'02 S40 1.9L Turbo Automatic. 198k

I've been having what seems like a lot of backfiring lately. It is most apparent when accelerating or idling. When idling it sometimes feels like the car is about to die. I had the parts place pull the codes today.

P0420 Cat System Efficiency Bank 1
P0015 Cam Shaft Position over retarded Bank 1
P0456 Evap System Leak (slow leak)
P0131 Oxygen Sensor Circuit Low Voltage Bank 1 Sensor 1
P0302 Cylinder 2 Misfire

I have replaced all wires, both coils, and spark plugs in the last 6 months - but the problem has remained. I'm thinking next is the O2 sensors (I'll replace both) and then the cat converter.

Any other thoughts? Am I on the right track? It looks like the 02 sensors won't be too hard - the Cat may need a torch... anyone know for sure?

I'd let this thing just go to the junk yard - but I just can't right now.

Tinman.

 

Before you start replacing the O2 sensors and the cat, check for vacuum leaks including the line to the Evap system. I'd be more concerned about the cam shaft position error. That can be caused by a bad cam shaft position sensor, a sticky VVT or the timing belt being one notch off (cam sensor is most common but there's enough posts on sticky VVTs).

To replace the cat, there are three bolts between the flex pipe and the turbo - and then the clamp to the rear muffler. They are not through bolts so take care removing or you'll be drilling out a stud (ahem, been there...). Plenty of PB Blaster and patience required but doable. A shop can do this for about 1 hour labor if you don't want to take on yourself.

If you are doing the cat, you might as well do the O2 sensor so consider that one big job. You can save some $$ by using the generic Bosch 4 wires (they splice into the old cable via shrink tubing).

My two cents would be to resolve the 0015 and 0456 codes first then worry about the O2 and cat - if you find a vacuum leak or a bad position sensor you may see those codes go away on their own. If the position sensor is good, you may want to try a Sea Foam treatment to see if that sets the VVT right (again plenty of posts on this approach).

 

So a few things have dawned on me today. I have noticed a significant decrease in backfires. I think it is because I was messing with one of the evap hoses yesterday just to see if they played a part as soon as I pushed the hose in, the backfiring reduced significantly... it's not gone, but it is reduced a lot. I remembered today that I recently replaced the vacuum pump and the hose going to the throttle body and break booster the other day. I bet my leak is there someplace! I replaced it with a hose from the yard... so I'm guessing I need another hose from the yard and I should be good. Maybe I'll get a new one this time so I know it's good.

I did have my transmission flushed and oil changed this weekend - not sure if they had to mess with that hose or not to get to the tranny to change the oil or not, but maybe they did. If they did then that would explain the increased missfire until I pushed the hose in which created a bit better seal.

I took a look at the timing belt. No oil on the belt, and I just replaced it in December along with the cam shaft seal and a few other things. My wife did tell me that the check engine light flashed the other day when accelerating and the backfire happening a lot. I noticed this once before too. I bet the misfire / backfire is causing the cam shaft to retard. I bet if I fix the backfire my problems with the cam shaft will go away.

I'll try to post a picture of the vacuum hose that I think is the culprit...

 

Click photo to make it larger

http://www.partsgeek.com/catalog/200...cuum_hose.html
Now I know why I went to the yard to get the hose - $122 for a hose - yikes!

I'd love to get some confimation that this hose might be my culprit before springing the dough.

 

same part is $92 at tascaparts.com...