Vios---engine RPM erratic when cold start

[Keithchue]

guys,

 

i need advise, for the past 3 days, whenever i cold start my vios, RPM will be erratic. normally, it will rev till approx 1.8k to warm the engine oil and will slowly reduce RPM once it is sufficiently warmed approx 2 mins. now, it is NOT reving when i start it and it will be slowly reving upwards approx 100rpm at a time, and all of sudden shoot to 2k and come down abruptly. meaning to say that the engine is reving it heart out and idling almost at the same time.

any one know what is wrong with it.

 

thanks in advance

[Gondolz06]

u can check wif Hanip Automobiles Pte Ltd at kaki bukit...cheerz....

[Heartbreakid]

The idling valve (or throttle servo) is giving the problem.

[Hungryforcar]

spark plug cable?

[Keithchue]

is it expensive to replace???

[Heartbreakid]

I'm not sure for Toyota, but it shouldn't cost too expensive compared to throttle body, for my case I used to drive Malaysian made car so it is easily below RM100. Let me describe my encounter before you react to the problem.

 

My case was, during good condition when cold start up, rpm would rose to 1.5k rpm. When reached normal operating temperature (between Hot and Cold), rpm drops to around 900rpm. With aircon on, when compressor kicks in, the rpm would jump alittle but maintain at a region of 1000rpm.

 

When this throttle servo gone haywire, during cold start, rpm remains at 1k rpm. When reached normal temperature, rpm rose to 1.5k rpm (Your case sounds similar here). When A/C compressor kicks in, rpm would drop to 1000, when kicks out, rpm would rise to 1500.

 

After the servo replaced, everything back to normal.

[SupperTime]

throttle body idle control valve (below TB) as one member mentioned and a thorough clean of the TB with quality spray should do it. Dont forget to change the gasket.

 

[Keithchue]

this is odd, as i have just did a major servicing including cleaning the TB, if that is the case, i should go back to ask them to clean the idling valve?

[Kb27]

I've cleaned many a idling valve and idling air passage. Usually, they are full of carbon, oily gas and other stuff.

This is make worse by a badly filtering "high performance" air filter.

 

When your throttle plate is closed during idling, the only air passing into the engine is via the idling valve.

 

So when this air passage is blocked or the valve is clogged, then the rpm will go up and down erractically.

Your engine may also stalled sometimes during idling.

[Keithchue]

my mechanic told me that in this case, we need to replace the idling valve, whihc he said would cost about close to 300 including labour...should i go ahead?

[Zuoom]

couple of things to check.

 

MAF sensor - check if in spec. or if too dirty, clean it out.

IACV Idle air control valve is also probably dirty with dirt, oil, gunk, etc.

have it serviced. change all rubber seal, dun use back the old one.