An update on where I'm at and read through this thread, I believe it will help you:
http://www.mazdas247.com/forum/show...ot-trailer-hitching-quot-sensation-in-Drive-6
I read it and decided, that the misfire idea had some merit, so I thought I would start by replacing the spark plugs and checking all ignition coils for secondary resistance. My CX-9 has 70K miles so I was fine with replacing the plugs at this point anyway.
I ordered plugs and went to replace, I checked all the coils and had an open circuit on one coil; the rest checked in at little over 6M ohms for secondary coil resistance. The alldata site says the spec is 5-6 k but I'm positive that's wrong. When I emailed alldata and asked them to double check that spec, the comment was "we don't have another resource to check so we can't give you an answer". Yes, that's really what they told me.
I'm pretty comfortable in assuming that the alldata 5-6 K ohms is an error and it should be 5-6 M ohms. after finding the coil with the open circuit, I decided to order 6 new coils, delivered they were $425; this is a lot but although it's pretty basic to replace the coils and plugs on this car, it does take some time and I really don't want to do it again after having the chamber off twice now. In another thread on this forum, someone had replaced 3 of the 6 and wished they had done all of them so I made the call to replace all six.
On the plugs, I seriously have to question the 100K interval that the dealer told me, at 70K to me these plugs look like they should have been replaced about 40K miles ago. Motor-craft platinums are what came out; I went back together with the Denso iridium plugs. So one of the guys in the "trailer hitching" thread I believe had a cracked plug; to be fair none of mine were cracked, and I looked real close, but both the ground and center electrodes were worn, I say a least .020 inch based what I believe the stock gap looked like. Someone's going to call me out on the .020 so I could post some pictures if that helps anyone.
If the coil was the problem, and it was an undisputed open circuit, the only way I can figure that the cruise control mitigated the symptom is by better control of the throttle body than my foot.
I guess at this point time will tell, there's certainly a risk that the problem will reoccur but with no codes, unfortunately the above is the best I could come up.
In summary; check plugs and coils; what needed to be replaced based on inspection was 6 spark plugs and one coil. I made the election to replace the other 5 coils in an attempt/anticipation that if one coil was bad the other were not far behind. If your going to do this make sure to use a meter and check the coils.
Hope this helps?
