Topic 'Re: Resetting ECM-ECU on old car - helpful?' in forum 'Automotive' - dslreports.com

Re: Resetting ECM-ECU on old car - helpful?

Thu, 18 Oct 2012 09:47:26 EDT

Vchat20 posted :

All a battery is used for is to start the car.

That's incorrect. A battery is also a power buffer, and used to supply a stable voltage, and current. Alternators fluctuate as demand from the battery is needed, or exceeded.

This. And with pretty much all cars since around ~2000 or so having a lot of engine functions electronically controlled, a weak battery and forcing these systems to rely more on the alternator can cause all kinds of issues. And for most vehicles if they sense a low battery voltage, they will adjust the alternator output accordingly to try and recover which can also exacerbate things.

As a personal anecdote, my mom's prior vehicle, a 2000 Durango, had some strange issues at one point especially concerning staying running after starting. It would crank and start fine with no struggle but after a second or so would outright die unless you kept the revs up and even then it would struggle some. Mind you this was with the 4.7L engine which was the first in the model to go to a distributorless ignition (ie: Coil-on-pack, driven directly by the ECU). Long story made short it was narrowed down to a combination of a weak battery and battery clamps deteriorated greatly (possibly causing the weak battery issue). After the clamps and battery were replaced, the problems completely vanished from that point forward.
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Re: Resetting ECM-ECU on old car - helpful?

Wed, 17 Oct 2012 22:58:43 EDT

Doctor Olds posted :

said by theboz1419:

In fact when I took my car in to get a new battery, the old 7 year old battery still was able to get a good reading on a battery tester, and was around 13.5 volts.

No 12V Automotive starting battery is 13.5 volts. That is the alternator output, not the battery. A 12 volt battery that is new or in good condition is 12.6 volts (2.1 volts per cell) when fully charged.

[att=1]
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Re: Resetting ECM-ECU on old car - helpful?

Wed, 17 Oct 2012 22:41:31 EDT

Juggernaut posted :

said by theboz1419:

All a battery is used for is to start the car.

That's incorrect. A battery is also a power buffer, and used to supply a stable voltage, and current. Alternators fluctuate as demand from the battery is needed, or exceeded.
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I'm not anti-social, I just don't like stupid people.

Re: Resetting ECM-ECU on old car - helpful?

Wed, 17 Oct 2012 22:31:54 EDT

theboz1419 posted : Yeah, im wondering too, how a weak battery would cause shifting issues while accellerating. All a battery is used for is to start the car. After the car is on the altenator takes over and the battery becomes a drain until its charged again.

In fact when I took my car in to get a new battery, the old 7 year old battery still was able to get a good reading on a battery tester, and was around 13.5 volts.

I had the accel. problem for 6+ months and since I had the battery replaced 3 weeks ago, no more accel. problems. The battery would not cause issues other then not starting the car or causing the car to stall while in idle if the battery was totally gone. The Alternator either works or it does not.

Re: Resetting ECM-ECU on old car - helpful?

Wed, 17 Oct 2012 13:40:51 EDT

Jim Gurd posted :

said by Doctor Olds:

Weak battery was the cause of your issues, not resetting anything.

Not sure I understand this. How does a weak battery affect how a transmission shifts? Once the engine is running, the alternator is powering the electrical system in the vehicle.

Re: Resetting ECM-ECU on old car - helpful?

Tue, 16 Oct 2012 13:34:16 EDT

shdesigns posted :

said by Doctor Olds:

Weak battery was the cause of your issues, not resetting anything.

Re: Resetting ECM-ECU on old car - helpful?

Tue, 16 Oct 2012 12:04:56 EDT

Doctor Olds posted :

said by theboz1419:

I but resetting has helped solve a shifting problem i had when shifting into 2nd and 3rd.

After I bought the car 8 months ago it started to have a problem of losing power when I shifted into 2nd and sometimes 3rd. The car would hesitate and jerk for a second and then it would resume accelerating normally. My mechanic thought it was maybe my clutch slipping or I thought maybe the trans was the problem,

A few weeks ago my cars battery died and after replacing the battery, the car is shifting like it should and is not hesitating and seems like it has more power then before.

So it has helped in my case.

Weak battery was the cause of your issues, not resetting anything.
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What�s the point of owning a supercar if you can�t scare yourself stupid from time to time?

Re: Resetting ECM-ECU on old car - helpful?

Tue, 16 Oct 2012 11:42:12 EDT

MooJohn posted : If it had anything to do with adaptive parameters, it will "adapt" its way back to where it was in time.

The computer never quits adjusting. Changes in one direction may be slower than the other when it comes to safety. For example, timing is removed in big chunks when knock is detected and it is added back very slowly. A reset after a bad tank of gas my speed this but the car will eventually reach the same state whether or not it is reset.
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Re: Resetting ECM-ECU on old car - helpful?

Tue, 16 Oct 2012 06:32:00 EDT

theboz1419 posted : I know my car is newer, 2006 Honda civic Ex, but resetting has helped solve a shifting problem i had when shifting into 2nd and 3rd.

After I bought the car 8 months ago it started to have a problem of losing power when I shifted into 2nd and sometimes 3rd. The car would hesitate and jerk for a second and then it would resume accelerating normally. My mechanic thought it was maybe my clutch slipping or I thought maybe the trans was the problem,

A few weeks ago my cars battery died and after replacing the battery, the car is shifting like it should and is not hesitating and seems like it has more power then before.

So it has helped in my case. But I think it would not help much on a older car.

Re: Resetting ECM-ECU on old car - helpful?

Mon, 15 Oct 2012 11:43:24 EDT

mattmag posted :

said by fartness:

It can change if the car is driven differently. If grandma drives slow and then gives the car to someone who is lead footed, the transmission for instance, might be set to grandma's tone, and not a lead foot.

Not so much the transmission really, but more so the fuel delivery curve. For the most part, ECM parameters are about engine emissions and settings that effect them rather than felt performance.

Re: Resetting ECM-ECU on old car - helpful?

Sun, 14 Oct 2012 21:44:20 EDT

fartness posted : It can change if the car is driven differently. If grandma drives slow and then gives the car to someone who is lead footed, the transmission for instance, might be set to grandma's tone, and not a lead foot.

Re: Resetting battery on old car - helpful?

Sat, 13 Oct 2012 23:34:23 EDT

anon posted : Having noted the posting history of the OP.....why am I thinking the vehicle in question is a 1970's era point ignition and carb fuel delivery vehicle ?

Re: Resetting ECM-ECU on old car - helpful?

Sat, 13 Oct 2012 09:54:43 EDT

Doctor Olds posted :

said by fartness:

Will an older car run more efficiently if the battery is reset so the engine has to re-learn some things?

No! Not at all. It will actually be less efficient until all maps relearn the idle speeds for various temps and various electrical loads.

Basics of engine management
»www.teglerizer.com/fi/bem/Basics···ment.htm

said by fartness:

My guess, which is why I'm asking, is that an older car might not be as efficient over time, so that's why I'm wondering.

Are you saying the stored/learned data deteriorates or goes bad with age and is no longer digital (1's and 0's). It doesn't. If there were a need for clearing the learned map data, there would be a push button or toggle on the vehicle with instructions in the Owner's Manual...

An older car will be looser and have less internal friction so if in a good condition otherwise and well-maintained it can be just as efficient as the day it was created.
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What�s the point of owning a supercar if you can�t scare yourself stupid from time to time?

Re: Resetting battery on old car - helpful?

Thu, 11 Oct 2012 19:01:40 EDT

alkizmo posted :

said by fartness:

is that an older car might not be as efficient over time, so that's why I'm wondering.

An older car will have vacuum/compression leaks, grime, and higher friction. That's what's really causing the loss of efficiency. The computer does its best to make things run as smoothly as possible based on the info it gets.

As others said, it won't help efficiency, but might help some "issues" temporarely caused by odd sensors or extreme vacuum leaks.

Re: Resetting battery on old car - helpful?

Wed, 10 Oct 2012 15:05:25 EDT

mattmag posted :

said by TheHarvester:

Efficiently? no.
Driving characteristics? Maybe

This is exactly correct.

The ECM will drop to a "default" set of parameters that control various functions, and have not gone through the "adaptive" process yet.

So efficiency drops, but driving performance *may* improve if the adaptive numbers are skewed.

Re: Resetting battery on old car - helpful?

Mon, 08 Oct 2012 23:39:23 EDT

TheHarvester posted : Efficiently? no.
Driving characteristics? Maybe
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Re: Resetting battery on old car - helpful?

Mon, 08 Oct 2012 22:43:37 EDT

Jackarino posted : Before i got rid of my 02 Jeep a few months ago, I would disconnect the negative cable from time to time to adjust the TPS, etc.

Re: Resetting battery on old car - helpful?

Mon, 08 Oct 2012 18:47:08 EDT

MooJohn posted : The engine computer is constantly adjusting short and long term trim values. The only thing "resetting" the ECU will do is make it start calculating again from whatever harcoded starting values is has. Within a few drives the values will all be right back where they were before the reset.

If it drives any better during the learning period it means that a particular sensor is giving it false information. Finding and fixing that is the key to a long-term fix.
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John M - Cranky network guy

Re: Resetting battery on old car - helpful?

Mon, 08 Oct 2012 14:36:55 EDT

Juggernaut posted : Most engine management systems relearn every time the vehicle is started because of air temps, engine temp etc.

Unless the vehicle has thrown a code that needs to be reset, it shouldn't make any difference for efficiency.
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Resetting battery on old car - helpful?

Mon, 08 Oct 2012 13:55:31 EDT

fartness posted : Will an older car run more efficiently if the battery is reset so the engine has to re-learn some things? My guess, which is why I'm asking, is that an older car might not be as efficient over time, so that's why I'm wondering.