Hey fellow Hybrid owners just wanted to run some thoughts by you all.

Took our 2008 GMC Hybrid in to GM dealer for intermittent rough/lurchy low idle speeds, Hesitations on acceleration both under normal engine power and just coming out of Auto stop, RPM flare-ups while holding steady throttle position on flat roads the RPM jumps from 1500 RPM (40ish MPH) to sometimes either as low as 2200 and as high as 5000 RPM randomly. Also intermittently while going under 25 MPH or stopping at stoplights etc., it doesn't go into auto stop as often as it used to and it seems to take longer to go into Auto Stop, all the conditions above are really noticeable until Auto stop resumes normal.

Had the dealer perform a full diagnostics test on Hybrid battery using the computer system and it's saying the Hybrid battery is within normal specifications. I was hoping for actual spec numbers but didn't get any (if even possible?) as both the service writer and Tech had already went home before being able to pick it up.

So far (even though I cleaned the throttle body myself two weeks ago) we let them clean the TB and do an fuel rail/injector clean. Cleaning solution part number says they used MOC05451 fuel&comb. Must be one of these ?, http://www.ebay.com/sch/i.html?_odkw...er+gm&_sacat=0

The new battery isn't installed yet as they had the wrong size. The parts look up system from new calls for a 615 CCA but under warranty in late 2011 they found that a 770 CCA battery should now be used.

So far the problem remains, Would you think installing a new 12 volt battery will resolve a problem such as this? Any other ideas would be greatly appreciated.

Thanks.

 

Is the air inlet to the HV battery full of lint? Pet hair and "normal" dust bunny material will build up on the "Cheese Grater" looking air inlet.


Driver's side of the HV battery steel box. A hot battery will cause some of what you say.


Next a single bad cell can too. The HV battery computer has 5 temperature sensors and 20 volt meters in it.


ALL can be read by a skilled tech with dealer scan tool.


If under a light to moderate HV load such as 10 mph flat level Electric, the difference from highest voltage to lowest voltage is much more than 0.75V, a cell is getting weak. Over 1.0V and there will be performance issues.


S Keith who posts here often is very skilled in the Panasonic battery modules used. He may know of a non-dealer scan tool to get you the min-vs-max measured voltages under specific loads.

 

Thank you Hillbilly_Hybrid for the very helpful reply, very much appreciated.

I was able to talk to the service tech and I had him read your reply to see if he checked the things you mentioned. He mentioned that the computer says the Hybrid battery is reading 304 volts and all the cells seem to be in normal range and the temperature sensors didn't or don't show signs of getting to hot.

That mentioned, (Plus thanks to you for describing the actual area to look as I for some reason thought the area to keep clean/clear was the front area where your feet would rest) I did find 2 1/2 rows of the 3 to 4 rows of wire meshing on the left side (closes to door), the lower vent holes were covered with hair type substance while rear vents only had one piece of styrofoam type material but no hair. I showed the tech the hair and he didn't seem to think it was enough hair to cause a hot battery running problem.

Before I had a chance to clean the hair and install the new upgraded 760 CCA vs the smaller 615 CCA 12 volt battery that typically comes up (on the 08's at least) when they run the vin number for parts look-up, At one point in the heat of the day which was right near 100*, It ran the worst "I" have ever experienced but my wife is the main driver and she has experienced it while it's cooler both morning and evenings.

For me today, It ran pretty well in the morning hours with very slight hesitations intermittently but on the way home it stopped going into Auto Stop, then the rough idle started up. I parked it in the hotter garage than what was outside for an hour and when I put it in forward gear and gave it less then quarter throttle I was lurched forward as the SUV did a hard nose dive plus you could hear a hard clunking sound from what seemed like the transmission area each time mainly just do to the violent nature of the lurching.
Also while it was running rough, If I held what would be roughly a normal working 15 MPH slow speed roll, the engine RPM flare went up quickly to around 2000+ RPM but I was only at a slow roll of 3 MPH and not gaining speeds at higher RPM's.

After the day and the SUV temps cooled off some, I installed the new recommended 12v battery and cleaned the vents... While it wasn't running as bad as when it was hotter, the idle was still kind of rough, still a little lurchy and not going into auto stop.

If it don't go into Auto Stop, you just know it's not going to run right.

Without pulling the Hybrid battery box and testing each cell independently like I've recently seen videos online of Toyota Prius owners doing, Not so sure of where to go next. Maybe the copper buss bar connectors are becoming corroded?

http://1.bp.blogspot.com/-cHvU-HXikF...0/Bus+bars.jpg

Thanks again.

 

The scan tool can also testr the battery pack coolong fan. I forgot to add that part. The correlation of higher daytime temperature and NO Auto-Stop is still leading me to believe it is largely temperature.


The cells can be in "normal" range at rest and then diverge in voltage under load.


If the HV battery gets too hot or too cold NO Auto-Stop for you.


Weak cells act up most of the time and will not cause lack of Auto-Stop unless a code set.


If it's 100 F outside, you should hear that HV battery cooling fan running.


Now a "Hot Battery Cool Down" trick.


1) Set front and rear AC on Outside Air Maximum cool on the floor. Front and rear high blower on the floor.


2) Drive above 50 mph steady state light load for about 15 minutes.


The idea is to create a pool of cooler air on the floor in front of those horizontal air inlet slots under the second row seat.


The cooler air conditioned air on the floor, with NO recirculation, NO recirc, and faster vehicle speed creates a positive cabin pressure relative to the HV battery cooling duct outlet under the vehicle.


This will increase the air flow and the cooling of the HV battery.


If after 15 to 20 minutes of steady easy 50 mph plus driving it behaves much better...


It is a temperature and or cooling issue.

 

Can't thank you enough Hillbilly_Hybrid for all the guidance and I'd like to say that the service Tech at the dealer I'm using in Moreno Valley Ca is great to work with as well as he is even open minded to suggestions from online auto forums for additional thoughts from members such as you. I invited him to follow this topic so he maybe lurking.

Well today was averaging 107 degrees outside according to the mirror temp gauge and after experiencing yesterdays very violent lurching, hesitations, engine RPM flare-ups which did not affect actual vehicle speed at light to moderate throttle positions along with a transmission type clanking noise do to possibly catching a gear to all of a sudden go forward which seemed to have happen even worse for me (not my wife though) right after a hotter one hour garage heat soak from a previous heavy traffic drive plus still partially clogged air vents and older 12v battery, Thus far today in slightly hotter temperature range vs yesterday's, Having the new battery installed plus cleaned air vents I'm extremely hesitant to say due to past experiences of being a very temperamental, intermittently bad running conditions this vehicle can be at odd times, (though I thought otherwise yesterday) the symptoms may have subsided some as I was unable to detect any of the really bad conditions like I did before the changes were done.

Using my infrared temperature gun, the front inside of the vehicle reached as high as 124 degrees in the front and 119 at the front of the battery kick panel... Then using your tricks of the floor air, I was able to get the temp down to 88 degrees relatively quickly as you can watch the temp drop at the front battery box while especially at speed.
While I couldn't get it to run bad today, I'm still very skeptical right now as this vehicle is again very intermittently temperamental at odd times. The real test should be tomorrow as my wife is going to drive it again after not driving it for a week now due to all the latest severe symptoms it has been experiencing lately in a very noticeable fashion.

I'll keep you posted of how its going and thanks again for your guidance.

Oh just so there's an image available online of the battery box vents, if the image shows up below, here is 8 years of buildup which really isn't to bad being that my wife who drives it 90% of the time is a professional dog groomer.

https://mail.aol.com/webmail/getPart?uid=20800&partId=2&scope=STANDARD&saveAs=I MG_5327.JPG

 

Well so many of you guys out there have been having these issues I took the time to get the dust off an old Tech 2. I borrowed a 2008 Yukon and I'm running the fan as fast as I can right now.


As you have figured out low 12V and NO start. It still needs the 12V system to run all the stuff to control High Voltage.


Not too much over 110F inlet air the the HV battery will get it hot enough to envoke severe power limits. Any hybrid needs a balancing act of engine and electrical power to operate well. If the HV part is limited severely, there is no more balance.

 

Thank you for taking the time to borrow someone's Hybrid and running some tests to share with us/anyone following these topics concerning possible heat issues and vehicle lurching, etc. on light to moderate accelerations.

For those following along, In the following link below are of some self tests Hillbilly_Hybrid performed and shared his areas of concern of what to inspect for while using a scan tool system.
https://www.greenhybrid.com/forums/f...12/#post259907

Though I'm not completely sure what the ESS system is but between your quote below about commanding the fan speed and the special quiet features mentioned in an article on the GM Hybrid design features I ran across online as seen in the highlighted area below 'Sort of has me wondering if the command setting within the scan tool is just for testing purposes only or could the battery fan be possibly reset/reprogrammed to maybe help run the fan faster to help cool the battery better all of the time if desired by vehicle owner should they not mind the extra fan noise.
On another note, Day one of my wife driving it to work and back was successfully done without any running issues/complaints but being Saturday = less traffic.

 

ESS = Battery Pack. Service called the HV battery computer BECM

Unfortunately fan is not re-programable

 

I wanted to chime in. My 08 HyHoe was also showing the symptoms of your original post. I had no check engine lights or alerts. The dealer said the Hybrid battery was within tolerance. So i called a local reputable hybrid shop. He connected his computer with software for diagnosing hybrid systems via the OBD port to the Hoe. In his opinion GM has defined the operating tolerances to give the illusion of long battery life but sacrifices the drive quality the worst the battery gets.

I decided to replace all the cells with a new batch of current gen ones. He ran diagnostics on the cells that were in my Tahoe and they were all around .9Wh. New they are to report 6-7Wh per cell. So they were not bad per-say, just worn and through with their expected life.

So what does GM consider "Within Tolerance"? After installing the new pack, Its a whole new vehicle with no more hesitation or any of the annoying driving issues as before. In his opinion, GM programmed things so that no errors directly related to the battery pack efficiency are logged until who knows when, possibly until the pack is completely dead.

I paid 2200 for new cells and labor. I recommend it if you are driving an 08 as it will get worst. I am also having the shop modify the fan speed so as to provide more airflow to the batteries constantly. All the stupid jerks and hesitation went completely away.

 

Hi Dirtrunner21, so are you saying that because the 300v hybrid battery was at the end of it's useful life, the truck was lurching and hesitating?

I also have an 08 Yukon with 230km and have had the same problems as FunTimes. Reading through this and other forums, the battery did not appear to be the cause but it now seems like it is.

I have been driving around in M4 mode to prevent autostop from kicking in but the hesitation is now happening in M4 mode too, just not as bad.

I came across a price of $2000 U.S. for a brand new genuine GM battery. Is it difficult to replace or does it need to be done by the dealer?

Any help appreciated.