2001 s40 misfire cylinder 3 I'm missing the reason

dragonsong · Post by **dragonsong** » 31 Jul 2015, 18:16

I have done a search and looked at the posts, even before I joined. The obd2 gives me the code PO303. Not only that, the radiator blew a hole in itself. Fixed that and changed the oil (no antifreeze, etc. head gasket would appear ok from lack of oil contaminate)

It has spark. Checked it with my spark plug tester.
I did a compression test, C1 150, C2 130, C3 150, C4 150 psi. (three turns each, not sure if that is how many one is supposed to do it, I just tried to make it all the same duration)
While running I pulled the power from the #3 injector. (had problems, i.e misfire as no gas, so I figure, it is getting gas) (Whether it is a good idea, just put some Lucas deep cleaner in the tank)
While running I pulled the plug from the coil. (had problems, misfire from no spark, again, it has spark)
Engine lights comes on, then after awhile goes away, then repeat. OBD2 always reads PO303.
Car chugs or surges under load and low Mph.
I check spark, fuel, and compression. What am I missing? (besides a new car)

I need to fix this or it won't pass smog.

dragonsong · Post by **dragonsong** » 07 Aug 2015, 19:00

OK. I've passed the smog. don't know how or why. anyway, the water pump is leaking, especially after a 30-40 min drive. I get. puddle. when it cools in the puddle is bigger. easy fix?

Post by **Vovo_merz** » 12 Aug 2015, 08:28

not sure about your water pump leak but as for the miss fire, try changing those 2 coils around and see if the missfire goes to a different cylinder I had a similar problem and because in that engine one coil is responsible for 2 plugs some times only one part is working but not the other or not enough spark and if you disconnected the coil fully then you have 2 cylinders not working which makes it even worse.
Good luck

pmondrian · Post by **pmondrian** » 12 Aug 2015, 15:49

I had the same misfire codes for cylinder 3 and rough idling, occasionally. I replaced the coil and wires a month ago and the problem seems fixed.

Good luck!

2001 S40, 180k

S40Colorado · Post by **S40Colorado** » 13 Aug 2015, 16:09

Coils, wires, plugs. * Check boots and wires for cracking and/or arching. plugs for wear