2004 S60 T Exhaust Pulsing at Idle, misfiring erratically around 0.3Hz

gerruta · Post by **gerruta** » 10 Feb 2020, 02:28

Good morning Volvo friends. I apologize in advance in case this has been asked before, but I wasn't able to find anything similar through the search feature. However, it may be because english is not my main language and I'm not too savvy on technical car words.

My exhaust, well, the whole car, seems to be randomly "pulsing" (?) at idle. I have attached a video to show you how that sounds like. You can feel it from the interior as well, when you are in idle, randomly, a very faint "thunk" will sound, I believe it's the same time when the exhaust does these pops.

The car is a 2004 s60 2.5T AWD. Has 200.000KM. I just changed the spark plugs, engine oil and filters and air and fuel filters.

Please ask for any extra information you need.

Video: https://photos.app.goo.gl/rsEP55h4nuSCrnCb6

Thank you!

Post by **oragex** » 10 Feb 2020, 06:49

Interesting, to me it sounds like a small misfire. Maybe look at the engine at idle, see if it 'shakes' a little. Also make sure to use the correct spark plugs for these engines, I think it's Bosch who makes them Here's how to detect a fault ignition coil www.youtube.com/watch?v=fnYUQh23p7Q

Post by **abscate** » 10 Feb 2020, 07:04

How old are the ignition coils? You have five on these engines, one for each cylinder.

They last from 200-300k km, so it is bit early for them to go, but you could buy a set of five if you know you will keep the car, and save the good ones as spares.

gerruta · Post by **gerruta** » 10 Feb 2020, 07:08

Thank you, I love that guy, lots of volvo knowledge. I just changed the plugs a couple days ago, when I detected the issue, it had been going for some time but I wanted to get it fixed.

Interestingly, one of the housings of the spark plugs, 2nd one, was full of carbon deposits. All of the other ones were sparkling clean. See this picture:

https://photos.app.goo.gl/XXhiom27HHZyZadK6

The one on the left is the dirty one, all of the other ones were as clean as the hole on the right. I have also checked to see if the coil was bad, with the same method, unplugging it with the engine running and seeing if nothing happens, and the coil is working. I did not clean the carbon when changing the coils as I feared that it could fall into the engine through the spark plug hole and I don't know whether that would be really bad.

I don't know if the dirty housing has anything to do with this problem, but it could be that that second plug is causing some small misfires? The revs are normal, and don't move crazy like when the engine has an actual misfire. And yes, while it's popping, you can feel the engine shake and in the interior, the steering wheel, etc, ever so slightly.

EDIT: I was typing this message while getting the new one: I have had this car since 150k KM, now it's 200K KM. I have not replaced the coils and to my knowledge neither has the previous owner. I'm not getting any signs of big misfires apart from this. Also, here's a picture of the plug I took from the 2nd coil: https://photos.app.goo.gl/N37qEPqp7xD71Ce6A vs one in one of the other cylinders.

Thanks again for your help!

Post by **abscate** » 10 Feb 2020, 07:20

If you want to stay on the 'cheap' just buy one spare coil and move it from cylinder to cylinder to see if the popping goes away.

If it is intermittant, then pulling the connector does not help the diagnosis, unless you can hear the pop over a constant missing cylinder.

gerruta · Post by **gerruta** » 10 Feb 2020, 07:26

That could be a great idea to at least help diagnose the problem, and I also don't have a big budget as a 23y/o student at the moment. Thank you. Do you have any idea why that particular 2nd cylinder was so dirty, and the other four were clean as new?

Gerardo

Post by **abscate** » 10 Feb 2020, 07:42

The 2 and 3 cylinder sit near the PCV pipe and can pick up some oil from the top of the engine. The spark plug could also have been bit loose, but that is usually noisy, too.

If you know someone else with a Volvo, borrow a coil from their car to run that test. There should be a few professors with Volvos

Post by **oragex** » 10 Feb 2020, 10:18

Exactly, not just from the PCV hose but also from leaking oil refill cap seal - you can even see on the first pic right on the 'canyon' above the dirty cylinder hole, oil has been sitting there for a while. The rubber insulators on the coils actually don't seal the cylinder hole so oil leaking from the PCV hose or from the oil cap seal easily find access there. Also good to know not to let the hood open in rain for the same reason - and also not to wash the top of the engine with water either (I did so)

gerruta · Post by **gerruta** » 10 Feb 2020, 14:46

Thank you all for the advice. I'll buy a coil and swap it out with the different ones and see if it goes away. I'll also try cleaning that hole as best I can without dropping stuff into my engine. The PCV part scares me, I believe I have got a problem with that, as the car fails that "sucking a glove through the oil hole" test, and I also have a small oil leak near around the part where I've read it would be if I had a problem with the PCV. However, I don't know if it's worth it for me to get it repaired. I believe that it would be at least 800€ to do so, on a 2500€ car (that I love).

I think that my plan is to run it until it explodes, with basic maintenance and whatever I can do to it.

Post by **abscate** » 11 Feb 2020, 05:01

Does the glove inflate or just stay limp?

If it inflates, you should use the interim catch can solution until you can fix it, so you don’t blow seals

Cam seals 100 EU
Main engine seal. 1000 EU