dslreports logo
 
    All Forums Hot Topics Gallery
spc
uniqs
3

Jim Gurd
Premium Member
join:2000-07-08
Livonia, MI

Jim Gurd to Doctor Olds

Premium Member

to Doctor Olds

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

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.
theboz1419
join:2003-02-12
Puyallup, WA

theboz1419

Member

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.

Juggernaut
Irreverent or irrelevant?
Premium Member
join:2006-09-05
Kelowna, BC

Juggernaut

Premium Member

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.

Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium Member
join:2001-04-19
1970 442 W30

Doctor Olds to theboz1419

Premium Member

to theboz1419
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.



Vchat20
Landing is the REAL challenge
Premium Member
join:2003-09-16
Columbus, OH

Vchat20 to Juggernaut

Premium Member

to Juggernaut
said by Juggernaut:

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.

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.