Help Erratic Idle

[nrvmotorsport]

Hey everyone, right i've had this problem for about a year now. All started when the wading inside my old backbox fell apart and blocked the exhaust causing it the gases to come back into the cat and engine. During the time of limping home, gettin overtaken on hills by lorries, the idle once engine is warm goes from 800rpm to 1500rpm constantly.

I have done the obvious and got another icv and still had the same problem. I have changed the throttle body with no effect also.

We discovered the icv was having problems knowing whether to be open or closed. Hence this jumping revs.

Does anyone know of any sensors on a Honda Civic that may cause this. I am gonna get a new Intake Air Temp Sensor to try and maybe a coolant temp sensor.

It only does this once the engine has warmed up telling me it isn't the icv but something that talks to the icv. Something that may have got damaged by the exhaust gases, lambda sensor and cat reads fine as passed mot.

Oh yeah other thing is, I had the icv blanked where the air and water runs through and it didn't idle at all which is what was expected so again i dont think its the icv.

Other things done -
Changed the whole head and relevant gaskets. Still on now.
Changed intake manifold and throttle body. Still on now.
Resistances have been checked on sensors.
Dizzy n rotor arm have been replaced.
HT Leads have been replaced.
Spark plugs have been replaced.
ICV has been replaced.

All ideas will be appreciated. Will be nice to be able to have a car that don't rev itself!!

Car is a 1998 1.4 SOHC Honda Civic MB2 (cable throttle)

Thanks

 

[turbonutter69]

Hey everyone, right i've had this problem for about a year now. All started when the wading inside my old backbox fell apart and blocked the exhaust causing it the gases to come back into the cat and engine. During the time of limping home, gettin overtaken on hills by lorries, the idle once engine is warm goes from 800rpm to 1500rpm constantly.

I have done the obvious and got another icv and still had the same problem. I have changed the throttle body with no effect also.

We discovered the icv was having problems knowing whether to be open or closed. Hence this jumping revs.

Does anyone know of any sensors on a Honda Civic that may cause this. I am gonna get a new Intake Air Temp Sensor to try and maybe a coolant temp sensor.

It only does this once the engine has warmed up telling me it isn't the icv but something that talks to the icv. Something that may have got damaged by the exhaust gases, lambda sensor and cat reads fine as passed mot.

Oh yeah other thing is, I had the icv blanked where the air and water runs through and it didn't idle at all which is what was expected so again i dont think its the icv.

Other things done -
Changed the whole head and relevant gaskets. Still on now.
Changed intake manifold and throttle body. Still on now.
Resistances have been checked on sensors.
Dizzy n rotor arm have been replaced.
HT Leads have been replaced.
Spark plugs have been replaced.
ICV has been replaced.

All ideas will be appreciated. Will be nice to be able to have a car that don't rev itself!!

Car is a 1998 1.4 SOHC Honda Civic MB2 (cable throttle)

Thanks

Hi there mate this baffled me a bit so I did a bit of research. Now I don't know exactly what it is but it is some on the vacuum side of your engine. It's exactly what you've described with the exhaust blowing back up. It's a disturbance in the vacuum system somewhere.... Hope this helps mate.

 

[obi_waynne]

Vaccum leaks are easyish to find if you listen to the engine when revving and you will notice a hissing noise.

Have you replaced the MAF/Air temp sensor? (Might be part of what you've already replaced but i've seen some people replace everything and use the old sensor,cable which had the fault!)

Unplug and replug everything around the ECU, Air Sensor and Lambda. You might be lucky with it just being a bad connection.

My hunch though is that pressure built up in the crank case and blew a vacuum hose which is now leaking. (Again remove and refit at both ends to ensure a tight fit!)

 

[pgarner]

smoke kits are avalible to check for vac leaks

 

[prevtec]

the brother had the same problem with his punto, reving up and down when warm
all i done was threw injector cleaner, and a small drop of deisel 1 euro, and fill the car with petrol, then hit the road and screw it and i mean limiter in every gear

do this when its warmed up for 20 mins, dont worry its a honda and let us know mate whats what, this is very cheap to have a go at it, so have a go with that

 

[wezzel98765]

Saying that, I just noticed this on my clio, usually only when on a cold start though :s

Once I have driven it a little bit it stops doing this, I thought it was the sound the induction kit was making, so I took that off, and it still kept doing it

Wayyne, when shall I come over for you to check ?

haha

 

[nrvmotorsport]

Have managed to sort this problem, it was down to the dizzy being about a degree out and a slight split in one of the vacuum hoses. Still have slight problem of over idling when no lights and heater ona nd under idling when there on lol

Thanks those that advised on possible causes

 

[obi_waynne]

Nearly there then. 1 degree out eh - it doesn't take much does it!

Is the alternator charging properly?