Engine Misfire or Transmission Issue?

[Khagghen]

I am hoping to get some guidance on a problem that I am having with my 2007 CX-9.

The problem occurs when I am cruising just below 60 mph and around 1500 rpm in 6th gear. When I apply the gas lightly to accelerate, the vehicle seems to "stutter" right around that 60 mph mark, the car seems to jerk/hesitate for a few moments. This will happen on a couple of occasions before the issue simply goes away. The only times it seems to occur is under the scenario described above although I have felt a slight jar when the car shifts into 4th, but nothing like the hesitation right around that 60 mph mark.

The transmission is smooth almost always under 60 mph with that rare jerk into 4th gear I mentioned and once I am above 60 mph the problem does not recur. When this issue happens, it almost feels like the car will stall as it lacks the normal power during the episodes. There is no noise associated with it. There is no check engine light and when I took it into the shop, the diagnostic did not pick up an fault codes. I was thinking is was a transmission issue, but when I took a test drive with the mechanic, he felt it might be more of an engine misfire.

I have read a number of the postings in the forum and while some seem close, I haven't come across anything I would say is identical. I am hoping that the community here can point me in the right direction.

Thanks.

 

[jk240sx]

Strange there is no code. could be coil pack, plug, wires or a fuel injector. All of these can cause a misfire.

 

[ceric]

What is the mileage of your CX9?
If it reaches 100k, it might be a good idea to replace the plugs.
If not, try 89octane for a couple tanks and see if the problem go away.
Did you ever replace the transmission fluid?
It could be one of many reasons, but start with cheaper ones.

 

[bumparker]

I have not done any engine work on our CX-9 but the engine is basically a Ford engine and I have had some experience with Fords. My comments are generic and not specific to the CX-9. The intermittant miss you describe without throwing a CEL sounds very similar to a miss that is common in newer Ford V8 engines. Most new engines have a COP (coil on plug) on each spark plug. On modern engines the spark plugs are buried pretty deep in the engine and there is access to the spark plugs through a tube built into the valve cover design. The COP has a spring several inches long that attaches from the main body of the COP to the end of the spark plug, the spring carries the electrical pulse to the plug. Since the spring is sitting inside an aluminum tube which is part of the engine (grounded) to prevent the electircal pulse from grounding to the engine instead of firing the spark plug the spring is encased in a flexible rubber insulator. These rubber insulators get a lot of abuse based upon where they live and over time they tend to crack, when they crack you start to get intermittant miss fires such as what you have described (mine started to fail around 70k). The good news is the insulators are pretty cheap and there are only 6 of them, the bad news is changing the insulators is the same amount of work as changing the plugs. Also, without a CEL code you won't know which insulator is causing the problem although if you change one you should change them all. If my comments don't apply to the CX-9 I'm sure the moderator will chime in and let you know.

 

[Khagghen]

The car has 116K miles. I have read more posts over the last day and I see some similarities with people who have been have had a similar problem resolved by either replacing the spark plugs and coils or replacing the throttle body. I have a 3rd party warranty which does not seem to cover either of these repairs so that will not be good.

I am not the original owner so I am not sure whether the transmission fluid has been changed prior to me taking ownership of the car.

Thank you all for your comments, I will start by looking at the spark plug replacement and update when I have taken the car in for repairs.

 

[kornholio]

I had a similar problem with mine. It happened when i would accelerate on an incline. You get a flashing check engine light and once it stops the check engine light goes off. If you have an autozone nearby you can borrow the code scanner and check for a code. That is what i did even though the light was off. The code is usually stored as a pending code.

 

[Winstond]

116k miles? Sounds like time for some new spark plugs and based on what the original poster said might as well do the insulators too.

If ur car is acting up, first plan of action would be to perform missed maintenence.

 

[bumparker]

I think the missfire is the most likely culprit. I would change the plugs and insulators first. I bet that solves the problem. Having said that, the plug change on the CX-9 is a little more involved because you need to remove the intake to access the rear plugs. Search the forum for instructions on how to perform, there are some utube videos on how to change plugs on transverse 3.5L Ford engines in CUVs (similar) that can assist if you are planning to do the work yourself.

 

[boltsfan74]

I had the exact same problem. I took it in to a mechanic to get the transmission checked out but they found no problems. A few weeks later it started doing it really bad at any speed and it turned out that the plugs were shot and one of the coils actually melted. I replaced all of the plugs and the coil but now it's back to sputtering at different intervals.