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High idle RPM just after throttle body cleaning

Tiny
NFORNAUMAN
  • MEMBER
  • 2014 HONDA FIT
  • 1.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 30,000 MILES
My Hybrid had about 28 km/liter mileage. But then my mechanic cleaned the throttle body as a routine checkup. Just after that, the mileage dropped to 15 km/liter. I have it scanned and it has 1,200 idle rpm. But the mechanic is unable to understand the reason of sudden poor mileage and high idle rpm. Can someone suggest what might have happened?
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Friday, May 11th, 2018 AT 10:09 AM

11 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
I am wondering if he cleaned it on the car which is a no no because the chemical cleaner can effect the A/F sensor and the oxygen sensors. It could go back to normal after a few miles of driving. Do you have check engine light on? If so lets get he codes to see what happened.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Here is the A/F sensor location and a guide to show you what you are in for when changing the sensor:

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Please run down these guides and diagrams and report back.

Cheers, Ken
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Sunday, May 13th, 2018 AT 2:10 PM
Tiny
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The high idle (1,200 rpm's) and poor mileage issue is still there, even after 2,000 km driving after the throttle body cleaning. There is no check light. The mechanic opened the throttle body and cleaned it away from the car.
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Sunday, June 3rd, 2018 AT 1:45 AM
Tiny
KEN L
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Even though there is no check engine light there still can be codes. Lets run them to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.

Cheers, Ken
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Sunday, June 3rd, 2018 AT 11:36 AM
Tiny
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I did as per your instructions. There are no fault codes.
Mileage is still very poor within city traffic. It is better on highways (although not like before).
Some adjustments has been disturbed, which mechanic is not able to understand. He says that car is not accepting idle learn procedure.
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Monday, June 18th, 2018 AT 9:05 AM
Tiny
KEN L
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It sounds like the air fuel sensor is not working right I would replace it and see what happens. Here is a guide and diagrams to help you:

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

Check out the diagrams (below). Please let us know what you find.

Cheers, Ken
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Monday, June 18th, 2018 AT 10:43 AM
Tiny
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I am trying to do it myself and thus greatly appreciate your help.
You talk of A/F sensor, but the given link is about oxygen sensor. Are both same? As I initially thought that A/F sensor is MAF sensor.
Do you suspect that A/F, or oxygen sensor may have been disturbed by the mechanic during throttle body removal/installation?
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Monday, June 18th, 2018 AT 8:18 PM
Tiny
KEN L
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Yes I do, I have seen the problem before. The AF sensor does the same job as the oxygen sensor.
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Tuesday, June 19th, 2018 AT 10:59 AM
Tiny
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1. There was no effect on replacing air fuel sensor.
2. I removed throttle body. The butterfly was observed to be slightly open. Mechanic says that when throttle body was initially cleaned and later fixed without doing calibration; it has adjusted itself in slightly-open position. Now computer thinks that accelerator pedal is pressed (as butterfly is slightly open), and it thus causes high rpm than usual. This causes more effect at low speeds and thus poor mileage.
3. Have you seen this kind of problem? What is the remedy?
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Thursday, July 12th, 2018 AT 9:43 AM
Tiny
KEN L
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If he removed the throttle body with the key on of the battery still connected the throttle actuator with need to be reinitialized. Are there any codes? Lets run then to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.

Cheers, Ken
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Friday, July 13th, 2018 AT 6:09 PM
Tiny
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There are no codes. There is no check light either. That is one reason mechanics are not able to understand the problem.
Mileage is now less than half of what it was before throttle body cleaning.
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Friday, July 13th, 2018 AT 9:37 PM
Tiny
KEN L
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It sound like the actuator will need to be re-initialized. It will cost about $130.00 at the shop.
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Saturday, July 14th, 2018 AT 2:54 PM

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