Another High Idle revving thread

[Asura]

Hello guys, as the title says, may car idles high, and hard, like 4000+ rpms.
I also do know there are a lot of previous threads been going on about it and I have been through them, along with numerous searches on google, to no avail. Almost 90% of all the threads start with the problem, but never end in a solution, they just die, noone concluding in the actual fix.

But OK, here is my case:

I have replaced my '97 1.1 with a 1.6 NFZ engine at a point where the 1.1 had no more hope. I discovered that the 1.6 had also a blown head gasket, which is now replaced.

The engine runs quite OK without ICV connected! which excludes leaks. When I connect the ICV it shoots up to 4000rpm after seconds .
The actual problem is that the ICV opens up to much when running, it is not stuck. I can actually see this happening with another loose ICV...

What I have done/replaced, but problem remained:
- another throttle body, along with TPS
- another coolant TEMP sensor
- another ICV
- taken of whole intake and put it back for inspections of warped stuff or whatever
- another crankshaft sensor
- another ECU

O2 sensor should be OK, not really old.
MAP sensor should be OK, according to place I got it from, also without MAP sensor connected is stops running immediately.
Electrical circuits checked on breaks and resistance, nothing came up.

Does anyone have another idea or has had exactly the same problem that can cause the ECU to open up the ICV like this?

Thanks alot in advance!, Rick

[Asura]

Noone?

[MartinObviously]

If it's cheap Ebay style ICV, then I can pretty much gaurantee it's that.

The ECU will be seeing 4000rpm and should be requesting the ICV to close.

Unless the TPS is faulty, if it thinks the throttle body isn't fully closed the ICV is "disabled".

Leave everything plugged in, except the TPS and start it up.

You really need a good computer (Snap on or a copy of diagbox) to monitor what the sensors are doing in real time. Chasing faults like this will be a nightmare.

[SpijkerVTS]

Ive just learnt that when you fit the icv you should cycle the ignition 3 times to get it to set itself, you can also wind them in and out <br><br>Sent from my SM-G975F using Tapatalk<br><br>

[MartinObviously]

Originally Posted by SpijkerVTS

Ive just learnt that when you fit the icv you should cycle the ignition 3 times to get it to set itself, you can also wind them in and out <br><br>Sent from my SM-G975F using Tapatalk<br><br>

You don't need to cycle the ignition, that's a myth.

Fit it, start the car and immediately drive it.

[dturbo]

I've had similar issues when the TPS died. I agree with Martin, it's practically impossible to figure out what is happening without diagnostics. You can get Lexia on ebay for about 35 quid. If you have an old XP laptop you're set. It's really good. I have a 2000 VTS and get good info from it, my son's 2003 1.1 gets even more data, lots more detail.

I would strongly advise you go this route, it's less than the cost of a sensor. FYI you should be able to drive the car fine without the ICV plugged in, as long as you unplug it when the car is idling normally (best if done when the engine is warm). If it still misbehaves with the ICV unplugged it must be something else.

[Asura]

Thanks for your replies!

Originally Posted by MartinObviously

If it's cheap Ebay style ICV, then I can pretty much gaurantee it's that.

The ECU will be seeing 4000rpm and should be requesting the ICV to close.

Unless the TPS is faulty, if it thinks the throttle body isn't fully closed the ICV is "disabled".

Leave everything plugged in, except the TPS and start it up.

You really need a good computer (Snap on or a copy of diagbox) to monitor what the sensors are doing in real time. Chasing faults like this will be a nightmare.

Pity I dont have any fancy program at hand. Indeed I am thinking of doing some diagnosis on it somewhere who can. This is the pre OBD2 system however, is is possible to read all the sensors on the older versions?

About the ICV, it is also that what I am thinking; I don't think it is the ICV istelf. I have got 2 genuine bosch ICVs, which both seem to work fine and are clean. Is it only the TPS that can cause the ICV to open so extremely? Since I have two TPS's which make no change, this can also not be a coincidence. Then I probably have to search for electrical values that may get lost through bad wires (although I checked them numerous times...).

I'm guessing the MAP & O2 can not cause this, but TPS & Coolant sensors can...

[Asura]

Originally Posted by dturbo

I've had similar issues when the TPS died. I agree with Martin, it's practically impossible to figure out what is happening without diagnostics. You can get Lexia on ebay for about 35 quid. If you have an old XP laptop you're set. It's really good. I have a 2000 VTS and get good info from it, my son's 2003 1.1 gets even more data, lots more detail.

I would strongly advise you go this route, it's less than the cost of a sensor. FYI you should be able to drive the car fine without the ICV plugged in, as long as you unplug it when the car is idling normally (best if done when the engine is warm). If it still misbehaves with the ICV unplugged it must be something else.

It is indeed possible to drive with the ICV in closed position. Unfortunately it has also too high CO values which doesnt get it through MOT...

[Asura]

Originally Posted by MartinObviously

If it's cheap Ebay style ICV, then I can pretty much gaurantee it's that.

The ECU will be seeing 4000rpm and should be requesting the ICV to close.

Unless the TPS is faulty, if it thinks the throttle body isn't fully closed the ICV is "disabled".

Leave everything plugged in, except the TPS and start it up.

You really need a good computer (Snap on or a copy of diagbox) to monitor what the sensors are doing in real time. Chasing faults like this will be a nightmare.

Well I think I actually fixed it. Certainly along with your information. I was also suspecting the TPS, although I replaced it. But I did replug the connections for the engine swap.

I discovered that the plug I used was faulty, through measuring resistances directly from TPS and from TPS through the wires. Through the wires, the TPS resistances decreased! Pin connections were correct, but the plug was guiding electricity through the plastic . So I took it off and put the wires directly in the female connector, stared and the ICV reacted directly different, but the way it is supposed to.

I have been dealing with this problem for almost a month, replacing and watching wiring diagrams for errors. All was connected fine, but only for that crappy plug.

For the ones that have the same problem on idle, check everything on the TPS! TPSes dont die that easy, where many of us change it without improvements, usually its just in the connections...