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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #1 ·
Hello everyone,
I have turned to you folks over the years and have never been let down. I am just about to throw in the towel on my 04 Wagon, figures since I just put HID lights in. This always happens to me when I do a non necessity upgrade to an older car...they die right after.

Back story:
2004 Mazda6 Wagon 3.0 v6 5spd auto. Bought 3+ years ago with a misfire. Someone installed Autolite copper plugs in it.
Replaced:
Both warm-up catalysts (pre-cats)
Plugs (Motorcraft)
COP's (United brand)
PVC
Plenum gaskets
Air cleaner
Trans fluid (x3)

Ran great. Lots of power 19mpg average (17-26, town/highway)

Only code since that time is p1410 and it stays.

Currently:
The car has been feeling like it is misfiring in 4th-5th gear (below 2000RPM) Very light throttle
Add throttle and it feels like I am driving on a windy day. Like there is some external force slowing me from outside and it is not regular or rhythmic.
When I start the car after warming up and press the accelerator to go it feels like there is no power. No jerking or stumbling just I have to keep pushing the pedal down and nothing different is happening. After driving a mile it feels normal.
Current Gas mileage 12mpg
So I replaced the Plugs (OEM Motorcraft platinum) x6
Denso COP's x 6
Check all hoses and vacuum lines. All Fine


Drive today: Traveling down a highway, I rarely drive anymore, it was appalling the difference. I used to be able to drive up the hill in 5th gear and 60MPH. I could not accelerate without downshifting but it could hold it. Today I could not do better than 42MPH and it wanted to go to 2nd gear at 5000RPM but then dropped down to 4200RPM. I cannot seem to push any faster than 4000-4200 RPM on flat in 3rd.
Incidentally the car has been smelling like sulfur all the time for around 6-8 months, no matter how hard I drive. Generally I will rev to 4000RPM once or twice a year so not hard. Even on flat highway it wants 4th gear all the time

MIL ON:
p1410 (for some time but does not illuminate MIL)
p0300 (first time ever)
p0302 (first time ever)

Freeze Frame (p0302):
Load% 84.3
Coolant (F) 185
ST FTRM1(%) 0.0
LT FTRM1(%) -12.5
ST FTRM2(%) 0.0
LT FTRM2(%) 13.2
RPM 3187
64MPH
Advance 22 (deg)
IAT (F) 66
MAF (lb/min) 8.213
Abslt TPS (%) 50.5

I have my suspicions as to what it could be but I would love to hear novel ideas.

Thanks for even making it to the end of this post. If you have a response then thanks even more.

Happy Motoring
 

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The sulfur smell would lead me towards your cat. You've replaced the pre cats but perhaps the rear cat is getting clogged. This is just a guess so temper that with your other responses. Don't give up yet, the wagons are a rare breed!
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #3 ·
The Sulfur smell was telling me that the catalyst was overwhelmed. I did not think about the rear cats however.
Addendum. For a while 2 years ago the Spark plug at the #1 position (I think. Pass side rear, bank1) was loose enough to pass gas (he he) and sound but I didn't clue onto it for some time. That was the manifold that I had to extract a stud from and repair so I thought it was an exhaust leak. The smell of raw fuel in the cabin from fresh vent should have clued me in.
Anyways, the coil at that position was badly discolored, both on the boot and the inner conduit. I cleaned it up and moved it forward to #4 (pass side front, bank2) so I could get to it if it acted up but I never noticed anything.

My LTFT1 (bank1/rear) is showing a NEG(-) number indicating rich running. (CMP sensor?)
LTFT2 (bank2/front) is showing a POS(+) number indicating a lean burn. (vac leak, clogged injector, blocked exhaust?)

I don't know what my number should be as I am at work and do not have access to my Manual but I am fairly confident there should not be a 25 point spread between the two.

I will read curves when my new Bluetooth scan tool comes and can tell if there are inversions in the O2 sensors. This will at least tell me if the front cats are involved.

This is the most fragile car I have ever owned.
I'll stick with it for now...unless I find a nice TSX wagon before I figure this out.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #5 ·
It may have something to do with transmission differences, mine being a sluggish automatic, and what is invariably advanced age of the vehicle in general. I have taken it WOT twice both times backing off at 500RPM. The first ended up with oil on the exhaust (from somewhere)and smelly for a bit. The second was recently downshifting to 2nd on the freeway trying to accelerate past 42mph (auto shift in D). Now it is definitely off in power. 500RPM is probably past its functional limit at the current mileage. I suppose this would not make it fragile but rather owner abused. Oops.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #9 · (Edited)
I finally got some more numbers. Incidentally the car will "ping" so bad after 4000RPM while driving I have to back out. I can rev to 5000+ easily in neutral.

Idle:
LTFT1 -12.5
LTFT2 -9.4
MAF (lb/min) 1.75

2500RPM:
LTFT1 -5.5
LTFT2 10.9
MAF (lb/min) 0.54

Exhaust system comes off tomorrow [groan] as right now I am operating under the impression that I have an exhaust restriction.
 

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You might also want to do a compression test before dropping the exhaust. You can also pull both front O2 sensors out and take it for a quick ride and see if there is more power. The bad smell for a prolonged period is not a good sign for the cats. Doing the compression test should be 1st on the list.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #11 ·
You mean exhaust back pressure right? I agree. Seeing if there is excess pressure would be ideal. I am uncertain how pulling the upstream O2 sensors will affect my mixture during the test. Possible damage?
I took the O2 sensor (bank 2) and visually checked it and it looked (okay) even if I couldn't back light it. I realize this will be my only real way of showing restriction since I cant see into the downstream converter for bank 2. My dilemma is not wanting to pay $100 for the equipment to check. How many more times in my wrenching future am I going to use it? although if I keep this car I may get several uses out of it.

Can anyone think why the fuel would suddenly go lean (bank2) after about 1200RPM? And if bank 2 is leaning out (possible obstruction) why would I experience a misfire code on Bank1 (cyl 2)?

My Shop Manual says this: for P0171, P0174 (Fuel system trim lean [RH], [LH])
Misfire
HO2S Deterioration
HO2S Malfunction
Leakage Exhaust System
MAF/IAT sensor malfunction
Air suction in intake system
Fuel Filter clogged
Fuel Pump Malfunction
Fuel Leakage on fuel line from fuel delivery pipe and fuel pump
Pressure regulator Malfunction
Fuel Hose Return Clogged
Fuel Injector Malfunction
VVT control system malfunction
Purge solenoid valve malfunction
Purge solenoid hise improper connection
Insufficient compression
PCM malfunction.

I suppose it is better than not knowing what to do next.
 

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What about the air intake rubber hose that connects to the throttle body? If that is broken it can cause all sorts of ailments.

Yes, I meant pulling the O2 sensors to do an excess backpressure test the backyard way.
 

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What about the air intake rubber hose that connects to the throttle body? If that is broken it can cause all sorts of ailments..

I would agree if showing lean, that this would be the first place to check.


Scott
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #14 ·
That accordion hose is pretty much shot but my repair was through. Gorilla tape for strength under and about half a roll of stretched electrical tape.I did just check it on your suggestion but it has been holding strong for years. Still looks plenty sealed. You cant even tell unless you look close.
That air hose is common to the plenum, both banks. I can't figure how it would only affect one.
I am going to go with b1lk1's suggestion once my body aches let me. My fever broke so maybe today. My brain can still wrap around the possibility of a bank 2 restriction. This manifests as enough back pressure the computer see it and switches the fuel curve for that bank from rich to lean.
These cats were melted when I bought the car. The pic shows what came out of the rear bank. What was in the front bank??? I couldnt see the cat and there wasnt much that dropped out when I removed that front manifold but...
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #15 · (Edited)
Update:
Cleaned MAF/IAT, CMP1 (522 Ω), CMP2 (542 Ω ), CKP (293 Ω) All within spec, but a bit dirty.
Intake vacuum test shows 17 in Hg at idle and 18in Hg at 3000rpm - restriction unlikely

New Values

Idle:
LTFT1 = -8.6
LTFT2 = -3.1

2500rpm:
LTFT1 = -5.5
LTFT2 = 10.9
 

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Have you done a compression test yet? To me that is the logical next step..
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #17 · (Edited)
Have you done a compression test yet? To me that is the logical next step..
I checked the resistance on the starter when cranking and it shows even resistance over the whole crank cycle. I have not done a plug out trial of that test however.

I suppose a 15% change in mixture is within specifications. Maybe I am just need not perceverate on this and look elsewhere for my pinging/power/gas mileage issue.

Thanks everyone who has been sending ideas. I would love you all to keep them coming.

EDIT: On further thought I realized that a more accurate compression test would be in order. I tried both of the compression test kits that Harbor Freight sells and neither fit. Does anyone know for sure of a brand of compression tester that will fit the 3.0 v6?
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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3,851 Posts
Discussion Starter · #18 · (Edited)
UPDATE : PROBLEM SOLVED

Summary: Loss of power, P0300 and random P0302, P0304, etc... Felt a misfire at low RPM (<2000RPM) light throttle, surging in 4th and 5th gears (ATX), pinging beyond 2500RPM under moderate acceleration, low MPG (12 mpg city).

I finally got a scan tool that interfaced with my laptop and was able to read wave forms. The downstream O2 sensor in bank 2 was reading flat
(nearly... 0.02V) and smooth in curve. I bit the bullet and ordered all four catalytic converters and all four oxygen sensors. After installing them this weekend I must report that Mozzie is back like I have never felt. This fix has eliminated all surging, rough idle, low MPG, and loss of power. Starts are faster and exhaust sounds better. Ladies and gentlemen, I am in love again (and that's saying a lot since it is an automatic).

What I learned. When I replaced the melted pre-cats (Three-way catalyst/warm-up cats) four years ago I did not also do the downstream converters or the oxygen sensors. The condition of the catalysts was nominal at best and it contributed to an increased back pressure that reduced my ignition efficiency. This reduction in combustion (sub-clinical misfire) resulted in increased temperature due to nu-burnt hydrocarbons and caused the "new" pre-cats to fail along with the downstream cats. Whether the downstream catalytic converters failed completely and thus precipitated the failure of pre-cats is unknown. Regardless, after inspection, they are all plugged (the exception is rear manifold which is still open). I wasted $700 on pre-cats when I did not buck up and do the whole thing. This says nothing about working on the garage floor (albeit on cardboard) in the middle of what had been a solid winter here in the NW. Lesson learned. Don't be cheap! Dealer wanted $7000USD (2017) to replace all 4 cats and O2 sensors.


I want to thanks everyone who gave me input. Your feedback (esp Scott with the "...don't give up") spurred me on.
 

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Wonderful news and great information for the archive here on the board! Thanks for posting it up.

I've always been a bit dissappointed with my fuel economy. I check it regularly and haven't been above 24.6mpg yet. I've seen others report 28 (IIRC) and your post makes me wonder if the cats play a role there. What do you think?
 

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Glad to hear you saved it ! Hate to see them go to the scrap yard just because the owner didn't want to do CPR (spend some time and money) on them. :smile2:

For future reference, please post where you order from and if you don't mind, share how much you paid for all of it.
 
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