Missfire Cyl 3 code P0303

twncty · Post by **twncty** » 11 Mar 2011, 08:25

CEL light came on and i noticed that the engine occassionally would seem to have a missfire. I retrieved the CEL code P0303. Would a faulty ignition coil cause this? What else should I look for? Thanks.

Post by **erikv11** » 11 Mar 2011, 09:20

No, bad coil would more likely misfire all the cylinders.

In order of what I would check:
- plug # 3
- cap and rotor
- wire to # 3
- injector # 3

The plug and injector, if they seem fine, you can test by swapping to another cylinder, see if the code moves there.

If it has been a while, get new plugs (Bosch coppers or OEM Volvo) and/or do a tune-up, this generally fixes misfire codes. If you are unlucky there is something worse going on, e.g. a sticky valve.

twncty · Post by **twncty** » 11 Mar 2011, 09:42

Doesnt have a cap & rotor. Individual coils per cyl.

twncty · Post by **twncty** » 11 Mar 2011, 09:43

1999 volvo V70 XC AWD. Sorry for the lack of information.

Wrenchinjoe · Post by **Wrenchinjoe** » 11 Mar 2011, 12:01

P0303 - Would a faulty ignition coil cause this? What else should I look for?

Yes, a bad coil pack for cylinder 3 could cause your misfire, but it could also be a bad or fouled spark plug or the connection/wire in between the coil and plug.

If you are really unlucky, your spark plug could have blown out the head leaving no threads... that is what I am struggling with after getting a P0304.

I hope yours is easy, a coil pack only costs about $50.

nwhitney · Post by **nwhitney** » 11 Mar 2011, 14:23

I just had CEL for a misfore in cylinder 1 and it was the ignition coil, I had already replaced all of my plugs. You could swap the ignition coil from cylinder 3 with another (maybe cylinder 1), clear the CEL and if it comes back on and gives you a misfire in cylinder 1 then you know it's the ignition coil as that is the only condition you've changed. Might be a good idea to change your plugs as well and don't forget to use anti-seize.

Post by **erikv11** » 11 Mar 2011, 17:15

Yes, when there was no car info I assumed it was a 93-98.

+1 on swapping the coil pack, on my Toyota with coil packs I had this, it turned out to be the injector. But that became easy to find out when I swapped the coil packs, cleared codes, misfire code came back on same cylinder.

Jake of Sigourney · Post by **Jake of Sigourney** » 11 Mar 2011, 18:35

Easy fix -- typically coil fails first on middle cylinders. Replace only the bad coil for cylinder #3, and if you have not replaced them recently, also put in some new plugs -(Bosch or equivalent copper plugs are plenty adequate and also cheap) after first blowing out or vacuuming plug recess to avoid debris dropping into cylinder., Autozone carries the coil for about $45.

Post by **rockcandy1013** » 21 Jan 2012, 06:19

New to this site.... I’m an average Joe and can’t afford a mech/shop but I can tell you the advice here is awesome.... I had the same issue.... I have a Volvo s80 t6 2001 almost ran out of gas one evening barely made it to service station.... car smelt like sulpher and jerked as if out of gas ...I filled up the tank and was shocked, it didn’t help car continued to run badly and for two weeks drank more gas than ever, I was getting 10 to 18 mpg where before I was getting 26 to 30 ish mpg......I went to checker and the generic code was p 0303 key word being generic... they told me it was cyn 3 that’s where I started....

I bought plugs and then a fuel filter....don’t rely on Oriely or checker auto parts,.... they told me the bosch plugs were pre gapped..... NOT and then they told me the gap was 40 ..... NOT. There .28 they shouldn’t work there if they don’t know wth their talking about! that said ....I had to re-gap them three times ...... ok so that didn’t help... car still running bad.. No power etc...After reading here and doing research + common sense through deduction.... I bought two coils just in case.... lol.... used and at 25 bucks each from tims Volvo in arvada colorado ( whom I highly recomend ... hes awewsome to talk to and takes the time, cares and to me intrested in your problem ). I bought two because I figured if its two I have them... if not I would had to have wait till Monday....he wasn’t open weekends...... good plan I needed them both..... I replaced one ... better but still sluggish.... I had noticed that when I had to re-gap the new plugs ....cyl 3 and 6 were still ultra clean hmmm I thought still clean means not firing.... so I replaced 6 next and poof working like new and eng light went off and I had another corona !! I do plan on getting a full set of New coils because as we know used is used.... but the point I’m making is this site has been so helpful I personally appreciate it and hope to come here to find more information as needed.... Mark

Post by **Pauloil** » 21 Jan 2012, 16:37

I'd just buy one more for a spare: coils are either good or bad. don't need to go the expense of changing all of them. or maybe you'd like to buy the ipdusa HD ones!