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Discussion Starter #1
1st question: does the alternator have an effect on average gas mileage?
My car started to have an unusual hum which i've isolated to be coming from the alternator. since that hum started, i noticed my mileage went from and average of 26 mpg down to 20 mpg.

2nd question: The Toyota parts department told me that the 1990 2vz-fe came with 2 different alternators. A 70A and an 80A alternator. My question is, if i install and an 80A alternator into my car, will it have a negative affect on the car?
I'm not sure which alternator my car came with yet.


here's what i know about my alternator: it has a hum which Haynes says could be a bad bushing. What's left of the part number is -62012. based on that number the Toyota parts dept rep told me that's the 80A alternator. but, several web sources say that it's the 70A alternator o_O
The reason i'm asking, is b/c i want to get the alt either from an aftermarket store or directly from Denso cuz it'll be cheaper. Toyota's askin for ~$275-300 >.<
 

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I also had a 1990 2VZ-FE and I have to put a new alternator in it. My car was an LE, power everything, and it had the 70 amp in it. There wouldn't be a negative affect from puttin the 80 amp in. Everything should be fused and this it what will keep it safe. Unless you have a bunch of extra electronics on the car you shouldn't need it. Besides I tryed to fit the 80 amp in my car, and it didn't work. It was about the same size but I remember the 80 doesn't have the same indent as the 70 and it was hitting some thing on one of the mounting brackets.

I would get one from and auto parts store, I like advanced auto, if there is one near you. Get the life time and you won't have to worry about it again.

I never heard of a bad alternator affecting gas mileage, but it is possible. It would be an extra load on the engine.
 

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Remove the belt and with your hand see if the alternator pulley spins freely. It probably will. If that's the case, the gas mileage problem isn't with your alternator. I would leave the alternator alone until it shows some other sign of it really going. If you are concerned about it's output, you might want to reinstall the belt and check the output with a DVM or take the car to a parts store in your area that does on car testing of the charging system for free.

Then look for other sources for you decreased fuel mileage. A good place to start would be to check for any engine trouble codes. If nothing shows up there, next jack up each wheel seperately and check for a bit of brake drag. If nothing shows up with the brakes, I would next check the engine coolant temperature sensor with a DVM and the specs from any manual, for being out of spec. If you still don't find anything, I would change out the thermostat. The thermostat could be opening late or be stuck in the open position causing engine warmup to be delayed. This results in the car running a richer than normal mixture during this extended warmup period.

Mike
 

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Discussion Starter #6
here's another symptom of my car which is why i assume the alternator is about to go.

Driving down a steep hill, i shift to neutral and just coast [assuming lower RPM's = less gas used]; the last couple of times i did it, the power cut out and i had to restart the engine mid-coast.

also, the CEL would come on periodically for a few miles and disappear.

DVM test on battery reads 12.73V so battery isn't an issue.

haven't done DVM test on Alternator yet as both Haynes and Chiltons aren't very clear on how to do this.

I did take a stethoscope to the alternator and have isolated the hum to the alternator. Also, the first time i noticed the hum, when i opened the hood, i smelled a burning smell like burning electronics...

I'll drop by autozone in a few minutes to have my charging system tested.

and after reading several posts on the EGR, i have a feeling my sudden drop in mileage may be due to EGR.
 

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JUST RE ENGINEER IT
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a plugged up egr might make it ping and mpg might get better, not the other way around
 

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"also, the CEL would come on periodically for a few miles and disappear."


If that's the case, read the code(s). I will give you a starting point.

Mike
 

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Maybe you have a bad ground or power lead to something that is intermittently drawing a ton of current to function, which would cause the alternator to possibly hum even if the bearings are fine.
Just a thought, maybe you can use an ammeter while the humming goes on and see what is being drawn.
 

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Discussion Starter #10
JJJJJJ said:
VIN will tell you if it is 70A or 80A.

I paid $140 for a remanufactured Toyota/Denso alternator with 1 yr warranty from the dealer. (plus $30 core charge - which they refunded).

You will need a hammer or mallet and screwdriver/pile to push back the sliding washer sleeve or the new alternator will not fit into the old space.

if it's an OEM reman, shouldn't it fit? o_O
 

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ASE Master, now Realtor
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The alternator housing is a somewhat imprecise casting, and the part being moved is a bushing that makes up for this lack of precision. Many alternator mounting schemes use this type of bushing.
 

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I'm with Mike. Unless the alternator pulley is hard to turn it wouldn't have any effect on the gas milage. If your battery is maintaining a charge then the alternator is probably OK. The autozone check will be interesting.

If the engine died from lack of electricity while coasting (assuming a dead battery because the alternator wasn't charging it) you wouldn't be able to crank the engine midway down the hill because there wouldn't be any electricity left in the battery.

If I recall, a clogged IAC valve might account for the car dieing while coasting down a hill. It might also have a negative effect on your milage.

Next time you get a check engine light try to pull over. Don't stop the engine (so the CEL doesn't go off) and check your CEL codes.

Kep
 

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timebuilder said:
The alternator housing is a somewhat imprecise casting, and the part being moved is a bushing that makes up for this lack of precision. Many alternator mounting schemes use this type of bushing.

I had this problem years ago when replacing the alternator on an old 86 Camry I owned. The new alternator wouldn't fit down in to it's bracket. The bushing was out too far. It took me a while to figure out a solution. I found a hex bolt and matching hex nut just a bit smaller than the opening. I screwed the nut down on the bolt and then placed the assembly in the opening for the alternator in it's bracket. I used 2 wrenches to unscrew the nut from the bolt, forcing the bushing back far enough for the alternator to fit in it's bracket. I was very proud of myself after it worked.

Mike
 

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Mike Gerber said:
I had this problem years ago when replacing the alternator ... I found a hex bolt and matching hex nut just a bit smaller than the opening. I screwed the nut down on the bolt and then placed the assembly in the opening for the alternator in it's bracket. I used 2 wrenches to unscrew the nut from the bolt, forcing the bushing back far enough for the alternator to fit in it's bracket. I was very proud of myself after it worked.
I had that issue on my Celica... I used a hammer (yikes!) !!
 

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ASE Master, now Realtor
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A couple of gentle taps on the bushing are usually more than enough to move it, using a small hammer.
 

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timebuilder said:
A couple of gentle taps on the bushing are usually more than enough to move it, using a small hammer.

I was never able to get a hammer in there to tap it. There was just not enough room. I even tried turning the hammer sideways, but then there was still not enough room to get any leverage at all. Oh well, it worked out.

Mike
 

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Discussion Starter #17
ok, autozone couldn't successfully perform the test, so i took my car to Kragen.

according to their test equipment, my car isn't charging the battery, most likely due to a bad alternator. The interesting thing is...they never touched the alternator. o_O

I'm goin to figure out what the haynes manual is saying and test the alt myself.
 

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Discussion Starter #18
ok, i just did a CEL diagnostic test, and i have a codes 25, 26, and 71

that could be what's causing my huge gas mileage drop.

But, i'm still concerned about Kragen said about my charging system not charging the battery.
 

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timebuilder said:
You don't need to "touch" the alternator to test it.
+1

all you need for an alternator test is a multimeter connected to the battery and someone to start the car

also, according to my chilton's engine code manual these are your problems:

25: air/fuel mixture too LEAN
26: air/fuel mixture too RICH
71: EGR system malfunction

how you're getting a mixture that is simultaneously too lean AND too rich can be most probably blamed on a bad O2 sensor sending bad signals at different times. A bad EGR valve is a bad EGR valve...
 
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