Black Spark Plug

[camryguvnor]

Helllpp!!!!

I'm getting a trouble code of P0302 (misfire on cylinder 2) on my 97 Camry LE.

I pulled the spark plug and it has a black shiny(ish) coating on it, including on the electrode. There doesn't appear to be any actual disintegration of the plug, only the black coating. It's not covered in oil, but some of it seemed slightly oily, especially the compression washers at the base of the threads, and there seems to be a light brown discoloring of the porcelein at the base of where the plug boot sits.

Any ideas?

Thanks!

[toyomoho]

If more then one coil pack pack on the engine swap packs and determine if the code number changes.

[camryguvnor]

Thanks.

I forgot to mention that I also previously got a code P0420 (Cat operating below efficiency) although the cat is only a couple of years old and I've only put a couple of thousand miles between the cat swap-out.

[Tony the Tiger]

Originally Posted by camryguvnor

Thanks.

I forgot to mention that I also previously got a code P0420 (Cat operating below efficiency) although the cat is only a couple of years old and I've only put a couple of thousand miles between the cat swap-out.

A misfiring engine will lower EGT's, thus, also making the rear O2 pick up a slow signal that indicates a bad catalytic. Fix the coil pack issue and the cat should be good. Don't wait too long or the rich air/fuel mixture from unburnt fuel will eventually ruin the cat as well.

[camryguvnor]

Just checked the resistance on the coil packs and both seem to be well within the tolerance.

Any other ideas?

[Mike Gerber]

Plug wire(s) or a bad fuel injector to that cylinder can also cause a missfire code.

Mike

[camryguvnor]

Could the plug wire/injector also cause the P0420 cat below efficiency error?

[Mike Gerber]

Originally Posted by camryguvnor

Could the plug wire/injector also cause the P0420 cat below efficiency error?

Possibly. If there was a missfire for any length of time, the unburned fuel in that cylinder (if it was/is an electrical missfire) would make it's way out that cylinder's exhaust valve and through the exhaust system. That means it's going through the catalytic converter. This unburned fuel is pure hydocarbons that can ruin the converter.

Mike

[camryguvnor]

This all happened pretty quickly. I was driving the car for the first time after clearing the P0420. I'd driven 10 miles with no problem and parked it for 15 minutes.

When I started up again I noticed a loss of power for the first time in the car's history. I'd been driving for about 3 miles when the CEL flashed on-off continuously and I hooked up the code scanner while driving (I keep it in my glove box). The loss of power remained constant and every time I reached a traffic light the car was shaking violently on the verge of stalling out. At that point I was almost home and drove the mile to my driveway and there she sits...

Could this all point to the injector/wire or could it be a bad O2 sensor (even though its just a 10K miles old..)?

[hill8570]

Originally Posted by camryguvnor

This all happened pretty quickly. I was driving the car for the first time after clearing the P0420. I'd driven 10 miles with no problem and parked it for 15 minutes.

When I started up again I noticed a loss of power for the first time in the car's history. I'd been driving for about 3 miles when the CEL flashed on-off continuously and I hooked up the code scanner while driving (I keep it in my glove box). The loss of power remained constant and every time I reached a traffic light the car was shaking violently on the verge of stalling out. At that point I was almost home and drove the mile to my driveway and there she sits...

Could this all point to the injector/wire or could it be a bad O2 sensor (even though its just a 10K miles old..)?

That plug's looking like the mixture is somewhat rich, or you're getting a bad burn in the cylinder. Does the plug smell "gassy"? Check some of the other plugs -- if they look OK, it ain't the O2 sensor (as others have stated, if you're getting a bad burn, you'll get a bunch of unburned junk overloading the cat, which will give you a "cat efficency" error from the downstream O2 sensor).

Start with the simple stuff. Swap plugs -- see if the problem follows the plug. Swap a couple of ignition wires -- same logic. Same for ignitors. Pop off the distributor cap -- check inside for anything funky, like a burned contact or carbon tracking. Doesn't seem likely to be a valve issue, but a compression check is pretty easy to do if none of the ignition system checks turn up anything obvious. If all else fails, try swapping injectors, although that's a bit of a pain in the *ss.

[camryguvnor]

Thanks for the reply. I'll check all this in the morning. One thing I will say is that it looks like I have a leak somewhere in the valve cover gasket.

My Camry is a 5S-FE 4 cylinder engine CA-Emissions so it doesn't have the distributor, only 2 coil sets controlled by the computer. I've tried testing the secondary resistance and this looks fine. Could the coil pack still be at fault if the resistance looks good?

I'll try the plugs & wires & give it a compression test if I can get my compression gauge back from whoever borrowed it! If I'm using a non-CA cat & sensors in a CA-emissions car, would this make a lot of difference, other than the tolerances? The cat is definately non CA-emissions as when I bought it the guy told me I only needed a CA one if the car was being driven in CA, which is double the price.

[hill8570]

Originally Posted by camryguvnor

Thanks for the reply. I'll check all this in the morning. One thing I will say is that it looks like I have a leak somewhere in the valve cover gasket.

<chuckle> Par for the course -- the valve cover gaskets on the 5S-FE always leak after a while. Easy enough to fix when you've got the time, but it's not causing this particular problem.

Originally Posted by camryguvnor

My Camry is a 5S-FE 4 cylinder engine CA-Emissions so it doesn't have the distributor, only 2 coil sets controlled by the computer. I've tried testing the secondary resistance and this looks fine. Could the coil pack still be at fault if the resistance looks good?.

My bad -- none of the Gen4 5S-FE rigs have distributors. I spend most of my time dinking with Gen3 rigs, so I tend to overgeneralize. Yes, it's possible for the ignition coil to have it's DC resistance to be OK, and yet be flakey. That's why swapping the ignition coils is a nice diagnostic -- if the misfire DTC moves when you move the coil, you've isolated the problem.

Originally Posted by camryguvnor

I'll try the plugs & wires & give it a compression test if I can get my compression gauge back from whoever borrowed it! If I'm using a non-CA cat & sensors in a CA-emissions car, would this make a lot of difference, other than the tolerances? The cat is definately non CA-emissions as when I bought it the guy told me I only needed a CA one if the car was being driven in CA, which is double the price.

The rear cat should be the same on CA and non-CA. Only the CA had a front cat, so you wouldn't have an option there. I'm pretty sure the CA rigs used a wideband A/F sensor up front instead of the older O2 sensors, while the non-CA rig just used a standard O2 sensor. If that were the case, 'tho, I'd expect that subbing in a regular O2 sensor for the upstream sensor on a CA rig would never work, since the A/F sensors and the O2 sensors tend to have very different behaviors. The downstream sensors on both CA and non-CA were the older O2 sensors (and this sensor would be what triggers the "cat operating below efficiency" DTC). Whatever the case, the misfire DTC you're getting can't be caused by the cat or O2 / A/F sensors.

[hill8570]

Originally Posted by camryguvnor

I'd been driving for about 3 miles when the CEL flashed on-off continuously and I hooked up the code scanner while driving (I keep it in my glove box).

BTW, that MIL flashing means that the misfire and driving conditions are such that the catalyst could overheat (i.e., you're getting a whole crapload of unburned stuff getting fed to the cat, instead of just the occasional misfire).

[camryguvnor]

Thanks again!!

I've had the valve gasket hanging up in my garage for over a year now but never bothered to change it yet

If the MIL was flashing for 10 miles or so, would that be enough to wreck the cat?

Also, as I have the 4-cylinder engine, I have 2 coil packs instead of individual coils. Is it likely/possible that one coil fails as opposed to the whole pack?

[hill8570]

Originally Posted by camryguvnor

I've had the valve gasket hanging up in my garage for over a year now but never bothered to change it yet ?

I know the feeling -- I've got an A/C expansion valve and scrubber for my Sequoia that's been gathering dust since last summer. Since it's still snowing, I'm still not real motivated to change them out .

Originally Posted by camryguvnor

If the MIL was flashing for 10 miles or so, would that be enough to wreck the cat??

Not likely. The flashing is mainly a warning to fix it now, rather than later (I've known people to run around with their MIL on for months before getting it checked).

Originally Posted by camryguvnor

Also, as I have the 4-cylinder engine, I have 2 coil packs instead of individual coils. Is it likely/possible that one coil fails as opposed to the whole pack?

Hmmm. Good point -- usually on the coil packs both plugs fire at the same time. I think it's still possible for one internal connection to go south and the other to be OK. I just hate to rule it out based on "common sense" when it's relatively easy to do the swap, and know for sure.