I'm new here since I recently purchased a 2010 Volvo S40 (155,0000) and thought maybe you guys can help me out. I have a check engine light for a misfire in my fourth cylinder. I replaced the spark plugs about two weeks ago, i replaced the coil pack to cylinder 4, and still the light pops up. When i went to Autozone to check for codes, the computer had recommended that based on prior knowledge with my car and with the mileage, they recommended to replace Fuel injectors. My experience with working on cars is alright. I've worked on my car plenty of times but I've never worked on fuel injectors I guess my questions are

1. Is it dumb to try this myself? I've watched some videos on Youtube and the job doesn't seem too hard but I guess what I'm asking is, is there any rookie mistake that i can potentially do to ruin my car?
2. Can I just replace 1 injector (number 4) ? Or, do I or should I just replace them all?
3. The videos I have watched on Youtube are a Volvo T5 and S60. Can these videos apply to my S40?

Thanks a lot guys !
-Bryan from NY

 

Before replacing an injector or any more parts that you have not proven are bad - I would swap 2 injectors - swap #4 and #5 and see if the miss fire moves to #5. It is very rare to have a bad injector. Have you checked compression on this engine?

I would have done the same with the coil before replacing it also - at least you have a spare now.

 

also inspect the wire harness to the coils to make sure you don't have cracked connectors etc. More common on older models but still work a look. Also, if you haven't been doing so, do you next fill or two with brand name premium or drop in a can of Techron injector cleaner. Also try spraying around for a vacuum leak. You may have something around the injector or in the intake to the point where it may trigger a misfire code..

 

so I was actually going to do that with the coil pack (swap 4 with 3) but I was reading on Reddit Volvo sayin it’s almost always the ignition coil, so I went along with it. Didn’t think i could do the same for the fuel injectors. Thank you for that tip. And no I have not done a compression test, I could find out how to do one on YouTube !

 

I was confused where you said “do you next fill or two with brand name premium” as in go to a brand name has station and get premium gas ? And I was thinking of a fuel injector cleaner ! And what do you mean start spraying around for a vacuum leak ? Sorry

 

Remove spark plugs, screw compression tester in cyl1, spin engine over least 6 or 7 revolutions, take note of compression readings, move to cyl 2 and repeat for all. Readings should be close to each other somewhere between 150 -200 psi depending on the compression ratio. Important thing is they are all somewhat equal. If one or more is low, squirt a small amount of oil into the cylinder to help seal the piston rings - If #4 is still low you may have a burnt valve. If any are near 100 psi only - the cylinder is going to not fire, or will missfire - You need about 100 psi for combustion.

By a can of carb cleaner, install the nozzle - with the engine running spray the carb cleaner at areas that might have an air leak - between intake manifold and cylinder head( manifold gasket), injector seals, where vacuum lines terminate or connect to something, or anything connected to the intake manifold. Carb cleaner will change the idle speed - for only for a split second, the auto idle system will self correct the idle speed quickly.

We would have intake manifold gasket failures after doing valve jobs - if we let the machine shop do their normal finish on that surface and used the factory intake gasket. The aftermarket gaskets did not seem to have that problem.

 

yes, for your next fill up, go to a brand name like Shell, Mobil, Chevron etc and fill up with 93 premium. They put extra detergents in the full and after 1-2 tanks you'll get the benefits without doing anything more than paying a bit more at the pump.

+1 on hoonk - the compression test is best done on a warm engine and the target is 150 PSI + for a turbo engine (which has slightly lower compression) and 180+ for a naturally aspirated engine. Once you do that if you find one or more cylinders is off that target, you can do the "wet" test where you put a tablespoon or two of oil down the spark plug hole then repeat the test on that cylinder. Idea is, that oil is enough to help seal the rings - so if the compression is notably higher wet than dry, you have piston/ring issues. If the dry and wet PSIs are the same, then it points to a head or valve issue.