Can't figure this one out!

[jdwk]

The cat is filled with a bunch of plates coated in platinum. It is not uncommon for those plates to break off over time and rattle inside the cat. And yes our stock mid pipe has two catalytic converters.

However, unless it it really plugged up, the cat doesn't have much affect on how the car runs. The secondary O2 is just there to make sure the cat is functional, it doesn't affect tuning at all.

Don't take the manifold off and replace the gasket until you check your trims. That will give you a much better idea of what is going on. I would replace that gasket as a last resort. There are a lot of places for vacuum leaks to occur, and rubber hoses are more likely to crack over time than two pieces of metal with a paper gasket sandwiched in between them to spontaneously separate on their own.

 

[01CrznMp3]

Exactly as JD says....the cat when it gets really bad you will lose a lot of power. When you go to nail the gas it will bog and you will hear a bunch of hissing noise. Thats a whole different situation and has nothing to do with your original problem though. The intake is just 6 or 8 bolt/nuts and you dont have to take it completeley off. Just slide it back far enough to slide gasket off and new one on unless the gasket doesnt come off in 1 piece and needs scraped off. But as JD said check for other leaks prior, hoses are a simple fix and go bad regularly.

 

[mazdarichie]

Well I tried the carb cleaner. Nothing. Let it fully warm up and start running like the usual crap and sprayed again all over the vacuum lines and around the manifold. No change at all. I feel like I will never figure this out! I wish it was something as easy as a vacuum line.

 

[jdwk]

What is the word on the trims?

 

[mazdarichie]

I don't even know what the trims are and how I read them. I have a basic scan tool that will tell me what codes I have and that is pretty much it.

 

[jdwk]

I recommend getting something like this.

https://www.amazon.com (commissions earned)

Then you can get the Torque app for your smartphone to see everything our PCM is capable of displaying over OBDII. If you don't have a smartphone, there is a bunch of software out there to run on a windows machine.

You can buy the handheld datalogging scanners like Cenntech, but they are a lot more expensive and not nearly as useful as a bluetooth device.

 

[mazdarichie]

Well I have this one:https://www.amazon.com (commissions earned)

 

[Spiced MSP]

that rattle could be the heat shield on the j pipe. Just an idea

 

[M2P503]

No more thoughts on this? I guess I will just have to keep trying to figure this out on my own.

Hey man im sorry your car is running like crap and if you have honestly tried all of the tips above from everyone on this thread and it's still running like crap then just sell the car!

 

[mebarsh]

if you thinks its the cats possibly disconnect the exhaust at the j pipe and drive it.

 

[mazdarichie]

Can't sell it. Not in a good financial situation right now. Got to figure this out. Plus, I promised my daughter she could have it for her first car when she turns 16. That is 2 years from now. She reminds me all the time.

 

[jdwk]

Well I have this one:https://www.amazon.com (commissions earned)

That one can display live data. I had one similar to that while I waited on my BT one to get here from Hong Kong. You should be able to go to live data and select which PIDs to display. Keep the list short and they update faster. Look for STFT and LTFT. If they aren't labeled, you can look up their PID on wikipedia or the OBDII site and enter them in manually.

STFT is short term fuel trim. If it is positive, it is adding fuel because it is seeing a lean mixture from the primary O2 (you can display the O2 voltage as well). If it is negative it is pulling fuel because it thinks it is too rich.

Same goes for the long term fuel trims. Every few seconds you should see the STFT go to zero and that number get added to the LTFT.

If you are sucking in unmetered air somewhere, the trims will get very positive > +15% because it has to add a bunch of fuel to compensate for the unmetered air to stay stoich.

If it is stable and low <10%, then it is probably not a vacuum leak and more likely related to the ignition.

 

[mazdarichie]

Thanks for the info. I will give it a try and see how it goes.

 

[mazdarichie]

STFT is -3.9 LTFT is 25 those are the readings with the car warmed up and at idle around 750. The STFT seems to go more negative with more throttle.

 

[jdwk]

The long term is 25% which is the highest it will go. You're STFT is negative meaning that it is able to reach a rich condition and the O2 sensor isn't bad. There is almost certainly a vacuum leak going on and is pretty big.

As you open the throttle the vacuum decreases along with your unmetered air, so the 25% LTFT no long applies and it has to pull fuel, which makes the STFT increasingly negative.

I know it sucks and you've tried the carb cleaner trick, but you need to go through every single vacuum line connected to the intake manifold and make sure they are all connected with no cracks. Also makes sure your filter or airbox is sealed tight around the intake piping, and all intercooler pipes are air tight as well. It could be the IM gasket but I think it would have to be a bigger leak for the trims to require 25%.

Just as a sanity check, is the car's fuel control here 100% stock? No piggbacks or O2 clamps and sims?

Also what is the history of the car? Did you buy it used and when? What mods were on the car when you bought it, what have you added? When did it first start running poorly and throw the code?

Tell your daughter not to worry, we'll definitely nail this within two years.

 

[mazdarichie]

I bought the car brand new. No mods at all. Stock. Car started to have a problem once in a while with the idle probably at least 4 years ago. It would just sporadically stumble but that was it. It happened really far apart. It's been almost a year now since it finally threw the check engine light for the first time telling me bank 1 was running lean. Still the only code it throws. Since it started throwing the light it has been running rough and it seems to be getting worse.

 

[jdwk]

I've replaced a bunch of the rubber lines over the years that have cracked. That would be a safe bet.

Since the trims go negative when you open the throttle it kind of rules out a pre-throttle leak, so your intake and IC piping is probably ok.

It seems like there are a lot of hoses at first, but once you understand what they all do it doesn't seem so daunting.

If you don't have the service manual, they are available here http://www.mazdaspd.com/manuals.html

Go to Engine, intake-air system to see the diagrams and troubleshooting.

 

[mazdarichie]

I will get into this weekend when I have time. I don't fear it. I don't mind tearing it apart. I just was hoping I did not have to do that and it would be a easy fix. But with this car it does not seem like it wants to make solving this problem easy.

 

[Flspeed]

Injector is sticking closed or open. When the engine warms up the injector components expand a little. Run some seafoam through the vac system and in you fuel tank.

 

[mazdarichie]

How do I run seafoam through the vac system? Fuel tank is obvious. I will try anything at this point.