Speed drops to 40 mph

[SaskFJ40]

My wife's LX570 was giving her some problems, she said she would be going along at 110km/h and then it would start slowing down to around 60 and then not go past 4500rpm. Here is what I did and it's been good since (2 weeks). I pulled the plug connected to the accelerator and sprayed it with contact cleaner..... seems to have done the trick, worked for me. We live in an area that gets a lot of snow and I'm thinking maybe some water got in there and started a problem. It wasnt throwing any codes fyi.

Happy trails.

 

[gaijin]

My wife's LX570 was giving her some problems, she said she would be going along at 110km/h and then it would start slowing down to around 60 and then not go past 4500rpm. Here is what I did and it's been good since (2 weeks). I pulled the plug connected to the accelerator and sprayed it with contact cleaner..... seems to have done the trick, worked for me. We live in an area that gets a lot of snow and I'm thinking maybe some water got in there and started a problem. It wasnt throwing any codes fyi.

Happy trails.

4500 RPM @ 60 km/h?

Is that correct?

 

[SaskFJ40]

4500 RPM @ 60 km/h?

Is that correct?

Yes, it would drop with normal rpms but when you feathered the accelerator it would rev up but you wouldnt gain speed, the rpms would climb to 4500 and stop there

 

[DRCocaCola]

How old is it? It sounds like when an old school exhaust is blocked like a disintegrated catalytic converters. A bit of a wild guess but one possibility.

 

[SaskFJ40]

2009. Nah, it seems very..... computery/electronicy in nature, as though there was a limiter or for some reason it triggered the "limp home" mode. Like I said it was happening daily, and since I sprayed the accelerator connection 2 weeks ago it hasnt happened once.

 

[TeCKis300]

Catalytic was my first thought too. There's very few electronic issues with these types of symptoms that won't throw a cell.

The Accelerator Pedal Position Sensor (APPS) and Electronics Throttle Control System intelligent (ETCS-i) are both fail safe systems with redundancy. As they should be because this could be a safety critical type failure.

As said, the accelerator position sensor does have redundant potentiometer/sensors. I believe it has logic that says if one fails, it will limit overall output to something like 25% max, which from your symptoms sounds plausible. It should also throw a CEL.

Could be an internal CEL that doesn't show on the dash, but should show in a code readout. I'd encourage you check it as you really don't want a flaky accelerator component. It could become a safety situation when pulling onto a busy road or merging on the freeway. Failure of both accelerator position sensors means idle output only. I'd replace rather than bandaid fix.

 

[SaskFJ40]

Just a follow up in case people have the same issue. This issue disappeared for 4 years after the initial problem went away. It came back 2 months ago.

Symptom: Intermittently will not accelerate after driving just fine, dropping to 80 kph if driving faster and will rev like it's in neutral but not past 4500rpm. Only happens randomly. No codes. 98% of the time everything is normal.

Possible fix: After a ton of research I suspected the MAF sensor. I have replaced it and so far so good. Will update in the future if this actually was the fix or if problem continues.

 

[KLF]

Sounds like limp mode to me.

Have you checked for any codes stored?

 

[SaskFJ40]

Sounds like limp mode to me.

Have you checked for any codes stored?

Yes that is what I initially thought, I've had limp mode before, this isn't the same as I remember. This also was happening at lower speeds too just less frequently. No codes at all, I even watch the code reader while driving hoping to see some weird readings while it was happening but didn't see anything that looked too abnormal, granted these episodes rarely lasted more than 10 seconds it was hard to tell.

 

[SaskFJ40]

Well I took it to Lexus, they said it's the secondary air injection system, both pumps failed and the control valve is stuck open. They want $5145.00 to fix it...... ya I don't think so. Think I'll do the bypass.

 

[SaskFJ40]

I installed the Hewitt bypass today, I'm used to working on the 40 series so those blind connections at the back of the engine were not fun but alas they ARE possible. Everything went well, now I have an exhaust leak where I installed the block off plate on the drivers side but I'll deal with that tomorrow, other than that things are running great, no limp mode just a new tick I have to sort out but all in all I'm happy to get this taken care of.