s80 slow start
 

Begining at low temperatures and sitting all night at below 5°C my s80 starts slow. Like you see in the video below, it will start with no problem but the engine hangs at 700rpm for a few seconds and only then it will start up the electricity and revs a little harder (which should be normal from the begining).
Readings from VIDA show no errors, glow plugs were changed last year, car starts normally when warm, battery was changed last year, fuel filter 10.000km ago with OEM, EGR and throttle body cleaned. I have no slightest clue what could be wrong.

There's another problem when engine is warm (if that issue is somehow connected to this one). There's pretty noticeable rough idle when stopped and also RPMs fluctuate when coming to a stop. Interesting here is that rough idle at stop dissapears when I turn ON the AC or steer the wheels (put a load on the engine).

Volvo s80 2.4D M66 2009 (D5244T5) @360.000 km

Videos showing slow start:
https://www.youtube.com/watch?v=NIP6n9P7DSA

https://www.youtube.com/watch?v=jSIj2-B81Ts

Doesn’t seem slow to me. I’d say that was actually quite normal in colder weather.

You do realise that when you press the start button, the car doesn’t start instantly? The car won’t start until the heater plugs are warm enough. This is why there’s a delay from pressing the start button before the car actually fires.

That's not the case. I'm aware of the glow plugs delay, but if you look at the video, you'll see the delay after the engine turns. Yesterday I've open the oil fill cap and discovered the popping sound, so I think I've got a vacuum leak. This is regarding the warm engine problem (rough idle), but I don't think a vacuum leak has anything to do with the cold start problem?

I've read your post about popping sound back in Jan 18th, 2020 (D5 popping sound). Did you sort that out?

No, I never bothered with it. It won’t have anything to do with starting. The euro 4/euro 5 engines have a different vacuum system… they still have one, but its not the same as the euro 3.

As you’ve cleaned the EGR & replaced the fuel filter, then you may need to test the injectors by doing a leak back test. They can cause a lumpy idle.

What about the alternator itself? Maybe you have an issue with that, or the auxiliary belt is old & could be slipping.

I'm familiar with the euro 3 vacuum system as I had to replace the vacuum lower engine mounts back on my s60. I'll do the leak back test tomorrow and report back.

As for the alternator - it charges the battery @14V so that should be good and belt was replaced 60.000 km ago.

This is probably nothing - but it seems odd to me to press the start button so lightly and leave the engine to fire. I tend to press and hold the start button until it starts. Like I say probably nothing, just seems odd to me. Like if you were twisting a key, you'd twist they key until it starts and then release. You wouldn't just twist the key all the way round and release as soon as you met the stop.

You tend to do wrong, then. The starting system in these cars is fully capable of determining when the engine has started, so all you should do is a quick press, and it will take care of the rest.

You refer to old cars, where it was up to the driver to understand when the engine had started. And also, for diesels, it was up to the driver to observe the duration of glowing, and not turn to start until glowing was completed.

The only time you need to keep the button pressed to start is in emergencies, like if the clutch sensor on a car with manual gearbox isn't working. Then you have to confirm that it's OK to start by keeping the button pressed until the engine starts.

My car doesn’t have vacuum mounts. I’ve checked & can’t see any vacuum pipes going to any mounts.

I don’t think euro 4 P3’s have vacuum mounts, apart from the XC90.

My Dad’s V70 P3 is the same - No vacuum mounts.

So I want to get back to this as I resolved some things.

The "slow start" problem was due to an old/lazy starter motor. I've changed the unit with aftermarket Bosch and also replaced the battery and now car starts like a champ.

Rough idle problem went away when I added 2x 1liter (two separate times) of Antigrippante 25 additive in the tank when there was only 10liter of diesel in it. Inspecting the injector return pipe made me realized we have bad diesel in my country as there were a lot of rusty pieces in it - meaning there's water in it.