98 taurus 24vengine sputtering

I recently was aske dto look at my friends 98 24v dohc (3.0l) taurus as it had died and wouldn't start. I scanned the codes and saw misifres in 1,2 and 5 cyls. as well as a 0174 code (bank 2 lean condition). I noticed that the car had a dead battery when it was brought to me. I jumped the car and got it to start, but after about 1 minute it started to run really rough and then died. I could smell gas at this time, just an FYI, After jumping it again it started and did the same thing. Since it had a dead battery I decided to check the alternator ( pulled the pos. cable on batt.) and found out it is not working. I am going to replace this tomorrow, but was wondering if anyone knew if this could be causing the other issues the car is experiencing? I charged the battery and managed to get the car to run, not smooth per se, but run nonetheless. I noticed that when it is running and I hit the brake the car starts to idle rough...(this by the way was the original reason I agreed to look at it). The car is from georgia, if that has anything to do with it.
Any help or pointers to help me find the real issue is greatly appreciated.

Mileage would be nice to know? And does your scanner list the degrees of misfire?
Just off hand I would suspect the:
MAF Sensor
O2 Sensor
PCM
Dirty Airfilter

Also, does your scan tool have the datastream mode and allow you to watch the battery voltage and lean/rich state in real time?

If you are really having a lean condition and misfires, that would imply that the misfires are due to those cylinders not getting fuel.

If the alternator is not working and the battery voltage is low, the computer could be functioning in an unknown state, possibly not turning on injectors, or mucking up the injector duty cycle, etc.

I'd suggest fixing the alternator/battery issue first and then going from there.

Also, for future reference, I would suggest not using the method of removing the battery cable to determine if the alternator is working. The battery helps smooth out the noise from the alternator. That noise can wreak havoc on a modern computerized electrical system. The battery acts as a large capacitor to filter the rectified AC provided by the alternator. An alternator does not provide very clean DC power without a battery.

-Rod

I am going to start with the alternator and I will update my progress then. The scanner I have is just a loaner from AZ so it does only the basics. (Nothing other than the code read outs). Thanks for the help here, I will let you know. And as far as the mileage on this thing, around 160k.

G

I replaced the alternator in this thing and although the alternator tested good at AZ (as well as my own test showing ~14.2 volts) it appears as though it is not working. I say this for two reasons, 1- if the positive cable is removed from battery the car dies instantly. 2- When tested at AZ in the car it varied wildy from 10.11 to 6.9. the test machine showed that it started around 10 and steadily dropped to around 7 and briefly showed around 11 again when the motor was revving. I can say with certainty that the car runs fine when the battery has a full charge, but when the battery is low it does all kinds of crazy things. (Like ABS light comes on, then fuel light, door dinging, engine sputtering, things you would expect to happen if there was insufficient juice to run components).

So heres my question: What would cause a known good alternator to not to produce enough or any juice? I checked the mark on the tensioner and the belt is within the good range. I checked the 30 amp fuse in the power block, it is good. I also removed the 175 amp Mega fuse and it had continuity as well. ( I am assuming this is just like a normal fuse only huge).

HELP! what else can I check?
p.s. there are no codes in the ECU....

Have the battery load tested, or if it is more than 4 years old, you may consider just replacing it. It sounds like you have a weak battery, bad battery cables, loose battery cables, or dirty battery cables). If the car's computer/PCM sees lower than 10.5 Vdc (at least that's the number that jumps to mind, it may be more like 9.8, but certainly more than 7 Vdc), it will operate in an unknown state and would definitely explain the engine stalling with the alternator disconnected (which you know I don't recommend) and the goofy instrument cluster indications and dinging. I believe the PCM is what controls the regulator of the alternator, so if the PCM is seeing an insufficient voltage, it may not be providing the proper signal to the alternator either.

Does the instrument cluster battery light come on? If the alternator is not functioning, it should turn on the battery light. There is a battery sense line that should have battery voltage at all times, and it is protected by a fuse, but I'm not sure which one. This line tells the voltage regulator what the battery voltage is.

-Rod

Rod,
The battery light does not come on at all. And just to clarify, I am not disconnecting the alternator, I am merely removing the battery cable from the battery. (Which in theory should prove the alternator working as the car should continue to operate. Meaning the battery is only being used for starting... and some small electronic devices/lieghts etc.). I have just gone thru the cables, the fuses, etc. and found nothing loose or fraying/corroded.

I thought I would disconnect the alternator main cable going to the fuse block (the one that continues to the battery) while the car is running to see what voltage I get from the post of the alternator. This way I would eliminate any backfeed voltage coming from the battery. This should give me a good idea of the alternator health, correct?
Also, is the anyway to jump the voltage regulator as in the old days (A and F ) to force the alternator to produce at max? Something like grounding the A terminal or something?
Let me know what you think. Mean time I will look for another battery to eliminate that possibility

Thanks again for you help,
G

The battery is still used even while in the altenator picks up the bulk of the electrical load. The battery is used to filter surges and the PCM will stop the engine if the battery itself is not working or present.
Carry the battery itself to walmart or autozone and they will check it free of charge.

I have to agree. I think you're next step should be to have the battery load tested. It's free and you may solve your problem with a lot less work than it takes to remove wires from the alternator.

-Rod