2011 Tahoe Problems...?

[cdorton16]

Hi guys I have checked this site many times however I have never posted. Firstly I will introduce myself my name is Cody I am from Wisconsin and I have a been having a little trouble with my...well I guess my ole ladies truck. I don't drive it much so I am not certain how long the problems have been going on but I feel the problems need to be addressed. I will apologize now for any lack of punctuation or any typos as I know some folks are really **** about it...

The vehicle I am having issues with is a 2011 Chev Tahoe LT 4x4 and it just hit 90,000 miles...like I said earlier I don't know how long the problems have been going on I'm not a mechanic I would just like some insight as what I can expect if I should bring it in. My woman loves it and tells me it drives fine but I can feel somethings not right so here goes my list...

I'll start with the two that trouble me the most

1.) When I start up the vehicle in the dark (and probably in the day too I'll have to check) and put it in drive when I tap the gas the lights will flicker for a couple seconds and I can even feel a slight pulse coming from the adjustable pedals...I don't know if this is a surge or what nothing turns off completely. If I put it in park at any time and back into drive it will not do it - it's only the first time hitting the gas after turning the key and it does not do it in reverse only drive.

2.) When I turned the car on I noticed the voltage gauge was on the high side so I took it to advance as they're the closest to me and had a battery and alternator test done...The test came back the battery was good however the alternator was putting out too high of voltage (15.3v) I was curious so I took it home and pulled the alternator and the battery and brought them in for out of vehicle testing in which they both tested perfectly.(12.9 Bat) (14.4 Alt) I shrugged it off reinstalled them. Two days later I was running errands and I noticed the voltage gauge was reading a hair over 11 volts. I ran it home and threw a multi-meter on it and confirmed the 11 volt reading then I went back to advance and re ran the test with the same results - high voltage, however this time it came up my battery needed charging...I took it over to autozone for a secondary test and they couldn't even do it because my battery wasn't charged enough...as a precaution I replaced the alternator, the battery, and the 175amp fuse, however nothing has changed...


3.) When the vehicle is turned off it makes a weird "duhh" noise from the engine as though it is forced to stop faster than it should...it doesn't sound right and might be related to something else I don't know.


4.) I changed the running lights over a dozen times before I finally told her they were staying out. I don't know why they keep burning up but upward to 12 bulb replacements in 2 years is just not right. Especially when they make it such a chore to change. I have changed the headlight bulbs 3 times in 2 years if I recall correctly which does not seem right either.


5.) V8 to V4 mode is terrible if I didn't know any better I would guess the transmission was failing however it does not slip it just lags really bad when you're slow driving it you give it a nice push it goes good and you don't notice a thing just seems sluggish and it's being reflected in the mpg's


I really don't know what to do if any of you have any idea as of to what is going on and can point me in the direction of a fix I will definitely buy you a cup of coffee or a pack of smokes or something I don't know as much about this thing as I should.
I have been reading about a lot of people having issues with their BCMs and I was wondering if any of this sounds like a symptom I look forward to hearing from you guys I apologize if any of this is hard to read or if it's in the wrong spot for a thread


Maintenance done: plugs, wires, 175amp fuse, atlternator, battery

Thank you, Cody

 

[lamerem]

I can address a few of your questions:

1. The operating range of an automobile alternator is (13.3v - 15.5v). So while you are on the upper end of the spectrum you certainly aren't out of order. The standard alternator puts out high, and can only be fully tested under total load. ie. blower on high, headlights, high beams, hazards, wipers, stereo, etc.... I assume he did all of this? Also, an alternator will almost always pass a "bench" test as most bench testers do not load up the alternator.

2. The flicker could be the engine transferring to 8 cylinders from idle.

3. The "duh" sound is back pressure on the engine, may be something to have looked at.

4. Headlights and other lights. Be sure to use Dielectric compound when changing your bulbs. This keeps the sockets cooler and contaminant free. You can't really over do it hear. I was told by an electrician one time, if it squeezes out from the connector when plugged in, you have enough.

5. With 90,000 miles I would seriously think about changing your spark plugs with OEM iridium plugs. Your rough transfer from V4 to V8 could be a bad plug or just a slow plug from wear and tear.

I see that you have done plugs! Where they the ACDELCO Iridiums? I am a stickler for using OEM parts in the engine compartment. The engines where designed to operate with certain parts that operate at certain temperatures or variables.

 

[jetmech]

PCM controls battery charging and will allow it to drop to around 12V, this is done to squeeze out more mpg. This usually happens during steady state driving, although I'm not really sure which parameters have to be met for the voltage drop/alternator off to occur. It sounds like you might be having some ground issues too. Inspect your battery cables for obvious defects, especially around the connection lugs