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-   -   Bouncing idle after Alternator change (http://forum.e46fanatics.com/showthread.php?t=949243)

pilotnbr1 10-07-2012 10:32 PM

Bouncing idle after Alternator change
Well I had my battery light go on. Pulled up INPA and sure enough the system voltage was 11.25 volts. I went out and got an autozone alternator and put it it. Battery light went out and system voltage at 14 volts. Well I go to drive the car and now coming to stops frequently the idle dips too low then bounces back up to about 1000 rpm. It even occasionally stalls the engine. I thought maybe my MAF got dirty when I pulled the airbox to replace the alternator so I cleaned the MAF. Same problem. I then disconnected the MAF and very slight improvement.

I have not pulled codes.. I have looked around to see if I knocked a hose loose or dislodged any of the ducting from the MAF to the TB. Everything looks normal. It is either something I did when I did the work or something this new alternator did or is currently doing.

Anyone have a bad experience with an autozone alternator? To me it almost seems like the alternator is putting too much load on the engine causing it to bog down when the rpm is decreasing and then it does not catch itself.

When I get home I am going to look at the codes. I am also contemplating disconnecting the plug to the alternator and go for a short drive.... Suggestions?

Starless 10-08-2012 09:57 AM

YES, had the same problem with an Autozone alternator (Duralast). It's the alternator. I lived with it for a year. Bouncing idle and whining sound. I hated my car for that year. It finally died a year later, around 12-14k for me. Got a free replacement from autozone and got lucky this time. No bouncing idle, no whining. It's a hit or miss with Duralast Autozone alternators.

Starless 10-08-2012 10:02 AM

I have a thread on bimmerfest called "alternator thread" that describes my misfortunes with that Autozone alternator, look it up if interested.

richkopena 10-08-2012 10:07 AM

Please do a search on Autozone alternators. You will find numerous stories of early failures and weird, noisy operation. Of course, not every one is bad but the amount of issues makes buying one unwise.

Mine lasted 4 miles, returned it and got my original failed unit back to use as a core for a Bosch rebuild.

pilotnbr1 10-08-2012 03:57 PM

Thanks for the replies! Hopefully a swap will solve this one. I had done a forum search (several ways/times) but all of the problems I found were with voltage, charging, noise, and short life span. Nothing regarding the idle...

Starless 10-08-2012 06:29 PM

Oh, yeah, my idle was all over the place, very annoying...

pilotnbr1 10-29-2012 08:32 PM

Update for anyone still following this or for future readers. I called autozone and asked if they had a valeo in stock, which they said they did. So I pulled out the duralast reman and took it in. When I got to autozone it turned out the "valeo" was just a duralast gold. Basically a new duralast.. I was pissed. So I put that alternator in. Problem was marginally better.

I ended up going online and found a bosch. The best deal was amazon. So once again pulled alternator out and put the bosch in. Fingers crossed and two days of driving the car no longer has the bouncing idle. One thing about the bosch though- the bracket opening on the bottom of the alternator was 1 mm too small to fit around the mount. I had to take a grinder to the threaded nut attachment which was causing the problem and shaved the 1 mm. I double checked everything else prior to doing this to ensure I had the correct bosch unit. Was kind of strange.... But anyhow that problem is solved...

Oil pan gasket, guibo, and rear wheel bearings next.. Maybe a new thermostat too- been throwing an intermitant code for it being jammed open.. It will be a new car by the time im done...ughhhm and empty wallet...

richkopena 10-30-2012 12:28 PM

I find it amazing how bad the Duralast alternators are! Were you able to use the Duralast as a "core" when you bought the Bosch?

pilotnbr1 10-31-2012 12:28 PM

I turned in my original core for 110 credit to get the duralast reman. The duralast gold was 300 with no core credit, which will be returned for a full refund. The bosch bought off amazon was 215 with no core charge or credit . I wish I would have bought the Bosch to begin with but i needed an alternator immediately.
So to answer your question, no, but it didn't matter because amazon was so cheap...

Starless 10-31-2012 04:37 PM


Originally Posted by richkopena (Post 14858028)
I find it amazing how bad the Duralast alternators are!

Like I mentioned above, I'm on the 2nd duralast alternator and it's working flawlessly (It's been 8 months since the install). The first one died but was faulty from day one. So, I think it's a hit or miss. Of course it's better to get reman oem if you can be without a car for some time (most places will not stock oem, so you need to order one)

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