Engine charge for HV Battery not working properly.

Hi again! I posted in another forum earlier, but felt that this forum may be more applicable for discussion of my problem.

When stuck in traffic jams, and my 2004 Prius shows 2 bars on the HV battery charge, it attempts to start the engine to maintain the charge on the HV battery. What was happening was the engine would attempt to start and then it would immediately die. It would keep repeating this process, over and over again, and would not charge the HV battery. Once I started driving out of the traffic jam, the engine ran fine and it charged up the HV battery while I was moving down the road. After receiving advice on here about this issue, I decided to clean the throttle body. My charging problem did change due to me cleaning the throttle body. Instead of starting and immediately dying, over and over again, the engine no longer dies. It now revs up, and slows back down to idle over and over again when sitting still with 2 bars of charge. The display does not show any charging going on during this revving up and slowing down episode. I need some more hints as to what to check out. I am studying electrical diagrams of the vehicle, but I need a synopsis of which system starts the engine for HV charging, and which system keeps the engine revving at the same RPMs during charging while not in motion. The throttle body cleaning made my 257 K mile Prius run like a scared deer again. I just need to get her charging while sitting still again. Thanks for any assistance you can offer. Oh yea, 12 volt charging system is in the 14+ volt range and 12 volt battery with no load is around 12.2 volts.

 

Yes original 12v battery.

 

Thanks BP! Glad you found me over here. I used brand new dealer TB gasket. What method do you use to find vacuum leaks? When I was much younger and less experienced I would spray starting fluid around the suspected area and wait for engine to change when starting fluid was sucked into the leak. Very risky using starting fluid for me and the sensors on engine. I then started using WD40 and watching for change in engine. I have also used the choke method where you cutoff airflow down the throat and see if the problem gets better. With this Prius I am unsure which method would be best.

 

Bisco I was planning on it, but last resort after I have explored all options. Thanks for your input!

 

To me if I had a vacuum leak, the problem would be constant. When HV fully charged, engine stops running when at stop in Drive. It starts right up once I hit the normal MPH for the engine to take over.

 

BP it surges when I am stopped in Drive with 2 bars of HV charge. It also surges in Park with 2 bars of charge. The display does not show arrows coming from engine to HV battery.

 

Throttle body has been cleaned. Gears are lubed. TB opens and closes by hand smoothly. Will try vaccum leak test in a sec. Thanks yet again!

 

OK here is my observation.

Started Prius just now with engine cold (ambient temp here in Ohio is around 70 F today. Sprayed starting fluid around TB, but no vacuum leak detected. With transmission in park, engine started fine and warmed up for around 2 minutes then shut down. I then rampled up the temperature on the climate control to force an engine start. That worked just fine. When I ramped the climate control temp back down, engine stopped at normal point.

 

Everything appears normal from cold start. Next observation will be to drive it for 15 minutes, turn it off, and start it again to observe functions at normal operating temps with HV fully charged.

 

OK I am back. With engine warm, and HV fully charged in the green, I turned off the car and restarted it. The engine started like normal, but this time when it should have shut off, it started surging up and down. I then put it in Drive and the engine stopped immediately. I then shut the car off again and restarted. The surging started agin where the negine should have been stopping. This time I place it in Neutral. The engine then revved up for a 5 second burst, and slowed back down to idle. It never did stop on its own in Neutral. When I switched from Neutral to Drive the engine stopped.