Even though I have about 300 bucks in the whole car, it's pissing me of because it's so unreliable.

I have had two brand new batteries in it since I got it the first week of Jan, and it will kill the battery after about 3 weeks. My car has the slight light dimming only at idle when in gear, but it's not bad enough where the batt would suffer from it (i can barely even notice it, and whenever I come to a stop I slip it in neutral to keep the rpm's up). I though the alternator was bad, but I started the car and took the battery out, and I drove around the parking lot for a while with everything electronic turned on running off of the alt, and the alternator is pumping out plenty of current.

Whenever I come out and find a dead battery, the car NEVER wants to start when a new one is immediately plugged in. It's like the car has a mind of its own, and is Very selective about which battery it will run with.

I came out last sunday, and my SECOND 3-week old battery was dead... so I jumped the car, and drove around for about 2 hours in hopes that it would charge. I get in the next morning, car starts up fine, and I drive my daily routine of about 3 miles. I come out the next day, and the battery is dead and the car won't fire when cranked. I pull a known good new-ish optima red top from my other car to start the lex so I could stick the dead batt in and charge it up, but the damn car won't even start with a good optima!!! It just cranks and cranks and cranks and cranks. I know it's getting voltage, because it cranks the motor at what sounds like light speed, but the damn car won't even hit once.

Are all lexuses this damn sensitive to voltage? There has to be some kind of slow and gradual short in my wiring, because i've NEVER had any kind of voltage problems in any of my older high end electronic-filled luxury imports (infiniti Q45, way more electric gadgets than my lex). I'm stuck trying to figure out if there is a bad module somewhere. This car is 100% DEAD even with a good battery even though it was running perfect before the battery dies.

When it has battery power and works, the thing runs Flawlessly and all of the electrical components work like they should. If my problem is just because this lexus is oversensitive to voltage, then I'm going to get rid of it because it's the most unreliable car I've ever owned! I've spent like 200 bucks on new batteries since new year's for a car that won't even run..

 

Yeah, uhh..... Ya can't do that with a Denso alt. It'll kill the voltage regulator. Since that was the start of your dead battery issues....... maybe ya might wanna replace that. Even if it was before you did that, you still have a regulator issue on the previous symptoms. "Works" doesn't cut it with a denso alt. Weak regulators and armatures drop the voltage at idle.

 

i had a similar problem about 2 months ago. kepts having to jumps start it every coupla days. i took the advice of others and it turned out my hire harness was chewed through from my front driver tire. the harness that runs throught the driver front wheel well. i dunno if your car is lowered but that was my problem. also maybe try and check the grounds...

 

I had same problem last year... mine was a small plastic came off under the pass. side seat... it was eating up the juice... i just disconnected it and i never have this problem again... u probably have somewhere eating up the batt.... could be the interior light (driver or pass. side)... I had that problem too... just took out the light bulbs... good luck...

 

Toobs, thanks I'll check that. The car has some kind of tuner suspension on it with stock wheels, and the front drivers tire rubs the fender liner over big bumps.

OLT, My trip around the parking lot sans battery wasn't long enough to harm an internally regulated alternator. I just got the car the first week of January, so for all I know the battery issue could have been with the car before I got it. When it was towed here, it didn't have a battery in it...

****There is no problem at all with my car charging, the problem I'm having is that something in the car will drain my battery when the car isn't running, and that after a battery drains and a new one goes in the car will crank but not start.

My car does the same thing as yours (from your thread I found about wanting to overdrive your alt. with a smaller pulley), the idle is really low so the only time I see any kind of electrical drain is at low idle when the car is in gear. Did you ever fix that problem with your car?

 

Yes I fixed it... I replaced the alt which had a failing REGULATOR. (and a weak armature)

 

Will a failing regulator drain battery power when the car isn't running?

 

What's the alt hooked to?

 

Well, a brand new optima red top won't even start the car now. It has no spark, but it's dumping in the fuel cause it smells coming out the exhaust.

I have had a few people tell me that '92 ecu's go bad, is there something i'm overlooking here? Both coils aren't firing at all when cranked.

 

Ecu could be messed up causing somthing to stay on, I would have the alt replaced/tested first. I had this same issue with my 240 and I searched high and low for the problem, never did find it.

 

I appreciate the advice, but I fail to see how a bad alternator or regulator will cause a no-spark/no-start condition with a brand new optima battery.

 

Could this be ECU related? I have been reading alot of threads on here about no-start problems being caused by the ecu.

The symptoms that the car has that make me think it could be an ECU are:
-engine would die on me while driving randomly when the rpm's would fall to idle while going around a corner slow
-engine has always has a reallll low idle.. about 500rpm stopped in drive, about 600-650rpm in park
-maybe there is some kind of gradual short in the ecu that is causing the battery drain?

 

It sounds like its probably the ecu. If you have a friend with an sc then have them bring there car over, pull it out and try it in yours see if its any better. The ecu could cause a battery issue by malfunctioning and allowing power to something constantly.

 

Well, I got a new ecu and it fires right up like nothing is ever wrong! bad ecu was the culprit..

 

I guess not, The new ECU fired right up the first few times but now the car is back to a random no-start condition. I can crank it for about 10 seconds, and it will just barely hit once after 10 seconds. After about Five 10-second cranks, the little hit is big enough to start the motor. I'm stumped.