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Base idle screw

Tiny
WISH30
  • MEMBER
  • 1999 MERCURY COUGAR
  • 2.0L
  • 4 CYL
  • 2WD
  • MANUAL
  • 300,000 MILES
Does someone know is there any screw for manual base idle adjustment on this type of throttle body? Thanks in advance (988F-FE)
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Saturday, September 18th, 2021 AT 9:01 PM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Hi,

There isn't a base idle adjustment. Idle speed is controlled by the powertrain control module (PCM) via the idle air control valve (IAC).

What is the vehicle doing, idling too high or low? Also, have you tried to service the IAC? Here is a link that shows in general how it's done:

https://www.2carpros.com/articles/idle-air-control-valve-service

Let me know.

Joe

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Saturday, September 18th, 2021 AT 9:36 PM
Tiny
WISH30
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  • 120 POSTS
I have tried to replace IAC valve but with cheap one from Aliexpress. It is the same problem, sometimes stable idle sometimes unstable idle. I suspect maybe it is wiring harness that comes from PCM but it would be too difficult to mount new wires directly from there. Also can I measure somehow the signal stability, I mean if I unplug the valve and put some voltmeter or frequency meter or amperage meter? I tried to unplug the IAC on hot vehicle and it idles perfectly, completely perfectly. I decided to drive without IAC, but when started on cold vehicle, it immediately turns off if the gas pedal is not pressed because IAC is closed by default.
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Saturday, September 18th, 2021 AT 9:45 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Hi,

If you are checking the wiring, the easiest thing to do is move the wires around to see if the voltage jumps around.

Are you sure the IAC you got is good? I have seen so many faulty, inexpensive parts lately. The idea that it ran well when it was warmed up leads me to believe it's the sensor. Also, did you notice if there was any carbon or dirt where the IAC mounts?

Let me know.

Joe
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Sunday, September 19th, 2021 AT 5:55 PM
Tiny
WISH30
  • MEMBER
  • 120 POSTS
It runs okay when warmed up (but IAC unplugged from harness). What sensor do you mean? There was not any dirt everything was clear.
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Tuesday, September 21st, 2021 AT 3:53 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Hi,

I was referring to the IAC sensor/motor.

If you look at the attachments below, they are three different sets of diagnostics specific to the IAC. Each one is based on different possible issues.

Take a look through this and let me know if anything helps.

Also, if you have a scan tool that can provide live data information, let me know what the coolant temp sensor is signaling and what the short term fuel trims are.

Let me know.

Joe

See pics below.
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Tuesday, September 21st, 2021 AT 4:16 PM
Tiny
WISH30
  • MEMBER
  • 120 POSTS
Just one more question please, because purge valve is a new thing for me, where is it located? Thanks in advance.
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Wednesday, September 22nd, 2021 AT 3:41 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Hi,

No problem. It's under the hood below the air box. I attached the directions for removal and replacement.

Let me know if this helps or if you have other questions.

Take care,

Joe
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Wednesday, September 22nd, 2021 AT 3:14 PM
Tiny
WISH30
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So, as I can understand from drawings, it is near to the EGR controlling solenoid valve.
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Wednesday, September 22nd, 2021 AT 8:26 PM
Tiny
MASTER ASE TECH
  • MEMBER
  • 82 POSTS
The purge valve itself is near that, it has 2 vacuum lines going to it that are about the width of a pinky finger. Also most cars have a plastic line that will have a green cap on it for the purge line. Follow this line to the purge valve.
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Thursday, September 23rd, 2021 AT 11:41 AM
Tiny
WISH30
  • MEMBER
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And what about the canister location, is it somewhere near the fuel tank or somewhere in the front? (Sorry for asking too many questions, but I must be theoretically prepared first because these 3-4 days I am not able to look directly on the car - it is on service as usual :) this time for AC leaking, this is fifth time for the same problem because here in Macedonia mechanics are so good.
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Thursday, September 23rd, 2021 AT 4:13 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

The evap canister is near the fuel tank. See pic 1 below. There is a canister carrier that holds it on the vehicle that will need to be removed to access the canister. See pic 2

Once the carrier is removed, you will see two vapor tubes (pic 3) and the canister vent solenoid.

Let me know if this helps or if you have other questions.

Take care,

Joe

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Thursday, September 23rd, 2021 AT 5:11 PM

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