Voltage way too high

[Skyl3r]

Hello,

I have a 2005 4.6L Limited Explorer. Mostly stock. Just K&N intake and magnaflow catback.

For the past year or so (I don't daily drive my explorer, so I haven't bothered fixing it), my explorer battery would die if I left it off. I had talked to some friends and they told me it was likely the alternator. More recently, I was driving to work and I went to wide open throttle for probably around 4 seconds. This caused my SES to come on, but the car seemed to still be driving fine, so I got it to work and parked it.

Later that day I got in my car again and started it up but it was misfiring super bad, so I read the diagnostic codes and it was saying P0355, P0356, P0357, P0358. This is Ignition Coil E, F, G and H. Sure enough, if I disconnect the coils the car does not change how it's running.

I was told bad power could cause this, so I metered my battery with the car running, and it was reading 17v. I heard that the voltage regulator is in the alternator and so I replaced the alternator. It's still reading 17v though. With the car off, the battery is reading 15v.

Any ideas what I can check?


Thanks!

 

[Joe in NY]

I would check your meter first. I had a meter that was reading 10 volts on a 13 volt battery. I tested the voltage of several different batteries, chargers, and the 120V wall outlet. Sure enough they all read low. Grabbed another meter and turns out everything was where it should be.

Opened up the old meter and found a small trim pot. Turned it back and forth to clean of the oxidation and back to good!

 

[Skyl3r]

I would check your meter first. I had a meter that was reading 10 volts on a 13 volt battery. I tested the voltage of several different batteries, chargers, and the 120V wall outlet. Sure enough they all read low. Grabbed another meter and turns out everything was where it should be.

Opened up the old meter and found a small trim pot. Turned it back and forth to clean of the oxidation and back to good!

Hah. You were correct. I metered a wall outlet and it was saying 150v. I'll see if I can get a known good multimeter to test with.

Now I just gotta figure out why half my coils aren't firing