[Mk2] [NA] Rough idle when warm (help to check idle control parts)

[Peterwolf]

I got a MK2 NA Rev2 and since I got them I notice a problem with idling.

When the engine is cold the idle is set to higher RPM and once it's warm it drops to 850RPM+-, the normal procedure.

But when the engine is warm sometimes I notice the rough idle between 750/950RPM+-. Is not always, it can idle perfectly or sometimes have rough idle.

I think that's some problem with the Idle Control Valve or something related.

The mechanical part of the ICV at the throttle body has been checked and cleaned but the problem continues.

http://www.toyodiy.com/parts/p_E_1992_T ... l?hl=22270

http://www.toyodiy.com/parts/p_E_1992_T ... ?hl=25740S

Between the two links, what part can cause this problem?

Thanks!

[JeffD]

You could always try cleaning it - have a looky here

http://www.imoc.co.uk/forums/viewtopic. ... light=iscv

[Peterwolf]

The mechanical part of the ICV has been cleaned, and looks like is ok. Can it be a problem in the electrical part of te ICV (where the connector is plugged)?

Also, justo to help diagnose, the coolant system was been entirely rebuilt, the ignition parts (rotor, dizzy cap, leads and plugs) are new, and the engine has 3 more ground points than standard.

The previous owner told me that the car need a new ICV valve, but thats the ICV that are in the throttle body, or the other part that is under the intake manifold?

[JeffD]

Ive not had problems myself but IIRC some people have experienced problems you describe if the cooling system was not bled properly - coolant actually runs through bottom of throttle body

[Peterwolf]

Bridged the E1-TE1 terminals and the engine lights blinks continuously. So, no problem with error code.

I doubt that's a problem with the cooling systems, because the rough idle problem happened before and after I renew the entire cooling system.

Thanks for the tips, I will keep searching for what can cause the problem.

[Driftlimits Performance]

Will be Iscv and tps calibration I reckon.

[stevenb]

Will be Iscv and tps calibration I reckon.

Hi Luke,
Do you mean the timing needs adjustment?
ISCV = what does that stand for?

Cheers

Steve (Dunstable)

[JeffD]

ISCV = Idle Speed Control Valve

There's a pic on the thread I've linked to

[stevenb]

Cheers Jeff.

So in a nutshell. Leave the sensors attached (unless they are damaged like yours was) and remove the unit instead for a good clean up.

[JeffD]

thats what Id do as the first step :-)

plus also check for damage to the throttle body gasket - mine a split in

[stevenb]

I bought my car off a lady who'd owned it since '99 and she never lifted the engine bay lid so I'm guessing mine is just dirty.
Car certainly hasn't been abused.

[Peterwolf]

Just to update the situation.

I replaced the ISCV - the electrical part only ( http://www.imoc.co.uk/forums/viewtopic.php?t=153753 ) and the rough idle disapeared.
But with that I got a new symptom...
Now at cold it idles at 2000RPM (normal behavior), then drops and keeps stable at 1000RPM when warm, and not the standard 850RPM.

What can it be? Is any way to tune the idle?

[JeffD]

Did you clean all the throttle body up too?

Also, did you adjust the throttle in any way while it had the original fault?

[Peterwolf]

Yes, the TB and ISCV were cleaned.

In my hands the car didn't had any adjustment in the throttle, related to this just the cleaning of the TB/ISCV and the ISCV electrical part replacement.

But I don't know if the previous owner did any adjustment.

But the car feels ok pulling at full throttle, and cruising normally. The only problem is related to the idling.

[stevenb]

If the car is running and idling smoothly and accelerates ok then it maybe the tacho might be mis-reading.
Are these electric tacho's or gearbox driven on the rev 2?

[Peterwolf]

I think that Rev2 are equal to Rev3 and so on.

Before I change the ISCV the idle are at 850RPM+- but with rough idle, up and down... Now with the ISCV replaced the idle is stable, but at 1000RPM.

[stevenb]

When did you last get the ignition timing checked?
Might be worth checking that too.

[Peterwolf]

A month or two ago, when I replaced the the ignition parts (rotor, dizzy cap, leads and plugs).

Is possible to tune the idle in Rev2 MK2 NA?

[stevenb]

Not sure.
Does the inlet manifold have butterfly valves?
If so, you might have a sticking valve and it might just need de-coking/cleaning...

[JeffD]

Did you deffo make sure this was clean?