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Discussion Starter · #1 ·
Hello,
First let me give many thanks to the folks who contribute to this web site. I’ve found plenty of great advice for my vehicle here. I have also searched as best I know how, the topics that address my concern. I have found a few that are close to my problem but none that match that I can see- at least not any with a solution applicable to me.
I have a stock 2004 Mazda 6 sport wagon (48k) AT, that is missing/ hesitating in certain situations. It started about three weeks ago and I noticed it only when cruising in 5th gear and giving it just a little bit of extra gas in order to get up a hill or to merge. It seems to do it in other gears now and usually at or below 2k rpm.
When I put the car in it’s semi-manual mode, I usually like to shift between 3-4k and the problem is not evident there, but when in automatic, the car will be in 5th, travelling 40 or even slower, and at or below 2k rpm- it is then when I apply a moderate amount of gas that the stuttering and often bucking will take place. I’d never noticed before the problem started but that seems a bit low MPH and RPM to stay in 5th? Anyway . . .
I have tried a few things like running 44k and Seafoam through the tank which did not help. I then did an oil change, air filter change, MAF sensor cleaning ( I was later told a ‘no-no’) that seemed to at least change the “feel” of the problem but it was still there. I partly attributed the change in feel to the fact that I disconnected the battery and thus the computer was relearning. . .
I then changed my plugs (not wires). While the manifold was off I inspected the PCV valve which, as explained in a different thread, was faulty since I could blow through both ends. The dealer didn’t have it in stock so I put the Purolator inline fix described by 84 Fordman with the stopping airflow towards the manifold. I looked at the EGR stem and wanted to cut it but stopped short and instead just cleaned it.
I reassembled and took it out on the road and was happy to find my problems were gone. I was feeling pretty proud of myself for about 2-3 hours of driving time when ‘BOOM’! Back with a vengeance was the stuttering and hesitation and now some missing at idle thrown in now and again. I have not scanned for codes and haven’t had any CEL (unless the bulb is out). The dealer wants $100 for a scan and I went to a local garage and they said, “No CEL? No codes. Don’t bother with a scan.”

I’m hoping I might get some ideas about where to look next . . . Throttle body?

Thank you
 

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sounds like your transmission is about to take a dump
 

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Dude.... I have the SAME FREAKING problem!!!!!!! Unfortinatly I can't identify the source.... I doubt its the transmission (i have 80k on mine and have had 2 tranny flushes, one recently so the fluid is good) Supposudly its the Throttle body. However my problem didnt start until I got the plugs replaced. When im home over the xmas break I will try and clean the TB w/ TB cleaner. Its worth a shot....
 

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QUOTE (fly757 @ Dec 2 2008, 11:01 AM) index.php?act=findpost&pid=1484080
I remember reading about throttle bodies going bad. It would cause bucking issues, and uncommanded changes in power. Just another possibility.[/b]
Unfortunatly my car isisnt under warranty and $300 for a TB that "might" fix the problem isisnt exactly what I want to spend. I am also going to try a PCM/TCM update, that might help alleviate symptoms.


The bummer is I just paid of my car 2 days ago :(
 

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I'm experiencing the same phenomenon, only I have a 2005 3.0L MTX. My issue is under 2K (for instance, pulling from a stop sign in 2nd). I get bucking/missing, but no CEL. I'm befuddled. With 60K on the clock, I'm not inclined to feed the dealer to figure out the problem. A thought did occur to me, however. Since it feels almost exactly the same as the TCS cutting power as rudely as it does, could it be the TCS itself (or perhaps a wheel speed sensor)? Another angle...




:bulb: :wacko:
 

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When I'm home over the holidays I will get my TCM/PCM updated, I think that is the culprit and heres why; The tranny computer is very hesitant to drop gears upon acceleration when the load level is light, so instead the pcm should be openening the throttle more (make use of the TQ converter and all). Instead it's almost like getting a race condition and the system gets stuck in a bad loop. That could explain why it only happens under light load conditions.

GerryB,

I doubt its the TCS, although I see your logic, I will try driving w/ TCS always off to see if the problem still occurs. It also seems to happen more when its warmer out (albeit it still happens even when its 30). Also since you have an MTX it makes me wonder if you have a similiar but diffrent issue. I would try the PCM update, it sounds more like your car is stalling out...
 

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Discussion Starter · #9 ·
I did TCS on/off. No difference. I'll be delving into TB in the next day or so but I too don't want to drop the $ for a "maybe". Dealer asks $300 but I saw one here ..

http://stores.cherry-auto.com/Items/FD-60922 (not sure I'm allowed to post this link, sorry)

Anyone know if this would be safe to use?

Obviously I'm new here but from what I've read thus far on these pages, there is a member who sells an optimized TB perhaps even for less than the dealer price for a replacement.
 

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I had this same issue. I replaced the plugs and it stopped for a while and now only happens very rarely at stop lights. I'm sure this wasn't the tranny since it would happen in neutral. Someone on the forums did mention a faulty TB as the culprit. I can't quite figure out how the TB would make the engine drop below idle.

It feels like a misfire but it would've thrown a code.
 

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ive been having the exact same problems on my 03 with 70k miles. feels like a misfire when idling and below 3000 rpm. i thought i read somewhere that someone had their fuel pump replaced and it fixed it but im not sure. im going to replace my plugs and see if it helps at all, and if i have to ill do the TB as well.
 

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I have the Optimized TB and i still have hesitation issues (happened a while after installing the TB) i replaced the coils (with snipers), i have pulstar plugs (which i still have suspicion) and i just replaced my 2 main Cats (not the pre-cats YET!)

after replacing the cats the car initially felt great and had more pep then before, though on the way to work i got the hesitation and stutter again.

I do however get a random misfire cell, but never when i feel the hesitation. i'm gonna have to replace the pre-cats as i really think that is the culprit. but we'll see
 

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Lately this has started to happen to me to. Symptoms as most describe... only at low rpm, get this stuttering/hesitation feeling. But if you push the pedal down to get higher RPMs, it goes away. Not the cats since I have headers, and not the transmission since an MTX. No cels either, so I doubt its a misfire.

It may be a dirty MAF sensor so I might try cleaning it and see if the problem goes away.

Another culprit mentioned previously was a bad fuel pump. I vaguely recall the 6 doesn't use any sort of fuel filter, so if it is a fuel pump related, the whole pump has to be replaced... not cheap either.
 

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Fuel pump sounds like a good bet to me. This might all be in my head, but it seems that the problem is the most severe when I'm low on gas (under 1/4 tank). I just got my car back from the body shop on Friday afternoon, and the MAF sensor was one of the things that they replaced. I have not experienced the problem since getting it back, but I also have a full tank of gas right now. I'll keep watching it.
 

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QUOTE (CamryRicer @ Dec 8 2008, 09:42 PM) index.php?act=findpost&pid=1486956
Fuel pump sounds like a good bet to me. This might all be in my head, but it seems that the problem is the most severe when I'm low on gas (under 1/4 tank). I just got my car back from the body shop on Friday afternoon, and the MAF sensor was one of the things that they replaced. I have not experienced the problem since getting it back, but I also have a full tank of gas right now. I'll keep watching it.[/b]
Im not so sure about the low gas theory. It happens to me after I fill up and throughout the tank. I did try a test though... I put midgrade in my car to see if the issue would happen more frequently (not burning the fuel as well so if it is a fueling issue it would be more pronounced) Happens just as frequently though.... Plus they reset the ecu when they fixed your car so its still relearning. Also if it is the fuel pump then why are some going at 40k and others at 80k, and why is it inconsistanly happening?


This leads me back to my theory that the car's ECU and tranny ecu( for autos) needs to be updated. Remeber a idling issue where the car would occasionally go into some weird state and go crazy then stall out the car?? I had this TSB fixed a few years back but its been nearly 3 years since the car had the updates, makes me wonder if the fix wasn't 100% correct.


I will try and get to the dealership some time next week to get a TCM/PCM update, hopefully tht works..
 

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QUOTE (CamryRicer @ Dec 8 2008, 08:42 PM) index.php?act=findpost&pid=1486956
Fuel pump sounds like a good bet to me. This might all be in my head, but it seems that the problem is the most severe when I'm low on gas (under 1/4 tank). I just got my car back from the body shop on Friday afternoon, and the MAF sensor was one of the things that they replaced. I have not experienced the problem since getting it back, but I also have a full tank of gas right now. I'll keep watching it.[/b]

I think youre right about it all being in your head. i experience it throughout the entire tank of gas. i was thinking it could be the pre cats as well but since spidy has headers and still has the problem im thinking thats not it. im leaning towards replacing the fuel pump but want to do it myself. does anyone know if the tank can be accessed from under the back seat?
 

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QUOTE (xxSIRJOExx @ Dec 10 2008, 09:02 AM) index.php?act=findpost&pid=1487676
I think youre right about it all being in your head. i experience it throughout the entire tank of gas. i was thinking it could be the pre cats as well but since spidy has headers and still has the problem im thinking thats not it. im leaning towards replacing the fuel pump but want to do it myself. does anyone know if the tank can be accessed from under the back seat?[/b]
On the hatch (probably same for the sedan), its under the rear passenger seat. On mine, you just unbolt a couple of bolts to the seat and then lift it up.
And yeah, I have headers and so I know its not pre-cats. The fact that it only happens at low rpm but goes away if you mash it, leads me to believe its either throttle body or something in the fuel injection.

Its comes and goes, lately its gone... hmmm.
 

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Spidy,

I see in your sig you have an optimized TB, did you do that yourself or did you buy it from Twowheelin?

Also I question if it is a fuel injector, I've run fuel injector cleaner and wind the engine up to 6k daily keeping it (I hope) clean.

Luckily my parents owe me $300 just enough to buy the optimized TB from cordovamotors. not exactly how I want to spend the cash since I just paid the car off... o well
 

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Discussion Starter · #19 ·
"Its comes and goes, lately its gone... hmmm."

Well, after bringing it to a friends garage last week, he test drove it and tried to get a CEL but no matter how much we pushed the symptoms, the light wouldn't come on. He thought it was some type of
tcm/pcm issue and he printed out some TSB and sent me to the dealer. The TSBs I carried with me indicated the symptoms could take place with or without a MIL so I was feeling optimistic.
At the dealer, I took the tech for a drive and reproduced the symptoms. The TSB were not applicable to me since I was up to date but they did detect a missfire on cylinder 6 and the repair called for replacing the coil and plug. Had them do the work for $290 - ($100 scan, $100 LABOR, $90 coil huh?). Since then, I've been running good. I've been trying to reproduce the symptoms and have not been able to for the past 5 days.
I'm pretty sure that this post I'm leaving will be the jinx needed to return the symptoms on my way into work tomorrow.
I have the paperwork showing the missfire on 6- I wonder why no CEL ? Perhaps eventually it would have lit . . .
 

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QUOTE (smokeU6s @ Dec 10 2008, 07:29 PM) index.php?act=findpost&pid=1488036
Spidy,
I see in your sig you have an optimized TB, did you do that yourself or did you buy it from Twowheelin?[/b]
From Two Wheelin... but I've had it for a long time. Only recently did it start acting up, so its got nothing to do with the bored throttle body. I still have my old one so I could swap it back in to make sure its not a throttle body issue. But the hesitation is gone lately so I'll wait till its more consistent.
 
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