Idle with no idle control system

[Carbuilder]

Here is a bit of a head-scratcher.

I've put about 1,000 kms on my car since getting it. It runs great and idles fine. Maybe a touch high, just under 900 RPM. With the A/C switched on it drops about 100 RPM, but idles steady under any condition; so far anyways.

Justin from https://wellsauto.ca came over a while ago to check out the car. The guy really knows his stuff. He spent a long time showing me the things that had been changed on the car and taught me so much about it. He showed me what is in the compartment behind the driver; the upper one:

70889

He looked puzzled and said there is supposed to be an idle control computer there. You can see the connectors that are taped off. With the engine running he pulled off this connector:

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No change to how the engine was idling. He didn't know how the idle was being controlled. He took it for a drive and said it was a very good car. And he said the idle system had obviously been tampered with, but since it is all working fine, to leave it alone. So I am. I think he said it had a Volvo intake if that makes any difference.

Rick
17091

[David T]

Here is a bit of a head-scratcher.

I've put about 1,000 kms on my car since getting it. It runs great and idles fine. Maybe a touch high, just under 900 RPM. With the A/C switched on it drops about 100 RPM, but idles steady under any condition; so far anyways.

Justin from https://wellsauto.ca came over a while ago to check out the car. The guy really knows his stuff. He spent a long time showing me the things that had been changed on the car and taught me so much about it. He showed me what is in the compartment behind the driver; the upper one:

70889

He looked puzzled and said there is supposed to be an idle control computer there. You can see the connectors that are taped off. With the engine running he pulled off this connector:

70890

No change to how the engine was idling. He didn't know how the idle was being controlled. He took it for a drive and said it was a very good car. And he said the idle system had obviously been tampered with, but since it is all working fine, to leave it alone. So I am. I think he said it had a Volvo intake if that makes any difference.

Rick
17091

Your friend is correct, the idle ECU is missing. If you are happy with the way the car is running then leave it alone but the car is supposed to have it and if it was working it would hold the idle steady no matter if the A/C is running or not. Someone in the past probably could not get the idle motor to work right so they removed the idle ECU and fiddled with the idle speed and air adjustments to get it to idle without it. BTW the idle speed is 750 with the idle ECU but without it they increased the idle speed so it would idle "happy". If you have a 5 speed, the higher idle is necessary without the idle ECU so it doesn't stall when you start out in 1st. Do you hear the frequency valve buzzing? That system may have been tampered with also.

[WHO1DMC]

https://youtu.be/3wUrEkepSfU?si=Vfm8IFtTIfni3k93

Maybe this has been done. It bypasses the idle motor.



Dave B.

[AugustneverEnds]

https://youtu.be/3wUrEkepSfU?si=Vfm8IFtTIfni3k93

Maybe this has been done. It bypasses the idle motor.



Dave B.

Twelve years of owning and wrenching and still learning! Thanks for posting

[Timeless]

Rick, if you need an idle ECU I have one available.

[Carbuilder]

Rick, if you need an idle ECU I have one available.

I appreciate that, but for now I'm going with Justin's suggestion of leaving well enough alone. Not sure why it was removed in the past, so might be headed down a rabbit-hole if I start changing it. If it starts acting up seriously, then I'll look into that.

Meanwhile, I don't have 2 of the 3 plugs shown in the video. The holes have been filled in with sealant of some sort. I think Justin said it was a Volvo manifold; why it was changed.....no idea. The 2nd owner (the one I bought it from) said he didn't change anything like that.

Rick

70895

[82DMC12]

I appreciate that, but for now I'm going with Justin's suggestion of leaving well enough alone. Not sure why it was removed in the past, so might be headed down a rabbit-hole if I start changing it. If it starts acting up seriously, then I'll look into that.

Meanwhile, I don't have 2 of the 3 plugs shown in the video. The holes have been filled in with sealant of some sort. I think Justin said it was a Volvo manifold; why it was changed.....no idea. The 2nd owner (the one I bought it from) said he didn't change anything like that.

Rick

70895

The "plugs" are actually sheer-off bolts. The bolts are used to balance the air volume to each side of the intake. The third screw that you have allows the balance screws to function in the first place. When the idle ECU is used in factory configuration, the flathead screw should be screwed down snug which blocks the flow of air to the next two sheer-off screws.

Our assumption here is that the flat head screw is open and allowing idle air into the intake (rather than the ECU controlling the idle motor with the black plug on it in your earlier photo). Then the two sheer screws are set however the previous owner wanted them. Not sure why they would be sheered off though if they are actually in use!

If you want to leave well enough alone... leave them alone! Ha!

[Carbuilder]

The "plugs" are actually sheer-off bolts.

If they are sheer-off bolts, then they are sheared off well below the surface and then filled with sealant; it is soft stuff. Maybe they are grub-screws or set-screws, fairly short, and adjusted and then sealed.

[dn010]

Those screws taper from the head down pretty thin and can easily break. The threads don't start until lower in the hole. If it's running fine - leave it alone. If you have problems you can remove whatever crap the hole is stuffed with and cut a line into the brass where the head broke off and use a flathead to adjust (or remove/replace). I've been there/done.