Failing Coil Pack Caused P0430/P0420

[Picasso]

I've been trying to diagnose sudden poor engine performance, that includes engine vibration, since getting a dealership oil change back in May of last year (2006). The long story about that is in this thread.

After previously discovering and correcting a clogged fuel filter and a leaky PCV valve grommet, I recently discovered that the coil pack over cylinder #8 had partially failed, a state it has probably been in since the dealership oil change from 18 months ago. This was unexpected as I have heard virtually nothing of partially failed coil packs and their symptoms.

I had just completed the 90K maintenance items, except for the timing belt, and the engine still had the same symptoms, namely vibration at idle and highway speeds and a strange pulsing exhaust. The readings on my recently purchased scan tool showed no indications of any problem except for a P0430 (low catalyst efficiency, bank 2) which had started a few days before doing the 90k maintenance. I took a close look at the O2 sensors with the scan tool and didn't find any sign that they were faulty. There were no detected misfires and the plugs that I had just removed all looked the same, which offered no clues.

The only thing that I hadn't touched were the coil packs, so I swapped coils 6, and 8 with coils 5, and 7. Low and behold I suddenly got a pending P0420 (low catalyst efficiency, bank 1) after one short highway drive. The vibration at idle was still there but was now at a different RPM. Moved coil 8 back to its original cylinder and no more P0420.

Replacement of coil 8 resulted in significant reduction of the engine vibration at idle as well as at highway speeds. The pulsing exhaust at idle is now gone. The seat of the pants dyno tells me that torque has improved too.

I'm not certain why a partially failed coil would cause a P0420/P0430 but all of my cylinders looked like a 10 year old campground charcoal grill when I shined a light through the spark plug holes. The plugs that I pulled are much darker than the ones pulled 30k miles ago. Both sets are NGK BKR6EYA - V groove copper cores. Could it be the substantial carbon build up with the bad coil that caused the trouble code?

I did a Techron treatment in my last tank of gas and am doing a BG44K in my current one in an attempt to clean up the carbon. Hopefully this will take me the rest of the way in eliminating the remaining symptoms.

Just thought I would offer this insight to the board. Would also like to hear anyone else's thoughts on what is going on regarding the partially failed coil pack and the P0420/P0430. Anyone else experience something similar?


Paul

PS: The new Denso coil pack has a different part number from the ones that were stock on my 2000.
Original Part #: 90919-02230
New Part #: 90080-19027

[HOGWILD]

I checked prices for coil packs the other day at my local dealer and the wanted like 93.00 per coil and do not put off that belt too much longer you never know when it will let loose and if it does i hope you have a non interferance engine

[Cian]

Picasso -

Thanks for reporting back.

It's good to hear you've resolved your problem, although admittedly, being a newbie I'm not certain I would have had the same success.

[Picasso]

Just an update on my ignition coil problem.

I have now replaced ALL 8 coils. Yes, they were all bad. Not completely failed, just not anywhere near 100%.

Replacement of the first three coils resulted in very noticeable improvement in engine smoothness and performance while at idle and while driving. After the 4th coil was replaced, my engine quieted down significantly which was very surprising. This noise was similar to what I would have expected with a failing bearing for one of the accessories that is driven by the serpentine belt. This was most notable while driving slowly. Completely gone now.

I next replaced the remaining 4 coils one at a time to see what kind of improvement would result and to confirm whether or not the original coils were faulty. Improvements were achieved all the way through the 8th coil. Of course.

My obvious concern is that since I don't know what caused all 8 coils to go bad that I will have to repeat this expense in the near future. The most likely cause is, I hope, the fact that when I pulled my plugs to check them after my engine symptoms first appeared, I found that they were gapped incorrectly with the gap being to wide. This could have caused the coils to be overworked which then led to their failing. Did I have a brain fart and gap them wrong when I did the 60K maintenance? Possible.

Another possibility is that there is a loose ground wire in the wiring harness. I checked the main grounds that the coils are attached to and all connections looked good. I'm going to go through the electrical schematics to see if there are any additional connections that I can check.

My truck is still not 100% as other problems remain which I discuss in the other thread.


Paul

[ddvk]

You must count it as luck that your coil packs held up for 8 yrs, many don't. Like my 2000 Maxima had coil problems from 45K miles, then I replaced all of them with 2001 coils at 65K and now it has 140K on the odometer and running strong.

Many engg problems are there in introduced vehicles, that is why there is a saying "Buy the vehicle from last yr of the generation". Like a 99 Maxima is worth more than a 2000 Maxima, there is a reason for that, least bugs.

Now coils get destroyed for a number of reasons. One of them is plugs.