Mazda Tribute Misfiring on Cylinders 5 & 6

[kalrith]

I have a 2001 Tribute LX V6 AWD with 122,000 miles on it. I bought it with 80,000 miles on it 3 years ago. 2-3 months ago was the first time it misfired. The throttle was very shaky, it had a hard time accelerating, and the check engine light started flashing. I immediately had the light checked at AutoZone and was given the above codes that say, "The PCM has determined that a misfire has occurred in cylinder #5...#6." The print-out from AutoZone says the possible causes are ignition system fault, vacuum leak, injector fault, and high or low fuel pressure. What's strange to me is that it runs perfectly fine 95% of the time and then misfires badly about twice a month.

I replaced the DPFE sensor (a known problem on the Tribute and the source of a lot of problems) about a month ago hoping that was the cause, but it's happend twice since then. I'm wondering if I should replace the EGR valve as well. I checked the sparkplugs and ignition coils in the front three cylinders, and they all look good. I haven't tackled getting to the back three cylinders yet because I'll have to remove the intake manifold and possibly more to get to them.

I have two big questions that would greatly help my troubleshooting of the problem. Could someone please tell me which cylinders are which, so I can locate cylinders 5 & 6? Also, what would I need to do to swap the ignition coil from one cylinder to another to see if that is the source of the problem?

Thank you very much!

 

[Vetterin]

Firing order 1-4-2-5-3-6

Location:

1 - 2 - 3

4 - 5 - 6
Frt of Eng

 

[iamwiz82]

By chance is the 5% of the time when it's damp or rainy out?

First thing you should do is swap out the spark plugs, wires, then the coil packs.

 

[kalrith]

Thanks for the help, guys! I know the problem has occurred when it's damp out, but I'm not sure if it's limited to that. It happened this morning, and it probably hasn't rained since 10:00 last night, although it did snow a little since then.

I guess I should get some new spark plugs and wires and see if that fixes it. Does anyone have a recommendation of what spark plugs to get or from where to order them? I usually just buy my parts at AutoZone, but since this isn't an emergency I'd order them online if they're cheaper.

Since cylinders 5 & 6 are both in the front of the engine (and therefore much easier to get to), would there be anything wrong with just changing the spark plugs and wires up front?

 

[kalrith]

Well, I've done some troubleshooting, and it seems that the ignition coils are the culprits. I replaced the spark plugs in cylinders 4, 5, & 6; switched the ignition coils between cylinders 4 and 6; and reset the check-engine light. The problem's still there, so I had the check-engine light checked at AutoZone today. Now cylinder 4 is misfiring, which is either a really big coincidence or shows that the ignition coil is bad. I ordered two ignition coils for $131 shipped, so hopefully that fixes the entire problem.

Edit: BTW the problem is much more frequent now, probably occurring about 70% of the time.

 

[alpineranger]

Often when those coils go bad it isn't obvious upon visual inspection. A repair manual will give you the proper diagnostic procedure for your car and it usually involves just a multimeter.

 

[Eli]

Originally posted by: kalrith
Well, I've done some troubleshooting, and it seems that the ignition coils are the culprits. I replaced the spark plugs in cylinders 4, 5, & 6; switched the ignition coils between cylinders 4 and 6; and reset the check-engine light. The problem's still there, so I had the check-engine light checked at AutoZone today. Now cylinder 4 is misfiring, which is either a really big coincidence or shows that the ignition coil is bad. I ordered two ignition coils for $131 shipped, so hopefully that fixes the entire problem.

Edit: BTW the problem is much more frequent now, probably occurring about 70% of the time.

 

[iamwiz82]

Originally posted by: alpineranger
Often when those coils go bad it isn't obvious upon visual inspection. A repair manual will give you the proper diagnostic procedure for your car and it usually involves just a multimeter.

Sometimes you can see the coils arcing. All you need to do is run the engine while it's dark and mist the coil packs with water lightly. Look for the light show. Obviously it's not 100% certain you will see something, but you might.

 

[exdeath]

Very common on overhead cam engines due to the deep spark plug recess at the top of the engine and the rubber boots that can trap moisture.

Check the seal on the coil pack cover if you have one, and make sure the grommet where the coil signal wires come into the top of the valve cover are seated properly. The coil packs probably aren't bad, I bet they are just wet. Remove them from their rubber insulation boot and air them out, and hose out the spark plug recesses with compressed air.

 

[Adam Ward]

Hey guys...I have a Mazda Tribute and a misfire eventually killed a cat. the problem isn't always the coils, many times its a green and white wire that comes off the pcm that is known to break inside the wire coating. So check the wires that go from the pcm to the ignition coils for continuity, it can be tricky, sometimes you'll get continuity but if you shake the wires around the misfire will immediately go away. That will give you your answer. I can't tell you how many ppl replace coils when it's actually a loose or broken wire off the pcm....good luck!