Bad idle B18F 1989

[Daan480]

Hello everyone,

I am having problems with my idle rpm for a few years now. The rpm is alternating between 600 and 1200 when idling. I have already tried replacing the idle control valve and this sometimes solves the problem temporarly but then after a while it fails again.

Today I removed the throttle position sensor because I saw people on the forum talking about oil in the sensor. This was the case for me, so I drained the oil out of the sensor and cleaned it and put it back. This however did not solve the problem.

I also saw people writing about 2 cylindrical connectors in the cable loom near the oil dip stick and when connected, the idle settings could be changed. I looked for these connectors but they are nowhere to be found. There is however a larger 4 pin connector near the dipstick but I do not know where this connector is for. I was thinking that maybe 2 of the 4 wires are used for the idle settings. I have tried
adding pictures of it but I can't seem to get it to work.
The connector has the following 4 wires:
- Brown
- Green with yellow
- Yellow
- Yellow with black

I have also tried swapping the idle control valve out again with one I had laying around, and now it idles at 1500 rpm. When I disconnect it then it starts alternating again between 600 and 1200, and then when I reconnect it again while it is still running, it stays alternating and does not go back to 1500 rpm.

Any suggestions on how to fix it and on what that 4 pin connector is used for would be amazing.

Thanks in advance!
Daan

[Keyz]

The tps (throttle position sensor) tells the computer what the position of the throttle is.
Then the iacv (idle air control valve) is adjusted depending the position of the tps.

If the tps is unplugged idle will be between 1200 and 1500 rpms.
Try to change the tps, it could have dead spots on its track.

[jamescarruthers]

When you put the throttle position sensor back did you set it's position up? That is key.

I don't think there is any wires to be joined up and affecting idle speed on an 89 car. It's a much simper set up.

[Keyz]

Yes, I forgot that point to mention the throttle position must be set inclined not straight, when you stand on front of the engine, the top of the tps must point towards you and the bottom must points towards the firewall. Thus when you turn the throttle the switch clicks

[Daan480]

I cannot really change the position of the throttle position sensor.
https://volvo-480-europe.org/forum/view ... hp?t=35760
If you scroll down in the above thread, you will see a picture of the same throttle position sensor as I have.

I have measured the resistance of the tps and when it is fully closed, the resistance between the most right pin and most left (if I remember correctly) was around 1100 Ohm and the resistance between the most right pin and the middle pin was infinite. When the throttle is fully open, it is the other way around. I remember reading somewhere that the resistance should be 0 Ohm or infinite. Not 1100 Ohm.

I have cleaned the throttle body as well and that did not make any difference. I think I am going to look for a new tps.

[royhedger]

I had a similar issue recently with high rpm and it hunting between 900 and 1500 rpm.
It was an air leak in the intake pipework.

Hope you get sorted soon.

[jamescarruthers]

I cannot really change the position of the throttle position sensor.
https://volvo-480-europe.org/forum/view ... hp?t=35760
If you scroll down in the above thread, you will see a picture of the same throttle position sensor as I have.

I have measured the resistance of the tps and when it is fully closed, the resistance between the most right pin and most left (if I remember correctly) was around 1100 Ohm and the resistance between the most right pin and the middle pin was infinite. When the throttle is fully open, it is the other way around. I remember reading somewhere that the resistance should be 0 Ohm or infinite. Not 1100 Ohm.

I have cleaned the throttle body as well and that did not make any difference. I think I am going to look for a new tps.

Isn't it on slotted holes on the car?

[Alan 480]

I cannot really change the position of the throttle position sensor.
https://volvo-480-europe.org/forum/view ... hp?t=35760
If you scroll down in the above thread, you will see a picture of the same throttle position sensor as I have.

I have measured the resistance of the tps and when it is fully closed, the resistance between the most right pin and most left (if I remember correctly) was around 1100 Ohm and the resistance between the most right pin and the middle pin was infinite. When the throttle is fully open, it is the other way around. I remember reading somewhere that the resistance should be 0 Ohm or infinite. Not 1100 Ohm.

I have cleaned the throttle body as well and that did not make any difference. I think I am going to look for a new tps.

Thats the image I posted and part of the issue was that the INTERNALS were getting filled with engine oil leaking down the throttle spindle, so I drilled a hole to let it out, not ideal, but it fixed the problem, know i should have fixed the oil passing into inlet, but drilling a hole and cleaning out excess oil from inlet bellows was much cheaper . . . .

[Daan480]

Isn't it on slotted holes on the car?

Nope, it only fits in one position. As far as I can see there is no way to adjust the position of the sensor.

Thats the image I posted and part of the issue was that the INTERNALS were getting filled with engine oil leaking down the throttle spindle, so I drilled a hole to let it out, not ideal, but it fixed the problem, know i should have fixed the oil passing into inlet, but drilling a hole and cleaning out excess oil from inlet bellows was much cheaper . . . .

I had hoped that your trick would solve my issue as well but sadly enough it did not. I think that the oil damaged the sensor already and I hope that replacing the sensor will fix the issue.

[Keyz]

What did you use to clean the sensor?
Brake cleaner?