DTC p0421 Prematurely asking for ideas...

[trea's 5]

I'm back again. (dance) Let me start by saying early last month I had DTC issues which were resolved (thanks to the help from you guys!(2thumbs)). Even though it's been a month I'm still not a mechanic. DTC P0421 is my NEW issue. I don't know if the recent history is even related so I will briefly post it. I know this is a little lenghty so I want to thank you in advance for your patience.(blah)

Early October: DTC P0303 / 0660 / 1659
Symptoms - rough in gear up to 1500 rpms, bumping in rpms (did video on YouTube)

Action Taken:
New Plugs (NGK cooper)
New boots/springs
VICS soleniod (just happened to find out it was not working while trouble shooting)
Cleaned EGR (replaced gasket)
New wires (this is what cured the CEL(yippy))

November 17: CEL, I don't remember DTC but had to do with timing.
Symptom - car would not start (you guessed it, the belt was broken)

Action Taken:
New timing belt (plus idler, tensioner, water pump, ac/alt belts)

SIDE NOTE: When disassembling to change timing belt, I noticed the spark plug tip, wire connector side,
had a greenish color on it like - oxidized?(scratch) I cleaned it before reinstalling.
View attachment 189974
After I put it all back together (never done timing belt before) I cranked it and now it has some
pep when you accelerate from a stop. Never been that alive before. (drive2)

Car has been running fine for about 200 miles now. Until...

November 28: CEL / DTC P0421.
Symptoms - None other than the CEL coming on. It still seems to run fine.

SIDE NOTE: On Oct. 2010 (last year) I replaced both the front and rear Catalytic converters.

I have not looked at the car as of yet (son has it at school) but was going to get some ideas/list of things to check. Of course I, like most of you, only like to replace what is broken. Looking forward to your thoughts.

P.S. Did anyone grab that G-oil / rebate I mentioned in the Oct. post? My daughter helped my upload the picture so we had to do the emoticons...

 

[tweety2300]

Could be the precat being bad or the o2 sensor. Does it have a rotten egg smell? Another way you could check is pull the o2 sensor out if its white its bad if its black clean it, it could just be dirty. If it is good then its your precat if you got a cheap one from ebay that's the reason. What you could do is the non fouler trick before replacing the o2 sensor its 5 bucks vs. 60 for an o2 sensor or couple hundred for precat.

Couple off topic questions. Where did you get the vics solnoid? I can't find one anywhere. How bad was it doing the timing belt I need to do mine but I've never done it either.

 

[trea's 5]

No rotten egg/odor at all. I think the cats are of quality.
Rear cat - Walker #WK54484 ($220)
Front cat - Bosal #099-1723 ($170)

Solenoid - OE# KL01-18-741 ($98.14) The solenoid I got from the dealership (couldn't find one elsewhere either). I told him I had a coupon for 10% from another dealership and asked if he would match it. He did better and gave me 20% off.

The timing belt wasn't too bad. It took me longer than most but that's me, no rushing. I read up on it on a few sites and I printed up some instructions as a guideline. Here are two of the links:

Mazda Manual http://protege5.ugly.net/01-10b.PDF
mazdas247 forum http://www.mazdas247.com/forum/show...e-Ttiming-Bbelt-Cchange&highlight=timing+belt

Had to buy timing cover (my top half plastic broke). Couldn't find it at any salvage yards so had to buy a new one. Cheapest I found it was Advance Auto. Received it in two days. Upper and lower cover for $61.25 shipped (after discount code).

I did see about doing the non-fouler before spending a lot of money. I thought that was only if you removed the cat. I saw this link:

http://www.mazdas247.com/forum/show...ure-Cel-Mil-from-removing-cat-with-Non-Fouler

If I am understanding this:
I put spark non-fouler(s) BETWEEN the O2 sensor and where it goes into the cat.
(This causes the sensor to be far enough away so that it will not pick up anything?)
If the CEL goes off, this means that my Cat is definitely bad. (is that right)
If the CEL stays on, something else is the culprit. (is that right)

Appreciate the information and out for non-foulers in the am. TBC (to be continued...)

 

[tweety2300]

My precat is bad I'm using the nonfouler lol. You are right on everything else