Is voltage too high?

[seangolden1983]

Howdy I have an 06 Yukon XL 1500 4x4 and I have been trying to figure out a misfiring on all cylinders when the air conditioning is off when on they stop soooo yesterday I hooked up to battery to check voltage all is fine but when engine running if I turn air on to engage the coolant fans it acts normal but when I turn the air back off the voltage shoots up to 15.25 then the misfires start I dunno but could this be bad voltage regulator any ideas are welcome thanks.

 

[iamdub]

This is a strange one. But, being the ignition and injector firing is all computer-controlled, and computers can do weird things when voltages are too low or high, I'd say you may have an easy fix. The voltage regulator is built into the alternator, but it's controlled by the PCM. Let's hope the PCM isn't telling it the wrong thing and the problem is within the alternator. Swapping it is quick and easy, so I'd start there.

 

[01ssreda4]

15+v will **** your battery up. Sounds like your voltage regulator is on the fritz.

 

[seangolden1983]

Ya so I replaced it but still have another prob made a video

this noise is maybe the camshaft sensor in front of engine? I have heard of these making a chirp noise if that's not it then I'm afraid my engine is bout shot and I'm not getting a code for the sensor either but after new alternator still having same probs one guy said maybe dirty lifter so I did a motor flush then oil change with rislone engine treatment and rislone compression restore ran a little quieter but still radical RPM fluctuations etc at park/idle. More with air conditioning off. Most misfiring stops with AC on. I disabled and one of my children are as well was needing something bigger like this to make life a lil bit better for him and this is what I get...I went ahead and took a shot in the dark the dealer said drop it off up there and he's gonna have a guy check it out which honestly I think he and I are on about same skill level lol so most likely the same conclusion I'll let y'all know either way what happens could help someone else later on.

 

[iamdub]

So, after the alternator change, the voltage is still high?

I'm lost on that chirping, but my guesses would be loose spark plug, bad injector, bad lifter or spun bearing. Any metal in the oil? I'm wondering if the engine smooths out with the A/C on because the PCM raises the RPM to compensate for the extra load. Maybe you're running on 7 cylinders but the bump in idle is enough to make it less noticeable. Could try unplugging one injector at a time. Whichever one you unplug and doesn't make the engine idle worse is your dead cylinder. The EVAP code may or may not be related.

 

[rockola1971]

No way thats a spun bearing. Doesnt remotely sound like a bearing spun. Pull the serpentine belt and start it up and see if it goes away. If it does then its your power steering pump. What are you using to check your voltage at the battery when the engine is running? Your dash gauge is not calibrated and could be way off so I would not rely on that. Put a voltmeter on it.

 

[Rivieraracing]

I agree with Rockola1971, sounds like a belt slightly slipping almost like maybe some grease or something got onto a section of the belt. Does it go away when the headlights or any other electrical load is taken off of the system? Does it still make the noise after driving for a while and coming to a stop (battery fully chargered)? Just throwing ideas out there, sure doesn't sound like a motor going out in my opinion

 

[Rivieraracing]

Also, make sure the fan speed for your heater is all the way off so it keeps the AC compressor from kicking on, the compressor can make some noise when it is getting weak