Surging idle

[Jimmyac28]

I got the car as a project with a bad head gasket, when I got it I turned it on at it had a surging idle but I didn't think of anything since it had a bad head gasket anyway. The car is a 1984 325e

I replaced the head with a rebuilt 323i head, 325i intake manifold, 325i throttle body, replaced the head gasket, water pump, timing belt and timing belt tensioner. I finished installing everything today, turned the car on and it still has a surging idle.

What could be causing the surging idle?

Here is a video of the problem

https://youtu.be/mhuJZvBvCX8

[tiger_e30]

I got the car as a project with a bad head gasket, when I got it I turned it on at it had a surging idle but I didn't think of anything since it had a bad head gasket anyway. The car is a 1984 325e

I replaced the head with a rebuilt 323i head, 325i intake manifold, 325i throttle body, replaced the head gasket, water pump, timing belt and timing belt tensioner. I finished installing everything today, turned the car on and it still has a surging idle.

What could be causing the surging idle?

Have you cleaned your idle control valve

[Jimmyac28]

Have you cleaned your idle control valve

I have not cleaned it yet. I just took added a video of the issue

[tiger_e30]

I have not cleaned it yet. I just took added a video of the issue

I'd pop it out and clean it. Should only take 20 min and fixed my idle problems last week

[Jimmyac28]

I'd pop it out and clean it. Should only take 20 min and fixed my idle problems last week

I just cleaned the ICV and rechecked every vacuum hose and everything is tight but it still does the same thing. What else could it be?

[e30davie]

Engines only rev up if they get more air, you got an issue somewhere that is letting more air in than it should.

Unplug the ICV and see what happens.

[Jimmyac28]

Engines only rev up if they get more air, you got an issue somewhere that is letting more air in than it should.

Unplug the ICV and see what happens.

I unplugged it and nothing happened

[TobyB]

Now squeeze your boot hard and see it it's cracked.

t

[Jimmyac28]

It's not cracked, I checked it before I installed it. Like I said the idle was surging before I I started taking the top end off to replace the head gasket. Could it be the idle control module that is bad? When I unplug the ICV nothing changes also smells like it's running rich

[Jimmyac28]

Any suggestions

[Supratreo]

Could be air in the cooling system.

[Jimmyac28]

Could be air in the cooling system.

I bleed the cooling system already

[ahlem]

drill a 1/8" hole in a dime and put it in the ICV hose to restrict the air flow and see if that makes a difference. If so, your ICV or that circuitry is the issue.

[Jimmyac28]

drill a 1/8" hole in a dime and put it in the ICV hose to restrict the air flow and see if that makes a difference. If so, your ICV or that circuitry is the issue.

Which side of the ICV?

[SteveO]

Which side of the ICV?

Shouldnt matter but I had a similar issue and the temp fix was to put that penny with a hole in it on the downstream side of the icv. The penny fits perfectly in there and will not be able to go anywhere.

Edit/fun fact: since I live in canada and the penny is not in circulation anymore i had to use a nickel. It worked the same just cost me a little bit more. I think it had some issues at cold starts, had to keep the throttle open but that was only when it was -25°C in Prince George. If I remember correctly I used a smaller hole than 1/4" though as that was idling a little bit too high once it was warmed up. 7/32" I think