I have a 2002 Mazda Tribute V6 with 151K. My check engine light has come off and on for quite a while now, mostly it would come on when it rained and then go off when the weather cleared. When it was on, the engine would sputter or misfire. I first had Auto Zone hook it up and they said it needed its plugs and wires changed. No problem. I took it in to a repair place and was informed that I don’t have plugs and wires, but something with coils and that since it was impossible to determine which coil was bad, all would have to be replaced at a cost of $1500. I then took it to another repair place and they said the same thing. Now I have seen some discussions regarding this same thing and apparently some people have been able to identify a specific coil. At this point my check engine light is now on all the time and I’m really worried about doing terrible damage but I honestly can’t afford $1500! I would appreciate any suggestions!
You need a mechanic with better tools. The right computer interface can plug in and read the system while it’s running, and tell which cylinder(s) is(are) misfiring, and replace just what’s failing, not everything.
I agree with chaissos. You’re not talking to the right mechanic.
Please elaborate about where you took your Tribute. Are the places you visited part of a national chain? Did you consult a Mazda dealer? Have you talked to an independent mechanic? We need to know these things.
If the light is on for a misfire, the computer should tell the mechanic which cylinder is misfiring. It’s not rocket science.
Whoever said you don’t have plugs and wires is partially incorrect. Your Tribute has spark plugs, and it has wires, but it probably doesn’t have a traditional ignition coil.
I believer your Tribute has a “coil-on-plug” ignition system.
My suggestion? Find a good independent mechanic. Stay away from the national chain shops, or the tire stores, oil change franchises, etc. You need a mechanic, and when you find one you will be amazed at how simple it is to get your vehicle working properly again.
You will, of course, have to write a check, but if you find a good mechanic it will be worth every penny.
You should not rely on AutoZone for a diagnosis nor should you assume part of their job is to provide a diagnosis. Their job is to scan the car and provide a code, or codes, to you. Nothing more.
I’m in agreement that you likely do not need all of the coils changed en masse.
Questions though.
Does this car have the original spark plugs in it? If so, ouch. That can be a coil killer.
What code or codes are shown? Without knowing the codes we can’t even begin to make an educated guess.
Oh wow. Thank you for all the feedback. I will go look and find the information I received regarding the codes. I cannot remember the first place I took it to, but I don’t think it was a national chain. The second one was a small independent mechanic who was performing my vehicle emission inspection. I have not taken it to the dealership yet. Thank you for the input, and I will update later with more information.
I found the print out from the diagnostic machine. It says: "Cylinder 4 misfire condition detected. Probable causes: lean air/fuel ratio; weak ignition system; engine mechanical condition; vacuum leak affecting one cylinder."
As far as I can see on the slip, there are no codes referenced.
I did find another document that looks like it may have been from one of the mechanics noting an ignition coil, spark plugs, ignition cables and ignition timing/idle speed.
Does this help?
Ignition timing or idle speed would not be the cause of a Cylinder 4 misfire.
What should be done is to remove the spark plugs and run a compression test on all cylinders as a first step to make sure there are no engine mechanical faults. The readings should all be close to each other and considering the mileage on the vehicle, and assuming the engine is in good condition, you should see around 170 PSI on each cylinder.
The spark plugs should be replaced if pressures are good and the spark plug contact surface inside the coil boots should be inspected for corrosion, etc.
You should avoid the shop that recommended replacing all of the coils. An expensive shotgun wild guess at a problem without even verifying there are no mechanical faults first is not a smart move.
So from reading the above comments I have spark plugs AND coils. Ok. I’m printing out this discussion and taking it with me so I have talking points and don’t sound like a crazy person to the mechanic.
Should I take it to the dealer or just get a recommendation for a good independent mechanic?
Yes, you have both spark plugs and coils. The spark plug is the item that creates the elctrical arc (spark) that ignites the fuel in the cylinder, creating combustion and power. The coil is a device that generates enough voltage to jump the spark plug electrodes creating the spark. 12VDC won’t just that big of a gap in that environment. The coil does this by creating a magnetic field (via a coiled wire) around its iron core and at the prper time allowing it to collapse into the core, creating a voltage “spike” of many thousands of volts.
In BC (Before Computers) there was one coil. The high voltage spike was distrbuted to each sparkplug at the appropriate time by the distributor. The “appropriate time” was determined my mechanical parts in the distributor, the rotor and contacts on the distributtor cap. On modern engines, each individual sparkplug has its own private coil. The timing can be controlled by the comuter, so there’s no longer a need for the distributor’s mechanical parts. Placing a coil right on each plug also eliminates the sparkplug wires, which were prone to the insulation breaking down as they aged.
Um, I have a question: are these the original sparkplugs? With 151,000 miles on them? If so, I think I know why your #4 cylinder is misfiring. I’ll bet my morning muffins that the electrodes are eroded. That leaves too large a gap for a reliable spark. I’ve attached a link with pictures of sparkplug electrodes so you can see what they look like.
I hope I’m right.
Thank you for the explanation and the visual aid! As far as I know yes, these are the original spark plugs. When I bought the car it was 2 years old so I doubt they would have been replaced before I purchased it and as far as I can remember, I don’t believe I’ve ever had them replaced. From what everyone is saying, the spark plugs are definitely what I need to try first (and hopefully last!)
Thank you!!
It’s time for the maintenance schedule lecture In addition to resolving this issue, you need to examine the maintenance schedule for this vehicle and get it up to date. That would include fluid changes (including ATF), filter changes (more than just oil changes). Your spark plugs are most likely 90K to 31K overdue and that is the most likely basis for your problem. Bringing your maintenance up to date will extend the life of your car.
At this point you had better hope those plugs come out without damaging the threads in the spark plug holes or plug replacement is going to get expensive due to thread repairs.
I would add that leaving plugs in for periods like this can also damage O2 sensors, catalytic converters, etc, etc.
If you have plugs and/or a coil replaced and IF a problem develops in the future with poor running, CEL illuminated, etc. do not automatically blame this on the shop. It will likely be a result of the previously neglected maintenance.
I’ve found that for stuck plugs, if you can move them about 1/2 turn, spray some WD-40 (or silicone spray or any other spray lubricant) around the base, and let it soak for about 5 minutes. Then, gently tighten/loosen, back and forth, until the spray works its way in. Spray more if you need to, and keep at it gently until they back out.
I’ll get flamed for saying silicone, but I use it regularly, and it works fine for me. You just can’t start the vehicle for about an hour afterwards, until the spray all dissipates (it will set off the CEL). Longer if inside, shorter if outside (air movement). You don’t want to spray whatever you choose to use all over the engine, just some at your work point.
Chase
The fact the the car runs fine until the weather is damp is a huge clue. It indicates the most likely cause is somewhere in the high voltage system. Any dampness at all will short out the high voltage if any insulator is cracked. Sometimes you can’t see the crack it is so tiny, but it still can short it out if water gets inside. The coils, the wires, and connections between the coils and the spark plugs, are the primary suspects.
I had a similar problem on a 1978 VW Rabbit, where it would run fine as long as the weather was dry, but the first rainstorm & it would sputter like crazy. If I ran over even a puddle of water that splashed, the car would stop running! I looked at that coil about a dozen times and couldn’t see anything wrong. I finally go fed up and removed it, and then I noticed a tiny crack on the underside. A new coil fixed the problem straight-away.
When your mechanic changes your spark plugs out, they need to check for carbon tracking on the boot of the coil that is misfiring. That can definitely cause rough running in damp weather and can eventually lead to rough running at all times, if it gets so bad it becomes the path of least resistance. If there is carbon tracking, the boot will need to be replaced, if it can be obtained separate of a new coil.
Replace all the spark plugs. When doing the plugs replace all the rubber boots that cover the spark plug and connect it to the coil. These rubber boots deteriorate and often the boot is bad and the coil(s) are fine. After doing these things see if all you problems are resolved. If not, then one coil is likely bad any a good mechanic can identify which one of the six is bad, either by a code, or replacing each coil one at a time with a known good on until the bad coil is identified.
I give it an 80% chance that new plugs and boots will do it. The boots should be available from a NAPA store as a separate kit so you don’t have to buy a new coil(s) to get new boots.
Wow, 150K on spark plugs? I changed mine at 70K. I don’t even want to ask about oil changes. Homework, sit down and read owners manual maintenance schedule. You might want to go to a super duper mechanic or dealer for the plug changes since it might be a big problem getting them out.
Oh my goodness. Well, clearly the general consensus is that I am apparently a moron regarding general maintenance. I will accept that and do better from here on out. Per the blue book, the current trade in value is anywhere from $2400-3400. At what point in the repair process (if it is a bigger deal than spark plugs) is a good time to re-evaluate? $1500??
No, the general consensus is simply that you’re not as knowledgable in cars as some are so you reached out for help. That’s smart.
It’s unlikely to come to that decision. From every indication so far the problem, whether it turns out to be a spark plug or a spark plug plus a coil, it’s relatively minor and not internal to the engine. It’s apparently isolated to one cylinder, making diagnosis easy and pretty much eliminating the expensive stuff like the crank position sensor.
This is simply a normal minor glitch for a vehicle with 151,000 miles on which the maintenance has not been kept up…as suggested by the original spark plugs. The way to avoid these glitches (and more serious ones) is to read the recommended maintenance schedule that came with your owner’s manual, get the vehicle up to date, and keep it up to date. Post here if you have any questions on any of it.
OP, just replace the plugs and all 6 boots first. NAPA should sell all 6 boots as a “kit” for around $20. Each coil could be $80 and that is what is driving up the costs, 6 X $80 is $480. Likely only one coil (if any is bad), so do the plugs and boots first and then isolate the bad coil if there is one.