2004 Toyota Avalon 1MZ-FE V6 165,000 miles and recommended maintenance schedule observed.
A few times this Summer on really hot days of 95* fahrenheit and higher, my engine would have trouble accelerating with noticeable loss of power. But it was not frequently that this occurred. As the weather cooled back into the 80s recently it always ran fine and after changing the oil and filter at 165K last week using full synthetic it ran even better with that fresh oil and air filter. And I am thinking, wow the old girl still runs great! But then yesterday we had another hot day with a temperature of 95+ and again I experienced the engine 'bog' down, or not have normal power when trying to accelerate up to the highway speed of 70 mph. This morning when I drove it with temperatures in the 70s and 80s it ran fine. Note: on the hot days when it has run poorly, the AC was running, but on the other hot days when it ran fine, the AC was on also.
The check engine light has never come on in my 15 years of ownership. I thought perhaps it is a dirty fuel filter or clogged catalytic converter, but would air temperature affect those? Has new PCV valve and recently cleaned the MAF sensor. The timing belt and spark plugs were replace at 90K with OEM parts. Around 10K ago I cleaned the throttle body. That's about the limit of my expertise. 😉
So, what could be causing this sluggish behavior seemingly influenced by hot weather? By the way I live in southern California so humidity is usually low, if that matters.
Any thoughts or advice is much appreciated.
Warmer air is less dense, as a result, the engine feels out of breath when compared to driving on a cold/cool day.
It’s similar to when you drive at a higher altitude. The power loss is probably amplified in an 18 yr old engine.
Ofcourse, if you mean rough running or hesitation, then that’s a concern which you need to fix.
Thanks for your reply. Yeah, that's what it feels like, like it's out of breath as if someone stuffed a rag into the air intake. Or like trying to accelerate in too high of a gear. Maybe the four speed transmission is not downshifting properly.? But would higher temperatures affect the shifting of the transmission? It's not slipping. It doesn't hesitate or run rough. And again it does not always have this problem on hot days, just occasionally. Hopefully I can get it over to an AutoZone in the next day or two as @Doc mentioned to have it scanned for codes. Thanks @InThrustWeTrust
Another low hanging fruit would be a dirty engine air filter. Check it in broad daylight if you can see sunlight through it, when pointed at the sun. Ofcourse, if there are stored codes, they should point you in the right direction.
Thanks, but as I stated in my original post, I did change the air filter last week when I changed the oil and oil filter. I change it at least every 10k miles. But I appreciate your consideration and advice.
Oops, sorry. If you haven’t already changed the fuel filter, do so and pressure test the fuel pump.
I do need to have both of those services performed. Thanks.👍🏼
When was the transmission fluid and filter last changed? Has it ever been scanned for codes?
Sorry...I forgot to include that. The transmission fluid has been 'Dealership' serviced every 30K miles and was last changed at 150K. It shifts as smoothly now as when I purchased the car when it had 40k miles on it. And no, it has never been scanned for codes. I thought that it could only be checked for codes if the check engine light was on. But I will take to AutoZone and have it scanned and let you know. Thanks.
@Doc Had my car scanned at AutoZone this morning with no codes showing. Thanks