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P0430 CAT Below Efficiency, Bank2

The car runs good, no problems. Spark plugs are old, 150,000 miles and 16 years (1997 vehicle).

I decide to change the plugs. No troubles BEFORE I begin.

When I am done, the engine runs poorly, severe -- or at least notable -- misfire. I drive for a day or two -- probably about 50 miles or less -- until the check engine light comes on. I pull codes, a single cylinder misfire. No big deal, I discover the plug wire not seated well on the plug, easy to cure.

Engine instantly runs better -- misfire is gone.

Now I am driving around with the scan tool connected just to be sure that the things I feel in the seat of my pants don't turn into a fresh round of engine codes. I don't feel much, and no misfire reports. Life is good.

Hold your horses, life is not so good.

I have a Pending Code, P0430 CATALYST BELOW EFFICIENCY BANK2. The check engine light has not come on yet, but if the problem is true, then it should come on in a few more drive cycles.

My question is, if I have a misfire will the resulting raw fuel damage the CAT or the post-CAT sensor? I was not aware that a misfire could take a CAT out. The misfire that I had is in Bank2, so there is a correlation between the misfire and the new code.

Of course, there is a strong possibility that the plugs I installed are not the right ones -- just because the parts guy says that the catalog calls for them does not mean they are right. After putting the plugs in, I went to the dealership to get the factory plugs and plug wires -- $230 for plugs and wires from the dealership, ouch! -- but have not installed them because the engine now feels just like it did before I started working on it. (Curing the misfire code fixed the poor operation, entirely, so I'm in no hurry to open the hood again. It was very difficult to reach the plugs, and if the engine runs then I don't want to do the job over again.)

So, my question is if I damaged my CAT or if it is merely a coincidence that I have a P0430 Code in pending status?

Reply to
Jeff Strickland
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raw fuel will certainly damage a catalytic converter, but not necessarily in just a few miles or days. reset the PCM with the scan tool and drive it long distances for a few days and see if a P0430 comes up again. And I might even do that one more time again.

The parameters to set a "cat-efficiency" code are unlikely to occur from a bad sensor, just a bad cat-con. And the cat-con is just as likely worn out from age and not changing the plugs 75,000 miles ago, as from the recent "whoops" with the plug wire.

I am speaking purely of OBDII operational engine mangement theory, not of any case-specific "known issue" on a 1997 BMW/Toyota What-ever-mobile. GW

Reply to
Geoff Welsh

Whilst you were not firing one cylinder lots of unburnt fuel will have got into the cat and 'polluted' it.

Now that all six are firing again, my guess is that a couple of long runs will warm the cat up, provide exhaust with low levels of hydrocarbon and allow catalytic conversion of hydrocarbons in the cat' restoring it to health.

Reply to
R. Mark Clayton

I have reset the P0430, and the code has returned. Several short trips, that's my normal driving profile. I sometimes will drive for 30-ish miles one-way, but generally my trips are shorter.

I would not have thought that I could damage the CAT in the time it took to have the P0306 MISFIRE CYLINDER 6 move from the Pending column to Active.

I'm okay with theory of operation over practical application.

Reply to
Jeff Strickland

You think I can "clean" the CAT? That's a comforting thought. I'm all about saving money, and the wait-and-see method of repair seems logical given the cost of repair.

Reply to
Jeff Strickland

as the other post mentions, you need one good long trip. GW

Reply to
Geoff Welsh

That depends on whether the catalyst has been inhibited (by the condensation of hydrocarbons) or poisoned.

See

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I think the latter unlikely BMW's web site boasts "The system uses a special set of parameters in the engine's warming-up phase in order to help the catalytic converter reach its ideal operating temperature more quickly, lowering emissions..." for double Vanos engines.

A good run will also help in removing oil and / or deposits in the mis-firing cylinder.

Reply to
R. Mark Clayton

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