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Discussion Starter #1
I just got my mr2 back up and running finally after 6 months of sitting. It started up fine (with a jump of course). The alternator that I put into it works great so I know it is not that. The battery is pretty much dead...the whole time I had the car running (20-30 minutes) it charged it only enough to keep interior lights on for a few minutes. The problem I am having is that while it was running it was bogging down, I would let off the gas and the rpm gauge would drop to about 400 the lights would dim and the orange water faucet looking light would come one. It woud then proceed to work fine as soon as I pressed the gas pedal. I think it might be just cause the battery is dead but I am wondering if there might be more to the problem. It has an aftermarket radio in it with an amp running off the battery. Everything else is stock.

anyhelp would be appreciated
matt
 

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How do you know that "the alternator works great"? What are your voltage readings on the battery with the car off? how about on and running?

Off should read about 12.6V and on and charging will read in the neighborhood of 14.4V.

How old is the battery?

In case you don't have a multi-meter, they can be purchased at harbor Frieght for $3.99.
 

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Discussion Starter #4
I just got the alternator, it was checked out at autozone before i installed it. The belts going to the alternator is tight... There is a winding sound when I first start the car but goes away after a while, but I think that is the AC compressor though. Battery is a year old and still under warrenty.

Where are all the grounds for the engine at?
 

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Grounding points:
http://www.pbase.com/aw11mr2/image/37789802
As WIWhite87 said, buy a multimeter and chack the voltage when the engine is running.
You can also adjust the idle screw to increase the idle speed to around 850 rpms.
 

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Discussion Starter #6
I will try to get ahold of a multimeter tomorrow and test voltage. I will also check all the grounding spots for connectivity. The idle screw doesn't change the rpms...so I don't know if that might be a problem. Could a leak cause this kind of problem? I am going to get another battery tomorrow...I will update then on what happens.
 

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Shadetree mechanic
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Other things that can affect your idle speed are:
clogged air cleaner
timing is off
gummed up/dirty throttle body
http://www.pbase.com/aw11mr2/image/40005049
air leak between the intake manifold and afm
bad spark plug/plug wires/distributor cap/rotor (usually causing an irratic idle)

Also check the wiring between the alternator and the battery.
http://www.pbase.com/aw11mr2/image/36645457
In the picture, there are only a few strands of the white wire still connected to the the circular connector. Vibration and corrosion of the wire over the years increased the electrical resistance and limited the flow of current to the battery.
 

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Discussion Starter #8
not so sure about timing problem...since the idle is pretty stable. It only acts up when I let off the gas pedal, thats when the idle rpm dips. It's weird it worked fine before the alternator went out...but it was sitting for 6 months without being started.
 

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Don't assume that with a 1 year old battery that it's Ok. If they go dead, they can be damaged permanently. You may want to charge it up fully with a battery charger and take a voltage reading. If you have a dead cell, it'll show less than 12.X volts. Just because it's a new alternator and Autozone said it's fine doesn't mean it's fine. People have reported that that the Autozone rebuilds are notoriously bad and people have had them test them as Ok even though they weren't up to par.

Check for a vacuum leak. That can be one reason for a low idle. You can search by using some flammable gas (unlit) around some of the hoses. If the idle surges, youv'e found a leak. Be careful!

With a mutimeter, you might consider checking the TPS as well (throttle position sensor).
 

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Discussion Starter #11
I know the battery is pretty much dead. my mr2 wouldn't start after I turned it off after running it for 30 minutes or so. The alternator ran the car fine but didnt charge the battery at all. I am in maine so it gets really cold here and the fact that it has been sitting since july/august it seem logical that the battery would be shot. I hate to admit it but I have a cheap battery and it always fails under warranty. This is the third battery in three years...mostly due to alternators dying on me. So i am going to swap it in for a new one tomorow and go from there...i will definately try the leak test since i hear some air from left side of engine.

Also another thing, the timing belt was changed 8 months ago and timing and tps was set then. but. it doesnt hurt to double check them though.
 

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Try not to let the alternator charge a car from dead. It puts a lot of strain on it, and alternators aren't at their peak efficiency at idle anyhow. I've always been told to charge a battery with a battery charger unless you're stranded and have no other choice after a jump.

If you did the timing belt and TPS, the only thing I'd do is shine a timing light to confirm. You may also want to crank it so you can see if the exhaust cam is not a tooth off from the change. It's not uncommon to have it slip a tooth on a DOHC car when assembling, though I've never had a problem.

I also live in a cold climate--WI. I have left my car out when I was at college in northern WI for months at a time, not starting it for a couple weeks. It's seen temps consistently below -10?F for a week for a high. I've always had mine start even on a night it was -27?F. Then again, I try to never buy a cheap battery knowing I'll be in a cold climate where I want it to always start. I always opt to spend an extra $10 to get a battery with a "warranty" of around 6 or 7 years and I replace them after 5 full winters--cost, about $55 on sale at Farm & Fleet locally branded under their own name. My uncle works for Johnson Controls (Globe Union), so I tend to gravitate towards the ones that his company makes. None of us have ever had a failure with at least 20 batteries over the years in numerous vehicles.

Alternators fail. Finding a good one can be difficult. Right now I found a used one through a guy on the board that was an original Toyota one for around $30. They seem to last longest. Rebuilts never seem to go the distance. Besides, I could hardly go wrong for $30 taken out known to be working and spinning freely.

Edit: I agree with checking the grounds as well just to eliminate it as a cause.
 

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Discussion Starter #13
I wish I had a battery charger to charge it up...but i hooked it up to my wife's car for a good 15 minutes before trying to start it. It hung the first three times i started...starter seemed to be frozen. The battery I have in it is from florida...where it doesnt get cold. So the car went from florida to maine...big change in my opinion. The alternator i got in it now came from a board member and it is a toyota original so I am pretty confident in it.

When I found out the alternator was bad, the bolt that holds it onto the engine block was gone and it tore the insides of of the alternator up. The bolt came out somewhere between florida and maine...
 

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will the car stall out if u dont give it gas? on my car air was gettin into the throttle after the AFM and it would jus stall out but i dont think that is the same promblem but doesnt hurt to check...
 

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Discussion Starter #16
no update as of now...the place i bought the battery from couldn't pull up my information for warranty services. :( I have to go tomorow to talk to manager to get a new battery. I checked the ground points, the one coming off the battery going to the transmission looks dirty maybe corroded. The ground coming off the block looks kinda shady...it was barely hanging on. Maybe I will try to get ahold of some wire and run new grounds to see if that helps.
 

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drop in the batt you will prob. be fine. The alt does not "charge" the batt it maintains it. The alt and batt must work together to keep the car running durring amp draw changes. At low RPM the alt out put is low, the car is counting on the batt to take up the slack in the system. At higher RPM alt out put is high to run the car and maintain the batt. A car's systems are designed to opperate at thier peek when the car is off idol they werent ment to idol for long, a batt in a police cruser dosnt last very long eventhough it is run every day. I have had cars at work that driving down the road and turn on the high beams and the car would shut off, due to a bad batt.
Make sure you have corroded free connections and good cables.
 

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Discussion Starter #18
Update: Dropped the battery in today...it starts up alot better...still a little boggy but that could be cause by old fuel. I discovered that the brake fluid was almost all gone...about hit someone going to put air in the tires.. Well thanks for all the help.

matt
 

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Toyotas from the '80 are notorious for the battery terminals corroding. Those red and green felt things help, also some battery grease on top of the terminals help. Most reman. alts. suck. Especially if you are running foglights, amped stereo, etc. I got one from HiLo Autoparts (now Oreilly) in 1991 with the lifetime warranty and have gone through about a dozen or so since then. I have a nice stack of receipts dating all the way back to the first one. My first MK1 was running aftermarket foglights, 3 amp stereo, and a 1000 amp battery and the alts. only lasted about a year. The batteries only about 14 months.
 

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Discussion Starter #20
I am running an amp through mine...is it possible to run two batteries in a car? One for the car and one for other stuff??
 
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