Re: 1999 Miata - Check Engine - Help

Pat Dreiding wrote:
> I need a few words of wisdom about my '99.   It has 65K miles on it.  
> About a week ago I did something that I believe was very stupid.   I 
> cleaned my engine by hosing it down.  The car ran ok for a little while,

> but then stopped.  The engine light was on. Yes - you guessed it.  Water

> in the plug wells.  Ugh!  I spend the time to remove the water and dry 
> the wires & plug wells.  The car was running fine for another few days 
> afterwards and then the check engine light returned.  The autozone tech 
> told me the trouble shooting error code is P0420., which is:  "Catalyst 
> efficiency low-bank .  - the oxygen sensors monitor the catalytic 
> converters ability to store oxygen.
> Possible causes are:
> 1. Catalytic converter defective (Failure possibly due to #2, 3, or 4);
> 2. Engine msfire or running condition;
> 3. Large vacuum leak;
> 4.  Engine oil leakage into exhaust-value guide seals, piston rings
> 
> Any suggestions on approach to uderstanding and fixing the problem?
> 
> I've been considering replacing the plugs & wires.  Is this the correct 
> first step?
> 
> Thanks,
> - Pat

That is what I would do. The plug wires are probably due for replacement 
even if they are not the problem. It is likely to take care of the 
problem and is fairly inexpensive and easy to do.

How does the car drive? Bad plug wires will cause hesitation on take-off.
A bad catalytic converter will probably cause you to suffer a loss of 
power that is constant and it may get worse with increased exhaust flow.

If it is problems #3 or #4, then it is probably not related to the 
engine wash, unless you possibly sprayed a vacuum hose loose.

Good luck!

The other Pat