low idle and shaking fixed

[aki334]

I recently posted about searching for solution to fix engine shaking at stop lights especially when it is hot outside.

 

- suggestions were to replace battery - replaced it with 850 cca group 65 (with small fabrications) - that did not fix it

 

- installed "ULTRA GAUGE" (small screen that connects to OBD 2 plug) and reads all kinds of live data, reads codes, pending codes, deletes codes, alarms for high and low etc...) and noticed that every time when engine shakes it is because it was at 12V at idle at stop light and then when ac cooling fan kicks in it gets even worse.

 

- red some TSBs about this situation where Subaru was replacing alternators on foresters, so I decided to replace my alternator.

 

- replaced the alternator and no more shaking, engine is nice and smooth. The ultra gauge reads 14.25-14.33 V all the time. I never see voltage in 12V ranges.

 

- I need at last 3 people to confirm their voltages when engine is warmed up and is parked. All loads must be off, so lights are turned off with switch to "o", turn off you AC and fan, turn off your radio, connect voltage tester to your battery post and with engine running measure battery voltage. If you see 14.2V wait little it might drop to 12V. Please post here your findings.

Edited June 12, 2021 by aki334

[cb1232186]

Going to be following this one

[iyalla]

Yup^^

[Brisvegas]

- suggestions were to replace battery - replaced it with 850 cca group 65 (with small fabrications) - that did not fix it ...

- red some TSBs about this situation where Subaru was replacing alternators on foresters, so I decided to replace my alternator.

- replaced the alternator and no more shaking, engine is nice and smooth. The ultra gauge reads 14.25-14.33 V all the time. I never see voltage in 12V ranges.

 

For what it is worth .. Fully charged automotive batteries should measure at 12.6 volts or above.

 

When the engine is running, this measurement should be 13.7 to 14.7 volts.

 

If you don’t have a multimeter to tell you the voltage of your battery, you can do a test of your electrical system by starting the car and turning on the headlights. If they are dim, that indicates the lights are running off the battery and that little or no charge is being produced by the alternator. If the lights get brighter as you rev the engine, it means the alternator is producing some current, but may not be producing enough at idle to keep the battery properly charged. If the lights have normal brightness and don’t change intensity as the engine is revved, your charging system is probably functioning normally

[Painless]

My results... On the 2019 Legacy Sport (original Battery)

 

No Load = 12.27 - 12.17

A/C turned on = 14.22

[aki334]

My results... On the 2019 Legacy Sport (original Battery)

 

No Load = 12.27 - 12.17

A/C turned on = 14.22

 

 

 

 

This is exactly what I have been looking for. Thank you.

[aki334]

For what it is worth .. Fully charged automotive batteries should measure at 12.6 volts or above.

 

When the engine is running, this measurement should be 13.7 to 14.7 volts.

 

If you don’t have a multimeter to tell you the voltage of your battery, you can do a test of your electrical system by starting the car and turning on the headlights. If they are dim, that indicates the lights are running off the battery and that little or no charge is being produced by the alternator. If the lights get brighter as you rev the engine, it means the alternator is producing some current, but may not be producing enough at idle to keep the battery properly charged. If the lights have normal brightness and don’t change intensity as the engine is revved, your charging system is probably functioning normally

 

Alternators are very simple but not that simple as many of you think.

People think - Uh - battery is charging I see 14V. Yes, that is one of the things but here I will tell you couple things that can cause bad idle even if your alternator is charging battery.

 

- diodes can go bad and your alternator can be sending certain amounts of AC voltage. it will still charge battery and your meter at 20 dc V setting will show everything normal.

- charging current with no load or constant (same load) should be nice and even, not jumping up and down by 3-4 Amps every half second - it will still charge battery and will show you everything normal with your meter.

 

EMI from alternator- can case all kinds of confusion to nearby sensors and PCM and still be charging.

 

Thank you for the input.

[Painless]

My older Legacy results... 2016 Legacy Premium (O'Reilly Super Start Extreme Part# 34EXT Battery)

 

No Load = 12.37

A/C turned on = 14.46

Edited June 17, 2021 by Painless

[aki334]

Thank you all who posted voltage results.

 

- I just wanted to update you all

- After installing new aftermarket alternator idle is as smooth as it can be

- so I had the original alternator and some extra time and decided to take it apart

- I have cleaned the internals with electro wash and noticed that the two copper rings that brushes ride on were little dirty from brush dust that was stuck to copper rings.

-after reassembling and testing the original alternator works like new. Idle is nice and smooth. Since the old one is working now I can return the new one and save me some money.

 

So in short - clean the two copper rings that brushes ride on - you will have to insert paper clip from the back of alternator and push brushes in with "L" shaped 0-ring removal tool to hold brushes inside or you will not be able to reassemble alternator. Clean the heavy windings inside with high greet sand paper then electro wash. Clean the the brushes with electro wash. You will need 17mm Allen socket with impact to remove the pulley. Before you disassemble anything spin the pulley by hand to get the feel of how it should sound. You should not hear any scraping after reassembly.

This job is not hard but also is not for everyone, you have to be clean and patient. Mark one line across the alternator halves so you know how to reassemble everything in original location.

 

In the future if you need new alternator then get the original or good used one or if you are good try cleaning like I did. Aftermarket alternators do not cycle on and off like our original ones. They are constantly at 14.25V which can cause some MPG loss.

Edited June 21, 2021 by aki334

[ammcinnis]

- I just wanted to update you all

- After installing new aftermarket alternator idle is as smooth as it can be

Thanks for following up.

 

... the two copper rings that brushes ride on were little dirty from brush dust that was stuck to copper rings.

Slip-ring contamination is unusual.

 

Clean the heavy windings inside with high greet sand paper then electro wash.

Please explain. Sounds like that could abrade the thin insulation on the stator coils. Edited June 21, 2021 by ammcinnis

[aki334]

Thanks for following up.

 

Slip-ring contamination is unusual.

 

Please explain. Sounds like that could abrade the thin insulation on the stator coils.

 

 

Yes slip ring somehow had some black dust accumulated and stuck to it.

 

I have cleaned the stator with high grit sand paper (400-500 grit ) from inside it had some surface rust. The stator inside the center is iron and nothing can be damaged. If you open any of the newer alternators you will see what I am talking about. The rotator looked much better. Electro wash spray is is really important to get all the dirt and old dust out especially from the area where brushes are.

Edited June 22, 2021 by aki334

[Legacy20161657616313]

I have a shaking issue while at a stop in reverse and drive. The shake is completely random. Sometimes it shakes consistently and sometimes no shake at all. I tested my voltage while in gear and load and got different readings.

No shaking in drive/reverse

14.23 to 14.25

While there is a shake in drive/reverse

It would start around 14.23 and drop to 14.10 at the lowest but is fluctuating between 14.10 to 14.25.

 

I would have to check more to see if it drops lower but it's crazy hot outside.

I'm wondering if a new alternator would be a fix for me. The dealer already replaced the tensioner, torque converter and updated the transmission software. The last time it was there for a week and they said the tranny fluid was low and that was causing the shake.

[aki334]

I have a shaking issue while at a stop in reverse and drive. The shake is completely random. Sometimes it shakes consistently and sometimes no shake at all. I tested my voltage while in gear and load and got different readings.

No shaking in drive/reverse

14.23 to 14.25

While there is a shake in drive/reverse

It would start around 14.23 and drop to 14.10 at the lowest but is fluctuating between 14.10 to 14.25.

 

I would have to check more to see if it drops lower but it's crazy hot outside.

I'm wondering if a new alternator would be a fix for me. The dealer already replaced the tensioner, torque converter and updated the transmission software. The last time it was there for a week and they said the tranny fluid was low and that was causing the shake.

 

 

Subaru Legacy alternator is designed to work on and off.

 

We have confirmed that our alternators will charge when decelerating.

 

If you do not have any mayor loads ON it will be around 12.33 V

If you have some medium loads it will be around 13.45v

If you have high loads it will be around 14.22-14.35

 

so all this is normal and has nothing to do with shaking

 

alternator in my case had some surface rust on stator and dirty slip rings from brush dust that was glued on the slip rings.

 

What you can try for quick fix before going with alternator is cleaning maf/iat and map sensor with electro wash or maf cleaner. If you want to try new alternator I would suggest OEM alternator since aftermarket do not cycle on and off like OEM alternators and your voltage will always be 14.3V.

[Legacy20161657616313]

The voltage drop and shake go together. When there is no shake the voltage sticks between 14.23-14.25. When there is a shake the voltage will vary between 14.1-14.27 Even with no load the voltage reads between 14.23-14.25. I'll check again tomorrow to get more readings.

[Legacy20161657616313]

Checked the voltages this morning.

Before starting 12.45

On with no load 14.3

With ac/radio/lights on 14.28

There is a distinctive change in engine sound when turning the lights on and off. No shakes this morning but it does do it completely random. I'll clean the maf sensor once the wife gets back.