What do idle speeds have to do with passing a smog check? My repair place said it wouldn't pass unless the idle speed was lowered.


Asked by Feb 16, 2015 at 11:18 PM about the 1992 Toyota Hilux

Question type: Maintenance & Repair

Need help ASAP

10 Answers


Sheesh, how many years do you have to pass smog in your state? Only a small part of my state even requires smog testing and it only applies for 10 model years then they go exempt. But to answer your question, idle speed will cause you to fail the test, it is and indication that something is not set properly or there is a mal - function in the engine control systems. Did they do a computer test?


Shouldn't the tech be able to set the idle at a lower speed to do a smog test?


Only if nothing else is wrong.


My car hasn't failed a smog since I bought it 24 years ago. Have the requirements for idle speeds changed? And it passed somewhere else, no repairs were recommended.


So exactly what is the idle speed?


It was 1500 and I had it lowered to 1000.


Base idle is 850 +or- 50. I would have the ECM checked for codes, you may have a sensor out of specs causing the idle to creep up.


EMC? What is that? Two mechanics said the emission control devices were working okay.


ECM Is the computer, but you say it has already been checked. Did anyone find out why the idle speed was high? Stuck decel valve or a cracked vacuum line.


No one found any cracked vacuum hose. The decel valve might have been corrected to lower the idle speed.

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