[Monkey Wrench]

Im pretty familiar with 80's and 90's volvos. with those there is a crankcase "flame trap" its in the hose between the crankcase vent and the intake manifold.
the dirty fumes pass through basically a piece of plastic full of tiny holes. they plug up , thus increasing crankcase pressure. I bought one cheap/ used and it was pushing the dipstick right out. the issue can also cause seals on the crank to blow out, If the rear main seal does blow out it requires engine or transmission removal..
so I pull the thing out wash it out well and use a little piece of copper wire or a welding tip cleaner will work to clean out all the little holes. .. or just replace it.

it sits pretty much top of the crankcase breather on a volvo, which is a little plastic box that's supposed to I guess let the oil drain back as it is captured. sometimes they can warp / crack . come loose and leak.

on really old ones it might just vent to the road, or on some from the later 60's , to the air cleaners.

I'm less familiar with the 944 and how the crankcase fumes are vented. is there a comparable flame trap?

if those oily crankcase fumes are routed through rubber hoses and such it may cause the hose to rot out in some spot you can't easily see. that can create an air leak past the mass airflow sensor so the computer doesn't account for that extra intake air. Its plumbed into the intake manifold, which has vacuum. That extra intake air that the computer isn't' aware of, upsets the air fuel mixture, probably causing poor idle, maybe flat out it is less of a percentage. some do a smoke test and pressurize the intake with smoke to look for leaks, maybe that would uncover an issue like that.

My 944 is early 85 non turbo. Id like to learn more about how such issues may translate from Volvo's to the 944.. I suspect our older engines may need some attention in the area?

a quick and dirty old trick is to remove the oil filler cap usually on the rocker cover, with engine idling. see if it is sucking in or trying to push fumes out, the theory is a good engine will have some suction whereas a worn engine may be trying to push the fumes out. Im not sure if that is valid for a 944 it's just pretty general check Id do if looking to buy a car and not able to use wrenches, Id pull the dipstick to see if the oil is dirty too. with the cap off I 'd flip it over and check for any milky residue indicating a head gasket leak. you might note differences if you do that on a recently rebuilt motor compared to a old worn engine.

with the 1988 Volvo that was pushing it's dipstick out, the repair is 0 cost, just clean the flame trap. I think the previous owner didn't know that and likely pulled the car from use and it sat... I fixed that and might resurrect the thing, I bought it for parts, 400 bucks. broken windshiled but I got one, the headliners always fall down too, which it did and they are a PITA to change. The rest of it is pretty decent. I love those cars because they are really good workhorses, easy to fix, unchanged for quite a long run. Ive owned lots of them because I learned how to fix them, The porsche has a lot of similarities , all bosche stuff. The engine blocks and cranks were really strong so they can be re- bored. I re-bored my 122's 1800 to 2 litres, balanced it polished the ports, hotter cam , it goes like crazy now but looks OEM except for the big valve head from a later engine.
balancing that engine made a world of difference, now at the redline it sounds happy, way less vibration. I dont know how well the porsch is balanced. I suspect it would be more refined. I often wonder if you just take a stock one and balance it professionally during any rebuilding if it would make as much difference. I think the ports are already pretty smooth.. of course you can go further with the help of people that work on race engines.

The Porsch of course has an aluminum block, you can't just punch it out so easy, but it is lighter sort of higher performance I guess but the redline isn't any higher. way better at cornering. way cooler looking. not so great on rough dirt roads and in the snow.

The 240's have a super short turning circle , are easy to get in and out of , you sit upright. I never bought turbos. more power , but more stuff to fix. They often call them swedish bricks because they are square and boxy, and handle like a brick ;-)

like the porsch e the later 740's were completely redesigned with turbo, intercoolers, made way way more power, but also more crowded, more complicated. like the 944S it is similar looking to the cars they evolved from, but completely different.
all the later Volvo cars got overcomplicated in my opinion, once they started adding a zillion unnecessary wires, i got disinterested in anything made by Volvo. I dont want to own a car that will send me back to the dealer by generating cryptic codes.. I want one I can maintain by myself and understand so the 944 is a good fit for me. i like that mine is galvanized and not all rusty as a result.