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Discussion Starter #1
Just moved across country from California rode a bike since I could lane split. Now in Florida needed a car.

Guy from work had a 2004 Mazda 6 2.3 automatic with 170k. Not a car guy and kept having problems gave up on it and said I could have it for 200 bucks.

Went and looked at it. Read codes. Misfire cylinder 1. Changed spark plugs. Code came back. Changed wires. Code came back. Change coils. In business! Best 200 bucks ever.

However seems to have another few issues.

No codes. Some times it idles and sounds rumbly inside the car. Like annoyingly kind of bassy. Outside doesnt sound so bad.

Replaced air filter, cleaned maf sensor, and cleaned throttle body.
Ecu reset and still happens from time to time cold and warm start. And when sitting in traffic.

Other issue is down shifting.

I usually have to do 25 mph on a military base.
As I accelerate to 25 I make it up to 3 but when I let off the gas the car shifts into 4th. As the car drops in speed and I press the gas but the car stays in forth gear. The car will not drop to third gear until the car is just below 20mph. If I mash the petal it will shift into 2nd but this is not really practical for cruising.
I changed the transmission fluid. Well as much as I could last night. Car seems to shift a little smoother but still when I decelerate the car stays in 4th until under 20 and will only down shift when the gas is mashed and the rpms shoot up past around 2500 to 3000 rpm. If I just smoothly apply pressure. Its just boggy until it reaches higher rpms.

I have a speed sensor on its way but I don't want to sit here and throw parts at the car. And hope they work. I have been trying to find stuff but I have only found two other post on the internet that describe what my issue is and they had no responses.

Any help in the right direction is much appreciated.
 

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So I picked up a speed sensor off of amazon. It sayed that it wasnt applicable to my car but it was for like a protege and a 3 and only worked on my car for 2006 and up. With one day shipping I said wth its only 13 dollars. Defiantly some cheap Chinese stuff. Anyways. I put it in and at around 25 it shifted into 3rd gear. Still can be sluggish being in 3rd around 20 mph but I'm wondering if I fork out for one that says its an exact fit if it will fix my problems
 

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Congrats on the find. When I bought mine I ended up replacing the trans fluid 3x to get the majority of it fresh. In my case it solved my shifting problem.
If you noticed a difference with the speed sensor it could be a result of not being vehicle specific and it may make a difference but still seems like a gamble.
My 5 speed wants to be in 5th at just over 30mph (~1600 rpm) if I am very light throttle. In my case the trans is responding to degree of throttle opening and speed of accelerator pressure.
If you have the 4speed (FN4A-EL) then your shift point sounds about right.
Shift Diagram FN4A-EL (4spd ATX).jpg

The rumbly sound could be a heat shield that is vibrating. Perhaps some of your motor mounts are bad and allowing more engine movement than normal.

Anyhow, good luck.
 

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Thanks for the input. Yeah I'm kind of nervous about the sensor so I have a specific one on its way. As well as a throttle body. I took it out again and cycled it and seemed like it was rubbing on the bottom. Tried to remove the plate but the screws just wanted to strip. I'm gonna do some more fluid changes too.
 

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In regards to your continuing rough idle, I know the V6 had tons of issues with the PVC, but someone will have to verify if it can contribute to the same issues in the 2.3L - regardless, here's a quick little write-up about replacing it: How to : PCV Valve removal
 

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Discussion Starter #6
I did watch a video on a 3 about a dirty pcv. I took mine out and sprayed some maf cleaner into it. I'll replace that too. Cant hurt and there not too expensive.
 

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Had a new pcv on amazon. Same day delivery for 30 bucks. Hope this solves the issue and I can maybe save some money by canceling the new throttle body. Wish me luck.
 

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Well I changed pcv. Car is driving a lot smoother but still has a shaky idle defiantly when the ac or fan kicks on. My throttle body will be here tomorrow. I'm really hoping that it will be the final thing to make this a normal feeling vehicle. But man the car does a whole lot better just normal cruising.

If that doesn't do it I'll probably be onto some motor mounts. I just think the throttle body tho cause its not bad at cruising and the rpms are sluggish when letting off the gas petal
 

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Well I changed pcv. Car is driving a lot smoother but still has a shaky idle defiantly when the ac or fan kicks on. My throttle body will be here tomorrow. I'm really hoping that it will be the final thing to make this a normal feeling vehicle. But man the car does a whole lot better just normal cruising.

If that doesn't do it I'll probably be onto some motor mounts. I just think the throttle body tho cause its not bad at cruising and the rpms are sluggish when letting off the gas petal
Great. Glad to hear it's doing better. Keep in mind it is a 16 y/o 4cyl creeping up on 200,000mi with the older 4speed automatic. It was never going to move like a scalded dog....

Did you check the intake accordion hose for cracks? You have to look down between the pleats to be sure. Mine was toast at 120,000 mi.
 

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^^^ I'm with him. Glad the PCV helped a bit and hoping the TB helps even more, but you'll likely never get the thing running flawlessly.

Check that accordion for sure and keep us up to date.
 

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Lot of good ideas I see here. But one I don't see is checking for vacuum leaks. A vacuum leak can cause the symptoms you are describing. Since it is a 2004 and the previous owner was not a 'car guy', there are old and probably cracked vacuum hoses that will leak. The first thing I recommend is visually inspecting all of the hoses, especially the ends. Pull an end of the hose off and squeeze and roll between your fingers. If you see little cracks, replace the hose. Your replacement of the PCV valve and having that improve performance tilts me in this direction. If this iteration doesn't quite solve the problem. Do a smoke check of the vacuum system. This will give a definite indications of the integrity of the system. You can consult YouTube on how to make your own smoke tester inexpensively (old jar, rag soaked in mineral oil, soldering iron, things you probably have around the house). There are also videos on how to leak check using other techniques such as a spray (aerosol). Checking the vacuum system is an inexpensive way to verify the integrity of a system that plays an important part in the operation of the engine in modern cars. Vacuum hose is inexpensive and validating the integrity of the system will be a lot cheaper than swapping out parts that you think may be a problem.
 

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I've taken the accordion off probally 20 times and looked at it each time that I've taken off everything
Today I finally found the hole.
Don't know If I'm more relieved or irritated.

On the down side I broke the nipple off of one of those solenoid valves one of the two that sit on the engine so that'll have to be replaced.
 

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Glad you at least found something that could be causing it. Let us know how it's running after that.
 
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