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Motor Bogs Down With Hot Air Intake Temps

5671 Views 14 Replies 12 Participants Last post by  davect01
If it's hot outside (90F+) and you're sitting at the light so the air under the hood gets hot then try to accelerate, the engine bogs down and you go nowhere crawling forward very very slowly. Other cars aren't remotely this bad with hot temps. What's going on?
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Also I've noticed the cooling fan never ever turns on. Only exception is when the AC is running. Was the ECU programmed to keep the engine running super cool and super low power and when temps go up it cranks down the power even further to almost nothing?
I wonder if a vented hood would help with this.
What transmission do you have? I have not experienced this on mine.

As for the ECU programming the world will never know Toyota ECUs are uncrackable.
What transmission do you have? I have not experienced this on mine.

As for the ECU programming the world will never know Toyota ECUs are uncrackable.
I have the CVT. It's super, super slow. Once the car gets going it's ok or if I'm only stopped briefly and the ambient air hasn't had time to heat soak yet.
Isn't the air is drawn from the wheel well?
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Have the CVT as well, I can say as well if it's 90F+ it's bad, at a stop then drive the car accelerates really slow. Sports mode ( though I don't see why I have to press it) kinda kicks it but the acceleration isn't there unlike with night time, it's like peppy. Literally night and day, literally ...
I find CVT very slow to accelerate in Eco mode even in a lot colder temps. It's slow to the point that most days in city traffic I use sport mode all the time.
My experience with the iM (Cvt as well) it has bogged a lil when at a stop or yielding into traffic.. I once yielded into a lane at a stop semi-mashing the petal the motor felt as if it had turbo lag before even moving (although there is no turbo..)
The standard transmission does not have this problem really
Maybe wire a secondary switch to the fan to see if it helps ?
For the past week or two, it has been 90+ degrees here in Murrieta CA. I know many of you will disagree but I filled up the iM (6spd man)with 89 octane gas from chevron (currently on 3rd tank). It helped get rid off the bog down. Also, dramatically reduced engine noise and vibration. Rev hanging is gone (shifting is right on on every gears with no clutch adjustment).

Power change is hardly noticeable but my mpg is surprisingly increased to 38-39 mpg (city driving with 3500 rpm average shifting and 70-75 mph freeway).

The intake and exhaust sound is much deeper on 87 than 89.

I will be filling up and going back with 87 octane this weekend for further evaluation.

This is just my experiment. My Tiburon and MK3 supra runs better and cleaner on 87 octane (never failed smog). I just tried the 89 on the iM since I have never tried it since I owned the car.
For the past week or two, it has been 90+ degrees here in Murrieta CA. I know many of you will disagree but I filled up the iM (6spd man)with 89 octane gas from chevron (currently on 3rd tank). It helped get rid off the bog down. Also, dramatically reduced engine noise and vibration. Rev hanging is gone (shifting is right on on every gears with no clutch adjustment).

Power change is hardly noticeable but my mpg is surprisingly increased to 38-39 mpg (city driving with 3500 rpm average shifting and 70-75 mph freeway).

The intake and exhaust sound is much deeper on 87 than 89.

I will be filling up and going back with 87 octane this weekend for further evaluation.

This is just my experiment. My Tiburon and MK3 supra runs better and cleaner on 87 octane (never failed smog). I just tried the 89 on the iM since I have never tried it since I owned the car.
B91SUPRA I look forward to your next post on this! ?
Thanks for the post. I will also try to experiment with my car in the heat as I also have the CVT. I haven't really noticed anything yet of bogging down but yes you could always wire it so that the fan stays on all the time or have an auxiliary switch like MiScion said . I've done that on my old 300zx twin turbo and it made a world of difference. The only problem with that is if you lived in a place where it snowed and need the motor to warm up.
Someone posted about sport mode and honestly that's all I drive in if I'm using the automatic. Sport mode kicks butt comparative economy mode. My 2012 Mercedes C250 (turbocharged) was the same way, had to drive it in sport mode all the time to get any decent power (of course not as good gas mileage).
Otherwise, if I want to have better control of my power I go over to manual shifting and drive around town revving it up between 3000 and 6000 to get better power. I'm also more likely to use manual shifting when I'm in traffic that way I can downshift and use less brake. I feel more in control that way. I was just thinking that some of you guys that own automatics might not even know how to drive manuals and are aware of how to shift. I think you'd be missing out on that part of the experience of this car.
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weighing in

Thanks for the post. I will also try to experiment with my car in the heat as I also have the CVT. I haven't really noticed anything yet of bogging down but yes you could always wire it so that the fan stays on all the time or have an auxiliary switch like MiScion said . I've done that on my old 300zx twin turbo and it made a world of difference. The only problem with that is if you lived in a place where it snowed and need the motor to warm up.
Someone posted about sport mode and honestly that's all I drive in if I'm using the automatic. Sport mode kicks butt comparative economy mode. My 2012 Mercedes C250 (turbocharged) was the same way, had to drive it in sport mode all the time to get any decent power (of course not as good gas mileage).
Otherwise, if I want to have better control of my power I go over to manual shifting and drive around town revving it up between 3000 and 6000 to get better power. I'm also more likely to use manual shifting when I'm in traffic that way I can downshift and use less brake. I feel more in control that way. I was just thinking that some of you guys that own automatics might not even know how to drive manuals and are aware of how to shift. I think you'd be missing out on that part of the experience of this car.
O.K. I'll weigh in.

I have hardly noticed a power difference with the A/C on, (A must when it is 110 F). I have noticed a slight drop in MPG, down from 33 to 31.

And yes, anytime I have to accelerate, (like going onto an onramp), I pop over into sport mode.
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