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Discussion Starter #1
I was hoping for some input from people with higher mileage 6's. Mine is currently approaching 160k while it doesn't seem to have any issues is there anything I should start to worry about? The only thing I haven't done is eliminate the pre cats because I'm afraid of breaking off the rusty studs in the head. And I suspect my A/C compressor might be starting to fail. I have deleted the egr tube. The car is a 2007 3.0 V6 with the 6sp auto Aisin trans.

Things I have already done/do:

Spark plugs/ coils

Flushed ALL of the fluids ATF, PS fluid, Coolant, even the brake fluid

Regular oil changes with full synthetic high mileage oil with Hy-Per lube

water pump

cam seal

front crank seal

serp belt

idler pulley


Thanks for any input.
 

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At 200k, my radiator split and the rear cat on the rear header gave out. Also typical suspension replacements as tie rods and control arms. My engine and trans were still going strong at 245k when it was recently rear ended and totalled.

Sent from my SM-N950U using Tapatalk
 

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I work in a pretty big Mazda dealership. The most frequent problems we see with higher mileage 1st gen cars are lower control arms and catalytic converters. By and large, it they have been maintained well, the engines are good for well over 200,000 miles.
 

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My car has 270,000KM (about 167,000 miles) and it still runs so strong and gets awesome gas mileage. My only real issue is rust. I'm replacing my rear quarters this winter and I plan on driving my car till it cannot be driven.


Just keep maintaining it, they do run a very long time when taken care of.
 

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Discussion Starter #5
So far it seems like I definitely need to gut my pre cats. I have already had control arm issues on the driver side I have the ones for the passenger side I just haven’t done them yet. @b1lk1 I too am battling rust on my rear quarters and the bottoms of my doors. As far as maintenance I service everything on or usually before it’s recomended interval. I’m no stranger to high mileage vehicles they just all seem to have odd things happen to them, we had a 98 ram 1500 sport that needed rod bearings at 215k a suburban that had to have a fuel pump and an alternator at 220k and then I had an Audi A4 that needed a turbo at 185k.
 

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Gutting the precats is a guaranteed check engine light. I'm hoping that after I replace the converters in the CPE y-pipe that I can get my light off long enough for an emissions test. Only real way to keep the light off is new precats.



I bet there are TONS of good 6's in many scrapyards that simply need new converters.
 

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Gutting the precats is a guaranteed check engine light. I'm hoping that after I replace the converters in the CPE y-pipe that I can get my light off long enough for an emissions test. Only real way to keep the light off is new precats.



I bet there are TONS of good 6's in many scrapyards that simply need new converters.

I know this well


I did all my front control arms, inner and outer tie rod ends and motor mounts for a massive improvement.
I say take care of things as they arise and keep on your preventative maintenance.


The only other things that occurs to me would be the timing cover seal. Mine leaks and other frequently have this issue as well. I recently used Lucas oil stop leak (1/2 recommended amt) and it worked great on the cover seal.

I have also had to replace all the idler/tension bearings and I think the bearing on the AC clutch is going wince it whinnies nearly every cold start for about 1 second.
 

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Discussion Starter #8 (Edited)
A CEL is not a big deal for me (while it will be annoying to look at) I do not have emissions testing where I live. I have looked at headers but the only ones I can find have been ridiculously priced.
 

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Discussion Starter #9
@b1lk1 I just noticed in your sig it said 3.7 tb. I haven't seen anything on this mod yet is it worth doing, and if so what all needs to be done to do it?
 

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A CEL is not a big deal for me (while it will be annoying to look at) I do not have emissions testing where I live. I have looked at headers but the only ones I can find have been ridiculously priced.
The CEL will be on because deleting your precats will mess up the A/F ratio. You'll be running rich losing power and wasting fuel. The CEL for this situation is more than just a eye-sore orange light on your dash. My suggestion would be to replace the cats with a straight pipe at a muffler shop (the big open cavity of a gutted pre-cat will cause unwanted turbulence) and then get an ECU tune which will increase performance and remove the CEL. Or, like @b1lk1 suggested, go to a junkyard and pull some off another first gen. Clogged/faulty cats are often the result of a car either running overly rich or burning excessive amounts of oil. If you are consuming too much oil, switch to a thicker weight or something higher quality that won't burn as much. Be sure to check the car for codes in case you have a faulty injector or something causing the engine to run too rich.

Lower control arm failures are the result of two things. 1: Aggressive cornering, and 2: Rough, bumpy roads. It's not actually the control arm that fails (Unless your arm has physically snapped in half.) It is typically the ball-joint which becomes worn and starts to cause play. As cars became newer, manufacturers started to look for ways to cut costs with their parts so control arms and ball-joints are now integrated into one. You can check if your ball-joints are worn by lifting the car up in the car and taking a crow-bar to the arms. If the ball-joint is allowing your control arm to wiggle around, even just a little bit, you need new control arms. Replacing then will noticeably firm up your suspension and make the car drive better.
 

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Discussion Starter #11
The CEL will be on because deleting your precats will mess up the A/F ratio. You'll be running rich losing power and wasting fuel. The CEL for this situation is more than just a eye-sore orange light on your dash. My suggestion would be to replace the cats with a straight pipe at a muffler shop (the big open cavity of a gutted pre-cat will cause unwanted turbulence) and then get an ECU tune which will increase performance and remove the CEL. Or, like @b1lk1 suggested, go to a junkyard and pull some off another first gen. Clogged/faulty cats are often the result of a car either running overly rich or burning excessive amounts of oil. If you are consuming too much oil, switch to a thicker weight or something higher quality that won't burn as much. Be sure to check the car for codes in case you have a faulty injector or something causing the engine to run too rich.

Lower control arm failures are the result of two things. 1: Aggressive cornering, and 2: Rough, bumpy roads. It's not actually the control arm that fails (Unless your arm has physically snapped in half.) It is typically the ball-joint which becomes worn and starts to cause play. As cars became newer, manufacturers started to look for ways to cut costs with their parts so control arms and ball-joints are now integrated into one. You can check if your ball-joints are worn by lifting the car up in the car and taking a crow-bar to the arms. If the ball-joint is allowing your control arm to wiggle around, even just a little bit, you need new control arms. Replacing then will noticeably firm up your suspension and make the car drive better.
Let me start by saying that I feel like you are suggesting that I am a complete idiot and know absolutely NOTHING about cars and quite frankly that's pissing me off.

First I and most people who regularly work on their own cars know how to check ball joints. I'm sorry I was not specific enough for you but when I referred to control arm problems I meant worn out ball joints which if you read my entire reply I mentioned I replaced.
Second I'm not sure where the oil burning part came from because so far no one here has even mentioned that. I was losing oil because my crankshaft seal was worn and leaking, my car actually burns little to no oil at all, surprising for an 11 year old car with 157,00 miles on it.

Finally myself and many people I know have gutted/removed their cats and have NEVER had an issue with AF ratio. I just did it last week on an 07 charger patrol car. By the way @b1lk1 was saying that he thinks that there is a large number of 6's that were scrapped when they just needed new cats.

Please completely read ALL of the posts.
 

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Let me start by saying that I feel like you are suggesting that I am a complete idiot and know absolutely NOTHING about cars and quite frankly that's pissing me off.

First I and most people who regularly work on their own cars know how to check ball joints. I'm sorry I was not specific enough for you but when I referred to control arm problems I meant worn out ball joints which if you read my entire reply I mentioned I replaced.
Second I'm not sure where the oil burning part came from because so far no one here has even mentioned that. I was losing oil because my crankshaft seal was worn and leaking, my car actually burns little to no oil at all, surprising for an 11 year old car with 157,00 miles on it.

Finally myself and many people I know have gutted/removed their cats and have NEVER had an issue with AF ratio. I just did it last week on an 07 charger patrol car. By the way @b1lk1 was saying that he thinks that there is a large number of 6's that were scrapped when they just needed new cats.

Please completely read ALL of the posts.
I think it's fantastic that you know your cars, but I was obviously speaking on the behalf of other people checking this thread who are not so humbly knowledgeable about cars like you are. You're not the only one reading this thread.

The thing about the AF ratio has more to do with deleting your main cats rather than the pre-cats (which are more used to control start-up emissions) but since you are getting a CEL even from removing pre-cats, obviously the car will not be running optimally.

How much oil a car burns has little to do with it's age or mileage. It's mainly a factor of how the car was treated when brand-new. A car that wasn't broken in carefully when the engine was brand-new is more prone to consume oil right from the start and will only get worse as it ages since the valve stem seals and piston rings continue to deteriorate. Other things such as a failing PCV valve (common on the 3L V6 with higher mileage) can also cause increased oil consumption.
 

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Discussion Starter #13
Let me start by saying that I feel like you are suggesting that I am a complete idiot and know absolutely NOTHING about cars and quite frankly that's pissing me off.

First I and most people who regularly work on their own cars know how to check ball joints. I'm sorry I was not specific enough for you but when I referred to control arm problems I meant worn out ball joints which if you read my entire reply I mentioned I replaced.
Second I'm not sure where the oil burning part came from because so far no one here has even mentioned that. I was losing oil because my crankshaft seal was worn and leaking, my car actually burns little to no oil at all, surprising for an 11 year old car with 157,00 miles on it.

Finally myself and many people I know have gutted/removed their cats and have NEVER had an issue with AF ratio. I just did it last week on an 07 charger patrol car. By the way @b1lk1 was saying that he thinks that there is a large number of 6's that were scrapped when they just needed new cats.

Please completely read ALL of the posts.
I think it's fantastic that you know your cars, but I was obviously speaking on the behalf of other people checking this thread who are not so humbly knowledgeable about cars like you are. You're not the only one reading this thread.

The thing about the AF ratio has more to do with deleting your main cats rather than the pre-cats (which are more used to control start-up emissions) but since you are getting a CEL even from removing pre-cats, obviously the car will not be running optimally.

How much oil a car burns has little to do with it's age or mileage. It's mainly a factor of how the car was treated when brand-new. A car that wasn't broken in carefully when the engine was brand-new is more prone to consume oil right from the start and will only get worse as it ages since the valve stem seals and piston rings continue to deteriorate. Other things such as a failing PCV valve (common on the 3L V6 with higher mileage) can also cause increased oil consumption.
As I said that’s just the way I took it, maybe if you don’t want people to assume that’s what you’re saying you should try wording your posts differently so you don’t sound so condescending. You do realize that you said that “oil consumption has little to do with age” and then said that “as an engine ages the valve stem seals and piston rings deteriorate with age”? And that those completely contradict each other. I did replace my pcv and fortunately I don’t think this car has had an issue there because when I had the intake off to do the plugs and coils there was almost no oil residue at all inside of it.
 

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As I said that’s just the way I took it, maybe if you don’t want people to assume that’s what you’re saying you should try wording your posts differently so you don’t sound so condescending. You do realize that you said that “oil consumption has little to do with age” and then said that “as an engine ages the valve stem seals and piston rings deteriorate with age”? And that those completely contradict each other. I did replace my pcv and fortunately I don’t think this car has had an issue there because when I had the intake off to do the plugs and coils there was almost no oil residue at all inside of it.
I don't mean to condescend to anyone at all. That isn't what I intended.

I meant things such as valve stem seals and piston rings deteriorate rather quickly with age IF your engine was not broken in optimally from the get go. If you are dealing with an engine that was well sealed since brand new (like in your case) Those seals will stay solid for a very long time. I had a 1995 Nissan Maxima with 220,000 Miles on it that didn't burn a drop of oil - this is a great example of what I mean.
 

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This went south quick...

With regard to exhaust changes...
Air/Fuel ratio will only be changed by the upstream O2 sensors (the ones before the catalyst). The Oxygen sensors after the catalyst are only there to let the PCM know that they (the upstream catalytic converters) are functioning properly. A check engine light that illuminates as a result of "cat gutting" is because the downstream oxygen sensors (sensor 2) are registering too many inversions (and therefor a damaged catalyst) as a result of the catalyst material being removed.
People have tried pulling the downstream O2 sensor out of the exhaust stream to try and mute the reading or by adding a device that sends the appropriate signals for the computer to think it is working properly.
The 1st gen used a 4-wire O2 sensor and the life of that sensor (according to NTK (the OEM supplier)) is 100,000mi. After that time interval they become slow to respond and will not adjust the air/fuel ratio as quick. This degradation may or may not affect the combustion and therefor catalyst health.


Engine operation is affected by back pressure and reducing that pressure may change how your exhaust valves close. This could (in some vehicles it does) change how the valves seat and therefor wear. I have never heard a single instance of reducing back-pressure with a higher flowing exhaust affecting the 1st generation Mazda 6 (Duratech) motor in this manner.


If you gut your cats you will likely produce a check engine light but your air/fuel ratios will be unaffected.
 
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