I just noticed that when my truck is running and I turn my headlights on, the idle drops quite a bit. Does this sound more like an alternator or a battery not putting out enough juice?
I know it could be both, so I was wondering what they do when they test alternators/batteries at auto zone, advance, whatever. Does the alternator have to be off the truck for a test?

 

sounds like the engine is bogging down? i would think more towards alternator because it sounds like it is trying to work too hard to keep up

 

I'm heading out right now to get them both tested.

 

I've got bigger problems. Was on my way and the bastard won't go over 45mph without bucking like crazy. Sounded like a backfire through the intake also. When in neutral I can't rev over 3K. Of course, no CEL again. I'm so sick of this thing.

 

Realized the 3k is probably the rev limiter. How about a cam synchronizer for the problem?

 

3k RPM in Neutral is the limit. So that's not a problem. And FWIW, when the battery and alternator went bad in my dads boxvan, it was jerking and stuttering really bad. Did you make it to Autozone to get them tested?

 

No, had to turn around. Getting a blizzard tomorrow, so hopefully I can get it checked at the shop up the road this week.

 

Sounds almost like a fubared cat converter. Had that problem once on an older Grand Am, very similar symtoms and was cherry red at operating temp.

 

Could be bad bearings in the alternator, any squealing coming from the belt? You need at least 9 -10 volts for the computer to do it's thing if your voltage drops below that your motor will start doing weird things like bucking and stalling with lose of power. I would definitely suspect the alternator. What voltage are you getting when the engine is off? When the engine is running? should be close to 12 volts off and 14.2-14.5 when engine is running. Also do a load test on the electrical system to see if the alternator is making the correct amps.

God luck!

 

how much dropping are you getting when headlights are engaged...a slight drop 100-(maybe)200 is ok but more than that and you have serious Amperage problems. In a ranger..and this is universal..if the alternator is 100% shot then the truck will run straight off battery and once it is out you have to power. <-- that may sound redundant but people still dont understand..not you OP youre good. I would get the alternator double tested at diff shops for confidence sake and amp that battery up to a bigger cell size. makes a world of difference

 

Thanks for the help guys. I will let you know what the test shows when I get it done. What would be a good size battery to get? Can't really afford a red top right now, so something a little cheaper.

 

Run to a farm and fleet and get a factory cca. I think they're on sale at the moment.

 

Alternator and battery checked out good. 14.4 under load. Took it out for another drive today and there were no problems. Got it up to 65 without anything. I just picked up a coil pack to throw in later tonight. Keeping my fingers crossed. The hood has been open more than closed lately, really sick of it.

 

No squealing or whining coming from it.

 

Edit

 

Put the coil in it today, took it for a drive and it did the no go over 45 again. Started leaning towards a possible trans. problem. But, when I pulled over and shut the truck off for a few seconds, then started it back up, it drove fine. I am going to swap out my autolite double plats for some motorcrafts to rule them out. Don't know where to go next. Fuel pressure? Fuel pump? Swap out the computer? I'm just going to have to break down and take it in I guess.

 

Wirelessly posted

I wouldn't completely trust the read outs from autozone while it is still installed on the truck. I recently thought my wifes car had a bad alternator, batt light on and lights dimming and very hot alt, so I took it there. Everything checked out fine. Drove it one more day and her lights died, wipers moved slow, air bag light, abs light and batt light came on. Changed the alt and all is well now.

 

Went to an actual shop, not autozone. I will never step foot it in that dump again.

 

a concept for all with this sort of problem to understand, the battery is only in use to start the truck, after that the alternator takes care of all the electrical.

 

from my understanding, the readings at auto parts stores only check to see whether the battery is fully charged or not. it doesnt test them under load, which is what u need to check.

 

Have you checked the postive cable on the Alternator? I have an 08 Fx4 and the wire was hot and it corroded. And I had it in the dealership twice and they said everything was fine until the third time they finally found it.

 

dose your voltage gauge work right? my friends blazer stopped charging al together and the alt and batter tested good and then found out that it was the gauge not reading since it doesn't charge until it reads twelve volts i would imagine that your problem could be a sign of the gauge going out, i'll ask my friend and see if he noticed anything like that before it went out.