2008 S60 2.5T, Misfires on cylinders 1 and 3

professorsunshine · Post by **professorsunshine** » 20 May 2025, 22:23

I bought a Volvo s60 not too long ago from facebook marketplace. The original owner said that a spark plug popped out of the center cylinder while on the highway. After a helicoil and a new coil pack the engine still isn;t running right. Here's what I've done so far.

-tested wiring going to all coils, good
-tested all coils, good
-tested all spark plugs, good
-tested compression on all cylinders, good
-cleaned all injectors with brake clean and 9 volt battery, all good
-retimed the engine according to this video (

after all of that work, the engine runs almost exactly the same as it did before, very shakey like it's out a cylinder or 2. I'm really thinking it may be a bad cam/crank sensor or vvt solenoid. any easy way to test those? If anyone has some idea of what's wrong with my engine I'd greatly appriciate it.

Post by **jonesg** » 21 May 2025, 09:17

I would want to put vida on it.
Does it have a CEL , any codes.?

Vova585 · Post by **Vova585** » 21 May 2025, 09:23

You mentioning "misfire on 1 and 3" in title, do you have constant codes for them or your scanner shows "misfire count"? Have you tried to move spark coil, plug, injector to the 5 cylinder(furthest away from problem area and possibly "known good"). Do you have a borescope to look into to 1st and 3rd cylinder to see if there no mechanical damage to the walls? OK, assuming 3rd spark plug popped away,why then 1st is giving issues? Any chance there is thread repair coil in cylinder 1 as well? Before you re-timmed the engine, we're you able to check marks? We're they ok or how off they were? If they were off by a lot, I would take articulated borescope and would look at valves.
Are we sure all the plugs are correct for this engine? It is possible that someone "was there" before you and it resulted in damage to begin with.

Post by **cn90** » 21 May 2025, 09:48

Coils are difficult to test when COLD.
Very often they manifest it when HOT.

Best is to get a few used coils at junk yard or eBay.
Or buy 2 new coils at let's say FCPEuro for testing.

professorsunshine · Post by **professorsunshine** » 21 May 2025, 20:23

I just went out and re-read the codes. Here's a screencap (
P0303-cylinder 3, misfire detected
P0301-cylinder 1, misfire detected
P0300- random/multiple cylinders, misfire detected.
Those 3, repeated twice.

I have 2 coils that I bought for testing, 1 volvo OEM coil and 1 cheap aftermarket one. While warm, the only cylinder that doesn't change how the engine runs when unplugged is the middle cylinder, the one with the helicoil. Niether new coil makes the engine run any differently. The cylinder does have good compression, roughly same compression as the other cylinders.

I didn't take any pictures or pay attention to how it was timed before retiming it myself, but after retiming it runs precicely the same as it did, same ECU codes and all. Its possible that me and the last guy could have both done it incorectly in the same way, I liked the vid I followed in the OP.

While I'm at it, I'll say that The engine can stay running and will drive the car, it doesn;t overheat whatsoever, so the head gasket is likely just fine. Thank you so much for the quick replies, I love this forum.

Vova585 · Post by **Vova585** » 21 May 2025, 22:22

Possible steps: in case you scanner is equipped with graphical view misfire count you can concentrate on cylinder 3 and see if the problem is persistent or it intermittently works. You can try to move injector from 3 to 5 and see if any changes. As silly as it sounds- make sure that wires to the coils are properly connected. There are plenty of youtube videos for reference. If despite swaperu of coil, injector, plug(one at a time) from 3 to 5 you are getting similar results i would try to find proper electrical diagram and see what is common between 1 and 3. Maybe they share ground(would make sure to load test with 4amp light) for coils(believe coils are 3 wore design so positive,ground and control signal by logic(so load test positive end as well). Also see if any common wires between 1&3 injector(likely ground controlled). If you have aQatarccess to smog machine it might not be a bad idea to see if you have some major air leak. If that all does not answer anything you can rent cylinder leak down tester(or buy one from otc they are awesome) and test 1&3

On the other note. If you are feeling that it becomes too much and you need answer asap, I would look around for a reputable mobile mechanic with advanced diagnostic equipment. PICO like scope with several channels comes to mind.(injector, coil, pressure transducer, relative compression test all can be performed within short period of time, but cost of equipment is not something that i would suggest for and an average diy(probably 6-7k for a kit and pressure transducer). Mechanic should have also subscription to all data and will be able to find all wiring diagrams quick. No shame in calling reinforcements(especially if one can come to conclusion it might be my ecu causing issues..)

XC70Rider · Post by **XC70Rider** » 22 May 2025, 21:22

As mentioned your IGN coil connectors could be misconnected. With the coils facing in different directions some are close to the same length from the harness. I mixed up 2 coils when I first changed the spark plugs a decade ago. I now have colored tape on the pigtails so
i don't ever do it again.

professorsunshine · Post by **professorsunshine** » 22 May 2025, 21:48

I used this doc (https://www.davebarton.com/pdf/5Cylinde ... sGuide.pdf) to double check that my wiring was all good. All of the coils are plugged into the correct plug.

When cleaning the injectors I mixed them all up and put them back in randomly. Although I suppose there is a chance, I don't think the injectors for cylinders 1 and 3 both ended up back in their respective place. When cleaning them, they all tested out good, and I can hear all of them firing, even the one for cylinder 3, with a stethoscope.

while fiddling arond I realized that the exaust smelled a whole lot like raw fuel, even after the car was warm. I tried unplugging cylinder 3's injector and that smell went away a little bit.

XC70Rider · Post by **XC70Rider** » 22 May 2025, 22:16

Did you have all the ground bolts mounted onto the IGN coils? Forgetting to mount those bolts is another mistake I made years back.

professorsunshine · Post by **professorsunshine** » 23 May 2025, 00:35

I did all of these tests with the coils and ground points bolted tight to the cam cover. I was hoping that it would be just a ground problem when I bought the car but despite the insulation cracking and coming off, the ground is fine.