Hi everyone. New member but have been lurking for a while.

My daughter has a Mazda 6 2.3l 4 sp AT. A few days ago she stated that it suddenly became very "jumpy" when taking off. She and her mother both thought it was the transmission slipping so I had her pick up a filter kit and fluid and bring the car to me to change. I changed the fluid and filter ( not a full purge). After servicing the tranny I drove the car and found that it seemed the transmission was fine but it was an engine problem. It really struggles on acceleration and CEL flashes but seems to level out when cruise speed is reached.

Went to Autozone and got the following codes:

P0301: Cylinder 1 misfire detected

P0420: Catalyst efficiency monitor malfunction-bank1.

P0456: EVAP control system leak detected- very small leak

P0128: Coolant thermostat condition- low operating temperature.

I know misfiring and a poorly running engine can clog a CAT over time, but can a clogged CAT cause a misfire? Or maybe the two are unrelated.

I did change the plugs (Autolite Platinum) with no help. I guess my next step would be to change plug wires and the faulty CAT.
I would appreciate any advice or troubleshooting tips anyone can give. I hate to just keep throwing parts and $ at it.

 

Merle:
I too hate to throw parts at a problem. We are on the same page.

I change plugs and wires together. My suggestion is: replace the wires too.

The evap code could be caused by a leak at the gas cap. Check the mating surfaces and the O-ring at the gas cap. Make sure it's tight. Check the evap hoses under the hood for good condition.

You may need a new thermostat. Possibly your thermostat doesn't close anymore. While you are at it you may flush the whole cooling system.

A clogged cat will affect the flow and can cause misfires. Now don't jump to replacing the cat before you do a few diagnostic / cheap repair things.
When the tank is half full add 1 gal of Lacquer Thinner (NOT PAINT THINNER!!!) to the fuel and drive for about 100 miles, then fill up again. The lacquer thinner will clean everything it gets in contact with including the cat and O2 sensors.

Disconnect and reconnect the wire harnesses of the O2 sensors. Corrosion there may cause a false signal.

If that doesn't help you can take out the cat inspect it and wash it with laundry detergent.



Also you can let a shop measure back pressure in the exhaust to determine if the cat is blocked , or you can use a temperature probe to read the temp before and after the cat. It should be hotter after the cat as the cat burns off unburned fuel.

That way you know you needed a new cat, rather than guess.

Good luck!

 

Thanks for your quick reply and advice. I have a few questions.
How many CATS are on a 2.3l engine?
How many O2 sensors and locations?
Can you tell from the TC's which O2 sensor could be giving the issue?

Thanks again for all of your help!

 

i would first fix the coolant temp sensor. then the lacquer thinner trick. then troubleshoot the misfire. and check/replace the spark plugs. if the temp sensor is sending bad info to the computer the car could act weird. for example, if the computer thinks the temperature is low, it will think the car is cold and should be run a little rich, even run in open loop, ignoring the readings of some other sensors, like the o2 sensors.

 

Thanks, Juanky. Where is that temp sensor located?

 

Merle:

I suggest you get the haynes manual for this vehicle. It will show you the location of most parts and in addition it gives you torque values and test procedures. These are $20 well spent.

 

its better to google for that info or get the manual.

 

found in 5 seconds:

 

Thanks for all the info, guys. I work a lot and live about 30 minutes from my daughter so her mom ended up putting the car in the shop. Hope she doesn't get reamed too bad. I'll update when I hear the final diagnosis and repair.