Hi, this is my first post to this forum - I hope somebody can help with some advice.

My wife has just bought an 2003 Mazda 6 1.8S. Although it idles smoothly and pulls cleanly at higher revs, there is a very annoying misfire when accelerating from low or medium revs (1K - 3K). This is, of course, where a lot of normal gentle acceleration is done - around town, pulling out of junctions, etc. It is quite happy to hold any speed - it is just gentle acceleration it doesn't like.

I connected up my PDA to the ODB connector; there are no trouble codes and the MIL is off.

If the problem was at higher revs I would be suspecting the leads - but above 3K the problem is not there (or at least, not noticeable).

Any suggestions?

 

Are there any engine sensors that would cause this if they were failing?

 

I had the same problem, where i would be on the highway and when i went to accelerate it would loose power. I brought it in to my mechanic and the computer said that the cylinder was misfiring. Now they tell me the engine has died because the cataytic converter broke into pieces. I would not keep driving your car because that is what I did and the engine needs to be replaced so they say! the estimate is $7000 because I am over the warranty miles!

 

I have exactly the same issue, please share your fix.

 

I have the same problem, how did you fix it

 

A moderate load misfire, is very often plugs and leads.
Use OE stuff.

I have decided to edit my reply. I realize that Mazda does not make their own parts, but with so many poor options, and incorrect recommendations from big box stores, buying OE does take the guess work out. When you are trying to diagnose a misfire like this, without an onboard scan tool that shows and or records real time info, buying the correct parts is important.
Some cars are sensitive to plug heat ranges, and some plug wires just degrade too quickly, especially when the boots extend deep into the engine head. I have seen on several occasions, with Bosch and Denso, where the only correct spark plug was OE, the aftermarket did not sell them. H9DC0 for example, the dealer always has them, but the big box stores list a resistor plug "replacement", which is incorrect. There is a 1,000 ohm resistor built into the plug wire cap on the OE Bosch and Behr wire sets. You certainly do not want a resistor plug in an application with a resistor cap. Sure you can buy the wrong resistor plugs, but then you need to buy the wrong non-resistor wires.

I did find a set of Belden wires at Napa store that had a lifetime warranty. When the misfire would reoccur, about every 20,000 miles on this certain vehicle, I would take them off in the Napa parking lot, and swap them for a new free set. Napa replacement parts are about the best that I have found, generally speaking. Keep the original empty box in your trunk.


Doing a Google search for "moderate load misfire" may give you more information.

-Does it miss under WOT or only with moderate to heavy load? Is it constant or an intermittent miss? I'd start with swapping plugs with a good ...

-You road-test the vehicle under a light-to-moderate load and you're able to duplicate the ...

-Misfire only when under moderate load points back to the coils.

-I have an 03 with 2.o manual trans.106K It recently started to misfire under moderate to heavy load. and seems to be getting worse.

-Now I have this misfire stumble at low rpm's under a load. If I am going up a ... Stumbling / Missing At Low Rpm With Moderate Load.

 

*****

 

its little of topic, i was looking for thermostat at o'reilly and they suggest me an OE i thouth it should be OEM part from JAPAN and i dint buy it.now i see wats going on