How can I check the coils on the spark plugs on a 2003 MPV, one is bad and I have no clue as to how to find out which one

 

How do you know one is bad?

 

A mechanic at the dealer did me a favor and did a little trouble shooting, plus coil #3 went bad about 5 months ago and the van is doing the same thing again.

 

What kind of thing is it doing and is the check engine light on? If it is on then have the code # checked. A missfire code will tell you which cylinder is having the problem. The dealer diagnostic computer can pick up missfires and isolate to cylinders even if it is very random and not turning on the CEL. What kind of troubleshooting was performed by the way?

 

Not quite sure what diagnostic was performed, and the check engine light is not coming on. The van hesitates when I accelerate and you can feel the engine missing when in park. I'm going to replace the spark plugs to see if that takes care of it. Any other suggestions?

 

The next best thing you might try is to get yourself a new coil and install in place of the three accessable ones, one at a time and see if the miss and hesitation goes away. That would be cylinders 4, 5, and 6. If it does then problem solved. If not, then faulty coil would have to be at cylinder 1 or 2 since 3 was replaced recently and since you will then be having to remove the entire intake plenum to get at the rear ones and replace spark plugs, you might as well replace them both. The rear ones always tend to fail more often as they get pretty hot back there with very limited air circulation. They are only $59 a piece so would not be a bad idea.
I take it that the van must be out of warranty by mileage over 50k?

 

Yeap! the Van has 52000 miles, so we missed the warranty by 2000 miles. Thanks for the advice. I'll give it a try. Which coil in the back is #3 if I'm facing the van?

 

If you are standing facing the engine compartment with knees at the bumper, #3 is the one on the right or drivers side.
#1 is closest to the drive belts.

 

Thanks!

 

You are very welcome j3412000. The new coil that was installed should be easily identified by the lack of dust on it as well as having different numbers on the top label. Good luck with the work you are getting into. Due to the problems that we have had with the COP in your van it may be possible that Mazda will give a little help with getting it fixed. Always remember, The squeaky wheel gets the grease, and you are not that far out of warranty. I would have rolled back your mileage to under 50k to make sure it was still covered but that is just me