Idling Problem

Tiny
C4PRLM4ST3R
  • MEMBER
  • 2006 PROTON
  • 4 CYL
  • 2WD
  • MANUAL
  • 180,000 MILES
Hi guys.I am driving local made car by PROTON. One of Malaysian national car maker. How ever the engine using 4G18 engine by Mitsubishi. Recently water goes inside my engine bay. I already done engine overhauling inclusive replacing one of the piston liner. The machine shop who done the job have checked everything and confirmed that my engine block and head in good condition. After fix everything working fine except my idling going crazy. So I went to scan my ECU to make sure it is ok. The mechabic say my ECU fine but the throttle body fault already. My idling jumping from 500 to 1000rpm and it sound like boiling water. So I tried seek for 2nd opinion, but they keep saying the say same thing. Throttel body!So I go for changing it to new one. Now the idling stable but I cannot get it below 1000rpm. It stay about 1500rpm and lower down to 900+ when I turn on AC. Can ECU cause the problem?Does the ECU control the amount of fuel injected?Thanks.
Thursday, June 2nd, 2011 AT 1:41 PM

9 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Have you tried adjusting the idling speed?

Did you check for vacuum leakages?

The ECU controls almost everything connected to engine operations and performance but it acts according to signals from the various sensors.
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Thursday, June 2nd, 2011 AT 3:50 PM
Tiny
C4PRLM4ST3R
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Yap. But the idling still like that.I have check every hose. Just shut one end and blow the hose. Can manifold lead cause it?Can I apply gasket glue to the manifold?
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Thursday, June 2nd, 2011 AT 4:13 PM
Tiny
KHLOW2008
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If the manifold is leaking, the idling speed would definitely increase. So wou clogged coolant hoses to the IAC (throttle body)

Use carb spray to detect leaks with engine running.

Sealant is not recommended but ou can use it if you think it is going to work.
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Thursday, June 2nd, 2011 AT 4:29 PM
Tiny
C4PRLM4ST3R
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Thanks bro

i will tried to do it and get back to you if any change.
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Thursday, June 2nd, 2011 AT 4:49 PM
Tiny
KHLOW2008
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If the replacement throttle body is a used unit, I would not discount the possibility of it being faulty. Used units tends to get stuck when they are kept for prolonged periods.
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+1
Thursday, June 2nd, 2011 AT 6:33 PM
Tiny
C4PRLM4ST3R
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It is a new unit. My mechanic try to swap it to verify the problem. After that we noticed that idling stable but at 1500rpm. It is ok if I just blown out the hose and close one end to check for leakage?Any other way?
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Friday, June 3rd, 2011 AT 9:29 AM
Tiny
KHLOW2008
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Yes, you can do that but not too high pressure.

Does unplugging the IAC wire connector results in any changes in the idkling rpm?
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Friday, June 3rd, 2011 AT 1:02 PM
Tiny
C4PRLM4ST3R
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Just went to c other mechanic today. He tried to take out TB solenoid connecto (it is this is IAC?) But nothing happen. So he ask me went to Proton SC to reset back all setting. He claim every time change the solenoid must retune setting. So I can just went to SC on monday and see how the result.
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Saturday, June 4th, 2011 AT 8:59 AM
Tiny
KHLOW2008
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It is not necessary to reset the IAC. Disconnect the battery and wait 10 seconds or more before reconnecting.

Start engine with all accessories turned off and allow to run until the radiator fan comes. Turn on A/C and run for another five minutes and retest.

The PCM will self relearn.
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Saturday, June 4th, 2011 AT 10:45 AM

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