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Idle speed

Tiny
ZEMORZEMOR
  • MEMBER
  • 2000 MAZDA PROTEGE
  • 1.6L
  • 4 CYL
  • 2WD
  • MANUAL
  • 180,000 MILES
The idle speed is at 850 with all accessories off. In the sticker underneath the hood it says it should be 700. What are the causes? I checked for vacuum leak, none. Do I need to adjust minimum idle by adjusting air idle screw? If yes what are the steps?

Thank you
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Friday, April 27th, 2018 AT 5:24 PM

10 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,291 POSTS
At that many miles, I cannot say that I would mess with it. If it runs decent, just keep it going. Could just be an inaccurate reading on your tachometer. If you really want to check into it, use a scanner with live data mode to see what idle speed it shows.
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Friday, April 27th, 2018 AT 7:04 PM
Tiny
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Yes, I checked it with live data.
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Friday, April 27th, 2018 AT 7:07 PM
Tiny
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TPS percent 0 percent, engine speed 850.
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Friday, April 27th, 2018 AT 7:08 PM
Tiny
HARRY P
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Vacuum leak (which you already ruled out), intake manifold gasket leak, fuel pressure regulator, and IAC valve and bore need cleaning or the valve needs replacing. Those are the things that come to mind for me.
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Friday, April 27th, 2018 AT 7:20 PM
Tiny
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The idle rpm went up after cleaning the throttle body, after that decided to clean the IAC valve. I checked for vacuum leak on all the engine even on the oil dip stick. At idle LTFT is 3%
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Saturday, April 28th, 2018 AT 4:35 AM
Tiny
HARRY P
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Did you take the throttle body off when you cleaned it? If so I would suspect a leaking throttle body base gasket.
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Saturday, April 28th, 2018 AT 7:39 PM
Tiny
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Yes I did took it off and I replaced the gasket. I checked for vacuum leak by spraying carburetor clean and watching short term fuel trim if they go negative which it did not. I did same think for all the vacuum hoses and air intake even oil dip stick. What I saw when cleaning the throttle body it was chunk of black whatever in the idle air hole when I sprayed carburetor clean. Other thing I noticed is the inside where the throttle plate rides there are scratches and black marks from I guess opening and closing the throttle plate. Also, I took of the IAC valve and cleaned it and replaced the gasket no vacuum leak.
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Saturday, April 28th, 2018 AT 8:50 PM
Tiny
HARRY P
  • MECHANIC
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Well then the only thing left to do, as far as I can tell, is to turn the air adjusting screw on the throttle body. Prodemand does not tell exactly it is, or which way to turn it. So you will have to do some trial and error. Do that and let us know how it goes for you.
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Sunday, April 29th, 2018 AT 3:42 AM
Tiny
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Can a leaky oil pan gasket makes vacuum leak?
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Sunday, April 29th, 2018 AT 8:58 AM
Tiny
HARRY P
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No, it is not under any vacuum pressure.
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Sunday, April 29th, 2018 AT 6:22 PM

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