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Discussion Starter · #1 ·
I had CEL P0303 - Cylinder 3 misfire in a 2006 S40 2.4i. I replaced the ignition coil and my wife's CEL went away for nearly a week, but now it is back. Any ideas?
 

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Three things are required for a combustion. Fuel/air, compression, and spark. Start with the cheap and work your way up. Coil and spark plug, fuel injector and fuel pressure in general, and compression. Swap the injector from #3 to a diff one, clear the code and see if the misfire follows where u swapped your injector to. If that doesnt work then do a leakdown and compression test but even then that can mislead.

I had the exact same problem on cyl #3 and it had the best compression! Turned out it was a head gasket fml. Since metal expands when it heats up it "filled" the gap that was in the head gasket and didnt let coolant drip in it while it was running but let it when it was off causing a misfire on startup

Whats your symptoms, miles, engine ect. Misfire on startup and it goes away, misfire while driving?
 

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Discussion Starter · #3 ·
She says it doesn't feel rough like when it started. It was obvious she was on 4/5 cylinders while we waited on the ignition coils to be shipped. Now we just have a CEL, and no noticeable symptoms. I did get a new air filter while NAPA had their 70% off sale, will replace that too, no idea how old this one is. The spark plugs were replaced by the Honda dealership I bought it from, so I somewhat doubt that is it, unless they didn't know something about Volvo, which wouldn't be too surprising.
 

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Its safest to just use oem volvo spark plus for volvos. They're very picky. If u take one out you'll know of it is or not. It'll say volvo on the side with three prongs on the top. Otherwise pursue the options i listed above. Usually a misfire will be something simple rather than what happened to me.
 

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Yes, I would definitely check the spark plugs! It is not hard to do and it will give you a piece of mind knowing what they put in there . . . I would also asked myself why have they change the spark plugs in the first place . . . maybe they noticed something already and thought changing the plugs would fix it.
 

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I'm having sort of the same problem:

Volvo S40 T5, Misfire on Cillinder #2.

I recently replaced the spark plugs with Volvo sparkplugs and I have swapped the ignition coils around and the problems remains on Cillinder #2.

If this is a compression problem, what could be causing it?
 

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98 S70 Base, 06 S40 T5 M66 FWD, 08 C70 M66, 11 XC90 V8, 13 C70 P*
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🎵"One of these things is not like the others." Yay, me. P0301 code, oil on the electrodes.
Coolant also low. Everything's pointing to blown head gasket. Compression test next.

'04 XC90 T5 AWD, '06 S40 M66 T5 FWD, '08 C70 M66 T5, '13 C70 T5 ('94 850 Turbo & '05 S60 T5 FWD R.I.P.)
 
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