Random Power Loss During Acceleration

[james250]

Need some urgent advice guys, hope someone can help.

I have been experiencing some strange random power loss issues with my 2006 IS250 with 136k miles. The problem is very intermittent that taking it to the dealers doesnt seem like they will be able to replicate the issue.

I've not had any issues with the car until now and owned it from new. When i've been driving for a while and the car warms up, on random occasions the car then becomes hesitant during acceleration. I put my foot down and the car tries to pickup then hesitates and then all of a sudden picks up, by this time i've been overtaken by a micra LOL.

I have been having this issue since last week and eventually the check engine light came on and so i read the code and it read P0127 - Intake Air Temperature Too High. From the research I did, i gathered that the issue was related to the Intake Air Temperature sensor that is incorporated into the MAF sensor, so decided to give that a clean and also cleaned out my throttle body and intake system. Gave the ECU a reset and all was looking fine for a few days until this morning the similar power loss 50minutes into my journey has re-occured. There is no check engine light yet. So, i let the car sit and went for a drive after a while and it was ok again, so it only seems to happen when the car has fully warmed up. And not always, So far from the pattern it does seem like it happens when the car has fully warmed up and i've been driving a little harsh. The days i go easy on the throttle seems the problem doesnt arise.

When i was cleaning the MAF sensor, to be honest the sensor didnt look dirty at all to me but i cleaned it with MAF sensor cleaner anyway. So not sure if it was the MAF sensor causing the issue in the first place.

I did notice my air-filter was very dirty and going to change that out later today, but surely a dirty air filter will not cause these issues when car is warm and throw up error related to Intake Air Temperature?

Would really appreciate some advice and suggestions on this.

Thanks

[Steve]

on the MAF sensor is an ambient air temprature sensor.. this may be gone or needs a clean, but you probably did this when cleaning the MAF anyway

[james250]

on the MAF sensor is an ambient air temprature sensor.. this may be gone or needs a clean, but you probably did this when cleaning the MAF anyway

Yes I cleaned the ambient air temperature sensor thoroughly as per the guide on here. I thought the problem disappeared until today. Now back to square 1 . Also the code P0127 seems to be a Generic Code and not something that is documented in the Lexus DTC document

[Steve]

ok, but it could still be a faulty sensor.

[james250]

ok, but it could still be a faulty sensor.

True, just wondering if i should buy a new or a second-hand one. but having seen the condition of my MAF theres the chance that changing the MAF might end up being a waste of money as it might turn-out to be something else.

[james250]

Could a bad o2 sensor have these kind of effects? Also, i just noticed that the plastic backing of the connector to the MAF is kind of loose. Not the actual connector itself but the plastic cover after the connector. This seems to clip onto the connector itself and seems to easily come off

[james250]

So this morning the problem didnt arise. As the problem seems to be very intermittent, it's very hard to replicate. So i did some data logging via OBD in the beginning of my journey and at the end of my 1hr 15mins journey. On a cold start i got the following readings:

Intake Temperature: 41°F
Intake Ambient Temperature: 34°F

LAMBDA: 1.0 (in the middle between lean and rich - so not rich and not lean - in the green zone)

When i got to my destination, i checked the reading again and the readings were:

Intake Temperature: 105°F
Intake Ambient Temperature: 50°F

Coolant Temperature: 187°F


Would like to see what the reading is when the problem occurs next. So just waiting for this problem to come up again so I can read the data.

Just wondering if anyone knows what would be considered a high Intake Temperature reading?

Also, as my air filter looked a little dirty, decided to replace it.

[james250]

So this morning the symptom came back. But no check engine light yet. It seems that when this problem occurs, when i try to pull off quickly the car seems to not want to go above 2k rpm but then you push it harder then eventually it goes above it and works fine. The problem is very intermittent and occurs occasionally after a while into the journey. But then when the problem occurs, it stays for the rest of the journey until you turn off the car and drive it a little later and it becomes normal after that.

So i checked the sensor readings via the OBD port and they were pretty much the same as when everything was working correctly yesterday. Here is the readings I got:

Intake Temperature: 95°F
Intake Ambient Temperature: 39°F

LAMBDA: 1.0 (In green zone, not lean or rich)

BST/VAC: -10.8psi (The higher the rev, the higher this number goes but in negative)

So based on these readings, it doesnt seem like the MAF sensor is malfanctioning or giving incorrect readings or anything, yet the car still hesitates before it lets me rev above the 2k-rpm. It's a bit like being in snow mode

Any help guys?