My 2008 Prius (200,000 miles) is starting to feel like it's taking more effort to go up inclines. We just drove from Phoenix to Colorado Springs and I started to notice it most when we reached Vail, Colorado. My foot was on the floor and we barely maintained 55mph (gradual acceleration, I didn't try to punch it). At first I thought it was because that area just had a giant steep mountain, but I'm noticing my car making more engine noise at 45mph going up a moderate hill here in town. Could I be imagining this or is this a thing? It's the original battery pack. Other than the water pump and a belt replaced at 100,000 miles, I'm not aware of any other engine repairs (only owned it since 160,000 miles). Fuel economy is still in the mid-40s and I can't think of any other symptoms.
Yeah probably a sign of weakened HV battery. Keep the display on the battery SOC and see if it drains and fills quicker than it use to (another sign). Research grid charging and see if that's for you.
How new is your air filter? Most cars produce excess horsepower so if the air filter is restricting air flow you just make less peak horsepower that you almost never use anyway. A Prius is different the engine was probably producing all the horsepower it could going up those hills. A dirty air filter reduces airflow and that reduces how much electricity the motor can produce. 1 or 2 horsepower might make a difference.
Filters are the low hanging fruit. Only takes a few seconds to check that. 200,000 miles on the spark plugs? I'd look there next. They're about 80-85k miles overdue. While you're in there, clean the throttle body and MAF. Also, some injector cleaner in the gas tank is a cheap harmless thing to try.
It's a thing not your imagination. You are also on the original engine which is more likely the source of the problem. Get hold of Steve at Phoenix Hybrid Batteries. He can quickly diagnose your car.
It's definitely not the filter. It's practically new. I'm hitting the road again from CO to CA on Sunday to finish out the road trip. I'll keep an eye on the charge/discharge on the battery and see about cleaning the MAF and throttle body when I get to my in-laws. Can you recommend someone in the Sacramento area to check out the battery/spark plugs? We moved out of AZ and are bound for South Korea and taking the car with us. I still have three weeks before taking the car to the port if anything needs to be fixed/replaced.
Road trip complete. The 12v battery still tests good and the hybrid batteries seem to be charging/discharging well. The bulk of the trip was uphill so not much charging took place during the trip beyond the two purple bars. On a steady downhill the battery charged in about five minutes, and on the next uphill it drained in about the same amount of time. Today the battery also charged in the same amount of time with A/C off going through a couple stoplights in town. I took apart the MAF and sprayed it out. The screws had to be chiseled out to find them there was so much gunk covering them. One side of the bulb was transparent and the other had a gray coating. A couple sprays and it was also clear again. The air throttle was another story. That thing looked like a rifle after a thousand rounds had been put through it. The top half is squeaky clean and the bottom half as much as I could get it. The big metal cavity below the throttle housing has a coating of build up, but there's no way I'm getting to that. I also dumped a bottle of fuel injector cleaner into the tank. I put it all back together and started up. I never noticed this before, but when I revved the engine while in park and held the pedal steady, the engine noise wasn't steady. It went up and down slightly. Is this normal? I'm thinking about taking the car in to a local mechanic my in-laws trust to inspect/replace the spark plugs simply based on the mileage.
it is likely the HV battery... mine failed with similar symptoms... uphill it would require more from the engine because it was only taking partial charge. I purchased a reconditioned from Hybrid Battery Replacement and Repair - Best Hybrid Batteries w/3yr warranty (didn't look closely at that though
sometime around the middle of May and so far so good.. noticeable change in mpg from around 38 to 42 or so... I'd like to compare against a new battery but that's not gonna happen
Thats likely residue from the throttle body and MAF cleaning; the cleaners are often based on flammable liquids (Xylol etc) so when they get into the combustion chamber through the air intake, it'll rev your engine a little.
Thanks for the tips everyone. I have one more leg of my journey (driving down the length of CA) before the car gets shipped overseas for my new job. In addition to the MAF/throttle cleaning and new spark plugs, I got the oil changed today and switched to a "high mileage" oil. The shop said they didn't detect any leaks, but the oil was very low which is happening more often. This oil change was at 3500 miles. Fuel economy the last couple weeks has averaged in the low-mid 40s. I got the tires rotated and the shop informed me the rear struts are leaking which caused some feathering on my nearly new tires. I replaced the front struts and all four tires last summer. I haven't hit any hills since I got to CA and started this discussion, but I'll keep my eyes open when I drive down to LA this weekend.
