NJ 3.0 high idle when cold

[macpajero]

Have an issue and wondering any ideas from the community.
NJ 95 3.0 285,000K
2 months approx.When cold engine idle at 2000 rpm, thermo fan operates.
About 30-45 secs later, thermo fan shuts down and as it slowly warms, idle starts to come down to eventually, normal idle rpm.
This process to normal idle is, 1-1.5min approx.
Appreciate any ideas or the cause!
Cheers

[Pauly Faulkner]

A throttle body clean is a good start as it's most likely a stuck/dirty fast idle valve and iac valve. Check the fast idle valve coolant passage isn't blocked as well (bottom of throttle body).

Common to see up around 1800-2000rpm on cold start breifly then back to around 1300-1500rpm if you don't touch accelerator, if you touch accelerator it can jump back up again breifly then settle back again and keep doing this until fast idle air valve shuts as the throttle body warms up.

[my.paj]

The fan you are talking about is the one for the air cond in front of the radiator ?
If so something is telling it to turn on but if the car is cold it should not be running, thats my limit.
Rick

[dolphin]

buy some Throttle body cleaner and some Air Intake Foaming clean. these will both clean the throttle body and the phenlin chamber . also remove and spray clean [ with throttle body cleaner ] the Idle Speed Control unit which is mounted on the side of throttle body.

[macpajero]

Yes, it is the one in front of radiator.
Will have to dig deeper to see why it is operating when cold.
Cheers

[macpajero]

Ok thanks for the info and advice.
Will get to work and use the suggestions put forward.

Let you know the outcome.
Cheers

[macpajero]

Looks like the cleaning the throttle body is the first area that requires attention.
Then progress if that fails.
I'll find it!!

Thanks

[Bogger]

I think Mypaj is on the right track .......... I'd check air con switch for fault as given the cold weather in Vic it wouldn't take long for the air con to cycle off cutting out air con as it reaches temp (air con cold cut off temp not engine) and hence dropping idle speed. Let idle for quite awhile and see if air con cycles in and out ? It sounds like your air con is permanently on which is upping the idle speed as it's designed to do.
Pull air con fuse and see if it fixes idle issue would be a good way to isolate the fault.

[P-E-T-E-]

Ok two questions

1: When you say "thermo fan in front of the radiator" i assume your not talking about the radiator clutch fan that is attached to the motor

2: when the engine is warm does it idle between 800-900RPM?

[AndyNH91]

The two coolant hoses that go to your throttle body go into the Fast Idle Air Valve (FIAV). Works much like your thermostat except it is designed to close as the coolant temperature increases. The valve that it closes off is an air bypass to your throttle body i.e. lets more air in to the engine while the coolant is cold, hence the faster RPM. You can read about its operation in the factory service manual or the Gregory's / Haynes if you are keen.

It is adjustable, but it's a bit of a pig to get to the adjustment. You need to pry the disc out of the end of it, then unwind the collar with a set of needle nose pliers and then screw the plunger head out so that it closes the valve at a lower temperature.

No harm in the behaviour of the engine as you describe it though.

[AndyNH91]

I guess the other way to look at it is... faster revs when the engine is cold, means it burns a bit more fuel, hence more heat and thus gets up to operating temperature faster. This is a good thing, and is a commonly misunderstood design goal of the cooling system i.e don't let the engine overheat, but at the same time allow the engine to reach operating temperature of say 80-90degC as quick as possible. This is also why you have a thermostat, so the radiator can be isolated when the car is below operating temperature. Too cold an engine is a problem as well as too hot an engine. Make sense?

[P-E-T-E-]

if the electric fan is on in the front of the car then i would say your A/C system might be playing up.

[AndyNH91]

if the electric fan is on in the front of the car then i would say your A/C system might be playing up.

If you wanted to fix something, I think Pete is on the right track. Pretty sure the condenser fan shouldn't be on if your A/C is switched off at the dash.

[ohnyou]

Hi
Just a question, can i close that hole in the middle completly so the car is idleling when cold with the normal revs?

[P-E-T-E-]

when the air con is activated the A/C system will automatically increase engine RPM to help the pump operate more efficiently