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Discussion Starter #1
A bit of a long story but I'll try and keep it as short as possible.

It all started about six months ago when my check engine light flashed on. I had it checked out and it turned out to be a misfire in cylinder # 4. So the computer was reset and it lasted for a while without the light coming on again.

The second time it came on my mechanic decided to switch around the coils to different cylinders to see if the code would change to a different cylinder. The code remained the same but the engine ran fine.

Fast forward a few months when I drove the car one day and it seemed to be heavily struggling for acceleration(was driving fine for the first ten minutes). Stopped driving it immediately and had it towed to mechanic's shop. By the time it was looked at the next morning, it was back to running perfect again.

Finally about three weeks ago it had the same issue with really sluggish acceleration and a small but noticeable smell of fuel(and/or exhuast).

Took it to my mechanic's once again. He took off the intake manifold and checked the fuel injectors were all getting a signal and there weren't any broken wires. I also had the spark plugs replaced because it seemed like an opportune time. He also checked for an intake leak(which there wasn't one). Since putting it all back together it still has the same acc. issue but doesn't have the misfire issue anymore.

It did however throw out another code(can't remember off-hand) which lead me to replacing one of the rear o2 sensors. Same problem still persists.

I've searched and read a lot of the previous posts on the forum today and from what I've read I'm beginning to wonder if I have the tell-tale pre-cat problem people talk about?

Any thoughts?
 

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Sounds like it could very well be a cat problem especially with the o2 codes. Get a back pressure test ASAP.


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2 things - I don't think you ever fixed the original problem. Just because the ECM is not reporting a misfire, it doesn't mean its not happening. You feel it when it doesn't move the car as it should so that needs addressed. The second part is, this has been going on for months and it may very well have destroyed the pre cat(s) (repeated doses of raw fuel from no ignition).

Often times a partially plugged cat allows an engine to idle fine and maybe accelerate to 3 or 4000 RPM. If it weren't for the risk of fire, pulling the PRE-CAT O2 sensor and doing a very short drive well tell the difference from a plugged cat as the car will rev and make power. If it still has bad plugs, COPs, or fuel issues, those won't change. You will get an error for O2 sensor disconnect. Not that I'm recommending that - just sayin. I suspect you have bad ignition coils. Turn on every accessory that draws energy; seat heaters, AC, blower, High beam, defrost. If doing these actions make it run worse its likely COPs and plugs. Replace them all. Your best time and money spent would be those and visually inspecting the PreCats!

Watch these: 2nd post down and then go talk to your mechanic or buy a 10 dollar tool. http://forum.mazda6club.com/3-0l-v6/258158-final-impacts-running-list-links-help-solve-issues.html
 

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Discussion Starter #4
Just wanted to return here and finish the story in-case other people have similar problems.

Turned out the timing in the motor was off. The one chain jumped a few teeth. Luckily there wasn't any internal damage and the motor was still useable.

Had the chains, guides and a few other things replaced and set properly and the engine is running good again.

Thanks to those who tried to help.
 

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@Ksol what else was done at the time? It would have thrown many codes and RAN like crap all the time with it out of time. Nothing personal but I'd say the mechanic is inncorrect unless there is more to this story.

These do not just jump teeth and be OK - IT DOESN'T work that way!
 
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I had the exact same problem as you have described on my 2.3l mazda 6. Changed the plugs and wire set as they were overdue, and the mechanic said there was a crack in the distributor cap, so replaced that as well. Total cost - 500$. It's been 2 months, and car drives perfectly.
 

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Mine started yesterday. Plugs were changed. I replaced the exhaust plug recently. Part of it was also to exclude the Cat. Will take to Mechanic to give me diagnosis
 
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