The engine needs to see idle in neutral A/C off, A/C on and idle in Drive A/C off, A/C on. After the relearn process the PCM continues to adapt to changes.
Regards
Jean Marc Chartier
Regards
Jean Marc Chartier
Thread Starter
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Senior Member
Joined: Jun 2001
Posts: 205
Likes: 0
From: Rochester, MI, USA
Hello,
OK, I reset the CPU.
It's better now - on neutral (if I press pedal and watch how it goes to idle rpms) instead of *incline* in rpms it's flat for a half second at around 900 and then goes down. When I drive and break it looks OK, as it was before.
Another thing I noticed. Rpms go up slightly when tranny shifts to a lower gear.
Is that normal? Do I need to be concerned?
Thanks in advance, Alex.
OK, I reset the CPU.
It's better now - on neutral (if I press pedal and watch how it goes to idle rpms) instead of *incline* in rpms it's flat for a half second at around 900 and then goes down. When I drive and break it looks OK, as it was before.
Another thing I noticed. Rpms go up slightly when tranny shifts to a lower gear.
Is that normal? Do I need to be concerned?
Thanks in advance, Alex.
