just replaced cat and still misfiring

kcalia · Post by **kcalia** » 19 Apr 2011, 20:23

I have a Volvo 2002 S40 with 92,000 miles on it. i just replaced the CAT and its still misfiring. The spark plugs are good and I am unsure of what else could be the problem. The code for the CAT keeps coming up. Doe anyone have any ideas. I honestly don't know anything about cars.

Post by **JDS60R** » 19 Apr 2011, 20:27

Please tell us what code is coming up. (an example would be P0300)

Post by **FlyingVolvo** » 19 Apr 2011, 20:28

The cat converter usually wouldn't be causing misfires. You ignition coils could be bad (more likely), you could have a problem with your front oxygen sensor, or something else.

kcalia · Post by **kcalia** » 19 Apr 2011, 23:59

i don't know the code right now but i can get it tomorrow from my mechanic but hes at a loss of what its is and hes not familiar with volvo. but from what ive read here and there seems like the s40 is has a lot of issues.

kcalia · Post by **kcalia** » 20 Apr 2011, 21:37

I was told its a cylinder 3 misfire?

Post by **JDS60R** » 20 Apr 2011, 21:40

Sounds like you should swap coil 3 for coil 4 and see if the misfire moves to cylinder 4. This would confirm a bad coil.

kcalia · Post by **kcalia** » 21 Apr 2011, 15:44

he said hes done that coils are fine. new spark plugs. Everything was fine with the car then i got a check engine lite for the cat thats when i felt a chug in the engine when i accelerated fast, other than that it ran perfect except i noticed instead of 300 miles + to a tank i got 200 or less took it in asap switched cat and it hasn't even left the shop because right after the new cat it gave the cyl 3 miss fire. i dk everything that been done because i know absolutely nothing about cars but i know hes tried almost everything he can think of.

Bandit7311 · Post by **Bandit7311** » 21 Apr 2011, 17:57

Ignition coils are a big issue on those models.

If unburned gasoline comes to the cat it will be detected and this unburned fuel can go there because the ignition was not working correctly.

Please look at the ignition coils closely for cracks and / or just replace the ignition coil of cylinder 2+3 (the middle cylinders run over one ignition coil)

Solong
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Post by **JDS60R** » 21 Apr 2011, 19:00

Then check cylinder 3 fuel injector and Mass airflow sensor

kcalia · Post by **kcalia** » 29 Apr 2011, 17:45

im the tech working on the s40 volvo, swoped coils stays on cyl. 3, swaped injectors stays on cyl. 3, checked flywheel pulse wheel windows checked good mass air sensor good,checked timing belt checked good, check compression on all cyl. 175psi, check leakdown on all cyl. check good replaced spark plugs STILL MISFIRES ON CYL. 3 CODE P0303 ONLY UNDER LOAD!!!!! PLEASE HELP ME SO I CAN SALE THIS CAR