Alternator bad? Mechanic says not so + vsc + check engine

[LexusofQueensJuherd]

Hey gang,

Very new here. Apologies if this is in the wrong area.

I just purchased an 08 is250 from an older gentleman for about 5k, with 137k miles on the dash. 
 

First went to autozone, and they told me my alternator had an issue, but my battery was at 100%.

Went to a mechanic couple days after, told me it was fine. 
 

Went back to autozone to double check. Same diagnosis (alternator going bad).

What compels me to change it; had an issue two nights ago where I had the car doors open installing seat covers. Kept the ac running (accessory mode) to air out a spray I used while adding the covers. Tried to start, electronics started flickering. Car barely gave me a chug. Closed all doors, left it alone overnight. Next day, started a bit sluggish but turned right on. Tried it again, then regular start. 
 

Play it safe and replace it? 
 

With VSC + Check engine:

Car has never given me issues driving. Lights went on, and still no issue. Could drive with no hiccups, over 60mph. 
 

Disconnected + reconnected battery, disappeared for a few days. Stress tested the vsc button, and could literally feel the difference in driving. It works perfectly fine, but light came on again and couldn’t use the vsc anymore. Disconnected battery again, vsc is working again. 
 

Maybe alternator is wigging out electronics?

Regardless, I’m looking to change spark plugs, serpentine belt, and potentially alternator. Going on a trip to PA with girlfriend, and want this car to be bulletproof.

 

Any recommendations/ feedback would be very much appreciated.

 

[Bykfixer]

At the part store they run a load test on the battery that mimics a big draw. If it holds up to a certain voltage it means the battery itself is not weakened yet. As the battery ages it will weaken as in not be able to supply a given amount of cold cranking amps. When its cold the oil thickens some thereby making the engine have to work harder to rotate. Hence the term "cold" cranking amps.

I'd say you should investigate why the check engine lamp is lighting up. It could be a sign of what is taking place to cause your car to struggle to crank over. The part store can often "read the code" and determine why the CEL is lighting. My gut tells me your voltage regulator in the alternator is hit and miss. A long time ago that was a little box on the fire wall or fender. These days they are inside of the alternator. It determines how much electricity goes to the engine to keep it running and to the battery to charge it. It only has to be off by a little to keep the engine running but not have extra to charge the battery.

Another issue could be a parasitic drain. An out of the ordinary draw on the battery when the car isn't running. In my 04 GS 300 for example the CD changer kept trying to change discs and the seat memory kept activating. Now I could not hear the disc changer nor was the seat memory moving the seat, but they were drawing on the system leading to a weak or dead battery if I didn't drive the car every day.

Yet another issue may be short trips don't allow the battery to charge enough. Example; start the car, drive to a store 10 minutes away, finish there, start car and drive 10 minutes to another store. Never giving the engine a good 30-45 minutes to charge the battery back up to the voltage used to start the car can also lead to the hard to crank or dead battery issue.

Hope you find it soon and it's a cheap and easy fix. 

[LexusofQueensJuherd]

8 hours ago, Bykfixer said:

At the part store they run a load test on the battery that mimics a big draw. If it holds up to a certain voltage it means the battery itself is not weakened yet. As the battery ages it will weaken as in not be able to supply a given amount of cold cranking amps. When its cold the oil thickens some thereby making the engine have to work harder to rotate. Hence the term "cold" cranking amps.

I'd say you should investigate why the check engine lamp is lighting up. It could be a sign of what is taking place to cause your car to struggle to crank over. The part store can often "read the code" and determine why the CEL is lighting. My gut tells me your voltage regulator in the alternator is hit and miss. A long time ago that was a little box on the fire wall or fender. These days they are inside of the alternator. It determines how much electricity goes to the engine to keep it running and to the battery to charge it. It only has to be off by a little to keep the engine running but not have extra to charge the battery.

Another issue could be a parasitic drain. An out of the ordinary draw on the battery when the car isn't running. In my 04 GS 300 for example the CD changer kept trying to change discs and the seat memory kept activating. Now I could not hear the disc changer nor was the seat memory moving the seat, but they were drawing on the system leading to a weak or dead battery if I didn't drive the car every day.

Yet another issue may be short trips don't allow the battery to charge enough. Example; start the car, drive to a store 10 minutes away, finish there, start car and drive 10 minutes to another store. Never giving the engine a good 30-45 minutes to charge the battery back up to the voltage used to start the car can also lead to the hard to crank or dead battery issue.

Hope you find it soon and it's a cheap and easy fix. 

Thank you so much! I got two codes, and autozone tested my alternator.

 

your gut was spot on. They told me the voltage regulator, verbatim. 
 

As for codes, I got:

 

P0420: Catalyst System Efficiency Below Threshold ( bank 1) 

c1201 engine control system malfunction 

 

For now, I’m going to get my !Removed! into the engine bay and change the spark plugs + alternator. 
 

Thank you so much for the kind words! Really hoping it’s cheap. I want my girlfriend to be as safe as possible on our 6 hour trip.

 

And of course, I love this damn car lol. It’s my second car, and I’d like to have it longterm- at least until we’re forced to drive iphones with wheels. 😄

 

To follow up:

 

- I wonder if my alternator is wigging out my vsc, which in turn triggers by the engine system  code?

 

- Also, would my alternator be causing the o2 sensor wig out in my cat? 

[LexusofQueensJuherd]

@Bykfixer 

 

MIKE! I HAVE SOME GREAT NEWS!!!

 

I was teaching my girlfriend to drive one night, and I literally noticed a hiccuped muffling noise coming from the bottom of the car. 

Did some research, came across a post in this forum I believe where someone had a similar noise, and found this video: 

 

 

So! I took it to a muffler shop, and lo and behold, exhaust leak! Literally paid 80 bucks to get it fixed, and noticed immediately how quiet the car got when I started it back up. Then took it for about an hour drive, and guess what?

 

NO. CHECK.ENGINE. LIGHT.

 

SO FAR!

 

MY GUY! I JUST SAVED MYSELF FLIPPING 1300 DOLLARS ON A CAT EXHAUST COMBO!

 

CAR IS RUNNING LIKE A DREAM!

THANK YOU SO SO MUCH FOR THE ADVICE! I literally meditated on your comment while scrolling through hours of videos and forum posts. 

Hoping the light doesn't come on, and the cats give me another 50-60k miles. 

 

Thank you again! Take care brother. I'll see you on the road!