Power loss ocassionally

Tiny
ICERUS
  • MEMBER
  • 2003 LEXUS RX 300
  • 3.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
Hello, I own the vehicle listed above (gen.2 since 2003-2009). I don't know is it linked problem, but sometimes car can't start up from first time and other days starts normally. Alternator charging is 13.4V on idle, but it keeps draining battery to 40%. But the real problem is that car with 150kW sometimes act like it has only 50kW. One day it drives like crazy and the other it lacks of power. Sometimes even in the same trip it lose power and gain it again during ride. No dashboard warning lights or codes. I changed spark plugs, vacuum pipes, clean throttle body and MAF sensor. Charge battery to 100%. Engine, transmission, differential oil and filters changed. When it has no power, I noticed louder sound like engine struggles, lower fuel economy, harder or unable to reach 180kmh and next day it just works fine. Lot quieter, faster, better fuel economy, easily reaching 180kmh and great throttle response. What should I replace or fix to enjoy ride again?
Sunday, June 7th, 2020 AT 9:11 AM

13 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Does the transmission shift properly?

https://www.2carpros.com/articles/automatic-transmission-problems

This sounds like the transmission is either not up-shifting correctly or is sticking in one gear that is making it have lower power.

https://www.2carpros.com/articles/engine-has-low-power-output

https://www.2carpros.com/articles/symptoms-of-low-engine-power

Roy
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+1
Sunday, June 7th, 2020 AT 2:26 PM
Tiny
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Thanks for quick reply. Transmission shifts pretty fine and goes into every gear nicely. Few months ago there was a problem with one vacuum hose. It keeps falling of connector and when I put it back it restores power. But now I tighten it harder so it doesn't fall off. But still there is power loss problem and I can't see any vacuum lines fell off. Any other suggestions?
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Monday, June 8th, 2020 AT 1:24 PM
Tiny
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Are there any codes set in the system?

Do you have a scan tool that can read live engine data?

Roy
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Monday, June 8th, 2020 AT 1:42 PM
Tiny
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Thanks Roy. No there is no codes in the system. I have scan tool and Techstream to read live engine data. What should I look for?
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Tuesday, June 9th, 2020 AT 7:04 AM
Tiny
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You had mentioned about vacuum lines. Can you give me the long term trim readings in percentage for bank 1 and bank 2?

Roy
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Tuesday, June 9th, 2020 AT 7:18 AM
Tiny
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Here are screenshots from Techstream with long term readings and all other data. I hope you will find some clue about power loss based on this. Forwardly grateful.
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Tuesday, June 9th, 2020 AT 11:29 AM
Tiny
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Too small to see. Can you just tell me the long term trim percentage?

Roy
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Tuesday, June 9th, 2020 AT 12:22 PM
Tiny
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Sorry for bad pics. Here is data you need:
Long FT#1 -1.60%
Long FT#2 -0.82%
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Tuesday, June 9th, 2020 AT 12:34 PM
Tiny
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No worries.

The trims are good.

I still think the issue is involving the transmission.

Roy
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Tuesday, June 9th, 2020 AT 12:40 PM
Tiny
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If I use manual shifting (S mode) and use second gear with speed of 70 kmh and press full throttle there is no gear shifts because it has already selected optimal gear for that speed so it should pull right away but sometimes it is sluggish and sometimes it is like rocket. That is what confuses me. Is there anything I can do to test transmission?
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Tuesday, June 9th, 2020 AT 12:51 PM
Tiny
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No, not you. That would need to be done by someone with a scan tool to monitor the live data from the transmission.

I would let a transmission shop drive the car and give you there opinion.

Roy
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Tuesday, June 9th, 2020 AT 1:07 PM
Tiny
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Thanks Roy, I will try that. Best regards.
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Tuesday, June 9th, 2020 AT 1:10 PM
Tiny
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You are welcome.

Always glad to help.

Roy
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Tuesday, June 9th, 2020 AT 1:22 PM

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