Voltage Drop

[PimpRanger]

HELP!!! I can't seem to source out why the volts keep dropping in my 2000 3.0 . I have changed the battery and the alternator, I cleaned the IAC valve. I have not been able to find why the volts drop at idle. When I start it in the morning the volts are reading 14.2 to 14.6. By the time I get to the next corner, when I come to a stop in drive, the volts drop off to about 12.8 or lower. If I turn on any accesories, it drops below 12v.
I am getting the numbers off the capacitor for my stereo, which has not been turned on since this began about a month ago. If anyone can give me any information to help solve this i would be most grateful. Thanks.

PimpRanger

 

[monsta]

Can you verify from another source? A multimeter perhaps? It'd be a good idea to rule out that the display you're looking at could be off. Doubtful but...

Does your idle speed drop as well?

 

[locovaca]

Slipping belt?

 

[TomB1269]

Battery terminals nice and clean? Clean grounds for the stereo system? Grounds, grounds, and more grounds. Also some drop is normal, and the A/C system running (Defroster, etc) will dump quite a load, and it will show stopped in drive at an idle. If you are not below 11 or 11.5 you should be fine, especially if the voltage returns back to 13 - 14 plus when driving.

 

[PimpRanger]

Hello Everyone,
First let me thank all of you who replied, I really appreciate the insight & advice. Let me reply as follows:
My buddy came over, he's an auto electrical specialist. He used a multimeter & verified the battery is good (it's brand new). He also checked the alternator(new rebuilt) it's also good. He advised it may also be a ground loose somewhere.That will take forever & a day to find. One suggestion I may follow is to change the negative battery cable entirely. As for the belt, it is in good shape. There are no cracks, it is strong, there is no perceptable slipping, no whining from the accesories on the drive belt. When I swapped the alt I checked it.
Here's another part of the mystery, before this happened, my volts stayed at 14 or more all the time! I mean ALL THE TIME. My stereo is comprised of slightly higher end components, and the amps are designed to allow the system to operate at around 14v. It always did before.
Today, after work, when I got in my truck it barely started, the volts were at about 12. I had to rev it up to make sure it wouldn't stall. Driving home, after a couple of blocks, it seemed to level out. I could turn up the radio and all was good. When applying the brake the volts dropped, not too much, and seemed to stay up, not 14 but not 11. At idle while in drive with the brake on, the volts would dip to 12.3-12.8
Lastly, I hooked up to a code reader & got the following:
P1504 Idle Air Control Circuit Fault
P1507-( can't remember )
P0174 - System too lean
P1151 - Lack of H02S1 switches lean
I know what too lean means, just not sure why it reads that. Now does this mean my IAC is shot? Could that be the culprit? Again I wish to thank everyone for their help
Regards,
PimpRanger

 

[Earl43P]

Stop chasing the voltage "problem". It's merely a symptom.

Your real problem appears to be low idle from running poorly. This may be a case where cleaning the IAC simply won't work and you need a new one. What happens if you disconnect the IAC connector and run loads? No difference is definitely a bad IAC.

The O2 sensor sounds like it's bad (not switching). Replacing it may clear up the whole shooting match.

Lean could be caused by a vacuum leak, but would get reported on both upstream O2's. Since only one is getting flagged, suspect it. Check the HEGO fuse(s) too.

 

[PimpRanger]

Voltage Drop Fixed!!!

Hello Everyone,

After much frustration and about $350.00 (new battery & rebuilt alt. + new IAC) the problem has been fixed. As per the expert advice from the members I changed the IAC valve & the problem is gone!
I neglected to mention the loud whistle I kept hearing as I had not really noticed it until after I consulted the forum members. Regardless, I followed the advice i got & found the following:

I removed the IAC & cleaned it, no change. After buying a new one $110.00 CDN-yes ouch!) before I installed it, I removed the gasket from the throttle body. I found a lot of wet black gunk filling the upper chamber, or the top hole closest to the throttle body. I then used a can of 'Air Intake System' cleaner from the parts store. I directed the spray nozzle directly into the hole & applied a couple of short bursts at a time, while rotating the nozzle a bit to get it in everywhere possible. I allowed time between as I did not want to soak the intake system. I tried to wait until it appeared dry & did it again. After a few tries, the inside was starting to appear silver again, woohoo! Metal! I then started the truck with the part off to suck in as much air as possible to clean it out. I then hit it again a couple of times & it was completely clean inside. I now put back the gasket, installed the new IAC, started the truck & BANG!!!!! 14.4 volts steady, ALL THE TIME! No more drops, steady idle, plenty of power for accessories!

I want to thank all the members who took their time to try & help. I couldn't have done it without you.
PimpRanger

 

[Pdxguy77]

MY 90 Ranger is doing the same thing. Couple Electrician friends of mine said to check my IAC as well. PRetty covered over by carbon buildup. I pulled mine off last night and started cleaning it out with Carb cleaner. Minor difference. normally my drop goes down to 12.4 volts and now after two cleanings its up to 13.2 under load. Might end up just buying a new one. Its only 60 bucks at O'Reillys here.