I've been having a long term issue with my car. After I had the car looked at by a "pro" (in May), it started to run a little rough at idle. I assumed it was just the new "normal". But after finishing my most recent project, I thought that sitting for 7 weeks+ was the issue.

So this weekend I checked vacuum lines and checked the plugs. The plugs were a little dirty but nothing bad. I checked the distributor and it was a little rough (so I cleaned it up). Obviously to get the distributor cap off, I had to remove the air filter box.

But in the process of putting things back together, I noticed that the air intake hose was completely missing. I think because it was not there when I started, I didn't even notice that it was gone. I cannot find it for the life of me (and haven't had a reason to take it off of the car in months).

So I'm guessing when I had the car looked at, the hose was not put back into the car (they must've taken off the air filter box).

I was looking at the bottom of the air filter box, and I noticed that there is a plug that goes into the vacuum line port. It wasn't plugged in and I knew that in order to remove the air filter box, I would have had to disconnect this plug. And if I hadn't disconnected this plug, it would've broken something. So I'm 100% certain I didn't remove it, and that it was not connected.


So I have a question. Would these issues potentially cause a rough idle?

Here is link to the plug I am talking about. It is on the bottom of the air filter box.




Here is the air intake I'm talking about (I found one at a pnp)



Sorry if this seems disjointed, I'm not sure what the names of the parts are.

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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course.

In my perpetual chase of a vacuum leak, I ran into a bit of an odd situation. My brakes seemed to go out the other night, as I was driving down out of my driveway.

It didn't happen again, but it almost felt like when you are in neutral and the E brake isn't working properly, but I was in reverse and had to put extra pressure on the brakes to slow the car down.

Once i got out the driveway I pumped the brakes to see if something was wrong, but it acted normal.

Fast forward to today, and I've tinkered a bit with the car. I took the brake vacuum hose off, and it has good suction (the car dies if I don't plug the hose). I put the hose back on and the brakes seem to be normal. I ran a few tests to see if the brake booster or check valve were the issue, and it doesn't appear they are (the brake pedal is solid, and doesn't sink to the floor or rise up..i.e., I don't think it's losing vacuum).

However, I notice that the car runs rougher whenever I pump the brake, like maybe that is the location of the vacuum leak. I meant to do a water test earlier (but as usual, life got in the way).


my question is, before i do the water test, is a rough idle that is made worse by pumping the brake pedal, maybe sound like a vacuum leak in the vacuum line for the brake?
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course.

Sounds like you are on the right track, with the brake vacuum. If the check valve is good, it may be a seal in the brake cannister.
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Keeping it running is better than buying new

A missing air intake line will not cause rough idle. A disconnected vacuum line will.
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Keeping it running is better than buying new

Thanks.

It ran fine yesterday, but today is ran rough. Shaking the engine (not a ton, but enough that the steering wheel vibrates).

Does anyone have an easily readable vacuum line diagram?
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course.

The vacuum lines are not too hard to follow in your car. There are a few on the front of the manifold, one of which goes to the SAS valve, connected to the side of the radiator.

Remove the throttle body cover and take a look at the vacuum tree. Those lines go to the PCV and air box. Sometimes, the unused vacuum port covers fall off due to age. Try to wiggle the vacuum tree, if it moves, you may need a new one with gasket.

Take a good look at the Idle control motor air lines. No cracks is good.
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Keeping it running is better than buying new

first picture is secondary air pump solenoid valve

I’m not sure what the plug is for.

The missing air hoses might account for the rough idle as air flow into the air filter box and subsequently into the engine are most likely changed and could throw off the air-fuel mix??
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Will I buy another Volvo??? We'll see....