Car idling high

H

HavocXphere

Honorary Master
Joined
Oct 19, 2007
Messages
33,153
Reaction score
1,297
Location
Europe
I've got an old polo that idles just fine, but for the first ~3 mins after starting it idles at 1.6k rather 1.1k that seems to be "normal".

Doesn't seem to cause a direct problem, but I'd still like to know whats causing this because I vaguely recall that it hasn't always done this.

Thoughts?
 
Most cars have an automatic choke that increases the fuel flow (read: revs) when the engine is cold. This reverts to normal after two or three minutes.

NB: The definition of a "cold" engine will vary between manufacturers :)

Given that we are in the middle of winter I would expect the automatic choke to be invoked when you start the car first thing in the morning. OTOH it shouldn't be used if you start the car around lunch-time unless it is a particularly cold day.

If your car now always starts with higher revs you have a problem.
 
Last edited:
My car is also idling 1500rpm at cold startup. Drops to 1000rpm when water temp gets to normal.

Summer startup is approx 1250rpm
 
Rickster said:
Above 1000 is still high when warm, it should be 850-900.
Click to expand...
Pretty sure that on my car 1.1k is the "normal" idle....below 1k the car feels like its near stalling.

Seriously said:
Not if it changed from the norm. Best to call a service mechanic just to confirm and check duration of said action.
Click to expand...
Will def highlight it on the next service...the behaviour seems to be somewhat in line with what you & others described though so I think I can safely let it be till the next service (plus 1.6k isn't going to cause damage).

Anyway...thanks all - got the answer I wanted.
 
1.1 is too high. Normal idle should be in the 800s. You may have a vacuum leak.
 
Well its made it through a couple years of official VW services with the 1.1k idle but I'll ask next time.
 
Do you park outside or in a garage?

Pretty normal for cars to idle high when they are cold, especially fuel injected ones.

But like Sinbad says your default idle seems way too high, which might mean the automatic choke option just makes it go extra high.
 
Inside...though kinda drafty garage so temp approximates outside minus the hectic frost etc
 
Sinbad said:
1.1 is too high. Normal idle should be in the 800s. You may have a vacuum leak.
Click to expand...

What is the cause when my Mazda sting is idling below 600 since it seems to happen every 8000 km and it stalls if I don't rev the car or put it in neutral at the robots or on inclines.

If I put the aircon on it chokes out and stalls straight away if stopped or going to stop at a robot or slowing down for speed humps.

It usually is above 800 in working condition after a service and I think it is fuel injected if I remember right.
 
Last edited:
grantza said:
does this happen on every start-up (even when already warm) , or just when the car is cold ?
Click to expand...
Just when cold I guess...cold being hasn't run in the last 60 mins rather than weather cold. Don't recall whether it did this during warm weather.
 
HavocXphere said:
Just when cold I guess...cold being hasn't run in the last 60 mins rather than weather cold. Don't recall whether it did this during warm weather.
Click to expand...

As you know, I am no grease monkey, I'm better suited to a soufflé dish than a spanner - but here goes . . .


Two things have been mentioned.
1) thermostat
2) automatic choke

Thermostat:
On a cold start, the thermostat is only partially open, restricting the full flow of coolant to allow the car to warm up correctly.
When the car is warm, the thermostat is fully open, full flow of coolant passes through the cooling system.
Often when cars overheat, the thermostat may be stuck in the closed position, thus restricting the flow of coolant through the system.
The thermostat will not usually cause the change in idle speed you are experiencing.

Choke:
With the automatic choke, in cold weather, the choke opens, it's similar to applying slight pressure to the accelerator while the car is idling.
This allows the car to war up a little quicker.
So in the morning when the car is cold, the choke will open, your idle speed will increase a little.
After a few minutes of driving, the car would have warmed up. If you then put the car in neutral, you should notice your idle speed is normal (as you were accustomed).
So lets say you start the car in the morning (cold) the automatic choke will open, idle speed will increase slightly, you drive to the shop 5 minutes away. You come back to the car (it is still warm) start up, you should notice the idle speed is normal, not as high as it was when you first started.

So I am guessing you are noticing the automatic choke operating how it should on cold starts in crappy weather.

It does seem the idle speed is a little higher than it should be though. Normally would be around 700-800rpm.(manual cars)
The automatic choke, when on, will push the idle speed up a little 900-1000rpm.
You may find the car is using a little more fuel than usual
 
Newer cars stock idle is 750-900rpm

Older cars 1000rpm to - , even higher, if you have carbs.

Modded car, it could be anything, as set by tuner.

PS check your ICV. apparently they gum up on the older polos, a few squirts of carbie cleaner and you should be good to go.
 
Last edited:
Sinbad said:
1.1 is too high. Normal idle should be in the 800s. You may have a vacuum leak.
Click to expand...

Newer cars adjust their idling depending on their conditions. On cold start-ups it's not abnormal for a vehicle to idle above 1000rpm until it reaches temperature.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X