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Discussion Starter #1
I own a 2004 Mazda 6s with about 64,000 miles.

Recently, there has been a very occasional, very slight hesitation when accelerating while driving (not from stop). The idle isn't rough, there are no problems starting, there's no check engine light, and the MPG seems to be about the same. In all, except for that very occasional hesitation, the car drives and reacts completely normally.

My first instinct was that I have a fuel filter getting clogged. I've replaced it on cars I owned before 2004, but just discovered that on my 6, a fuel filter problem seems to equal a significantly more expensive fuel pump replacement. Is it worth trying a fuel injector cleaner or would that just make the problem worse by getting more crap in the fuel filter? I'm a little worried about a hard-to-replicate problem might result $600 repair that might not even be the problem.
 

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To answer your question, nothing will clean a fuel filter, with the exception of pumping fuel backward through it...and even that wouldn't be a complete clean. It traps crud until it finally clogs and needs replaced. I changed the filter on my old 92 S-10 and held it upside down to let it drain. I was horrified at what poured out.
 

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Discussion Starter #4
To answer your question, nothing will clean a fuel filter, with the exception of pumping fuel backward through it...and even that wouldn't be a complete clean. It traps crud until it finally clogs and needs replaced. I changed the filter on my old 92 S-10 and held it upside down to let it drain. I was horrified at what poured out.
I do know I can't clean the fuel filter, but I was still wondering if it was a fuel injector problem (I'm not an expert - I can handle small easy tasks but not major ones). My concern was that I'd unclog some junk and if it wasn't the fuel injector, I'd just make the fuel filter problem worse. I'd probably rather bring it straight to the garage, but with a vague problem without a lot of symptoms, I'm a bit concerned about shoveling money into the mechanic's bankd account.
 

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Well, it may end up costing more than you would like it to, but some spark plugs wouldn't hurt. Change the fuel filter, and THEN run some Techron or Seafoam through it.
 

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Well, it may end up costing more than you would like it to, but some spark plugs wouldn't hurt. Change the fuel filter, and THEN run some Techron or Seafoam through it.
Yeah, I don't mind eating some sparkplugs as they're probably getting on a replacement time anyway, I'm just concerned about a speculative fuel pump replacement - changing that is beyond my abilities, so I'm already looking at a minimum of $600 for that. I'll definitely wait and see what they say at the mechanic's.
 

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Well, it may end up costing more than you would like it to, but some spark plugs wouldn't hurt. Change the fuel filter, and THEN run some Techron or Seafoam through it.
The fuel filter is part of the fuel pump. You can't just replace the filter without replacing the entire pump.
 

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DSzymborski- I would just replace your spark plugs first and then see how it runs before you start thinking about needing an expensive repair. You can change the plugs yourself in a couple hours for ~$50. I highly doubt it is your fuel pump.
 

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Discussion Starter #9
Yeah, that's probably what I'm going to do. I've changed sparkplugs before. It didn't even enter my mind - since I'm not a car guy, I go by previous experience and in past cars with bad sparkplugs, I've had rough starting and idling as clues. This was just an ever-so-slight hesitation that happened maybe once per 30-40 miles.

My 6 has been incredibly dependable, so I haven't had a lot of experience at things going wrong in a 6. On my nightmare of a Ford Tempo years ago, for example, I could tell in about 5 seconds when an alternator was just every-so-slightly starting to go.
 

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Like ed4ward1982 suggests, if you have the extra coin, it wouldn't be a bad idea to replace the coils since it is a bit of work to get to the back 3 plugs/coils. I purchased my coils at rock auto for around $35 each. I got the Standard Motor Products coils. They have been great so far. You could put in all new coils and spark plugs yourself for around what a shop would charge you just to replace the plugs.
 

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I haven't had time to change the sparkplugs (I've been sick for about a week). My sister drove my car over the weekend and reported that the occasional hesitation happens roughly at 40 MPH and there is no change in the RPM or slipping to a lower gear, no jerking or any kind of sound or any other change in the car's handling. Could this perhaps be a bad throttle position sensor? And if so, wouldn't this pop the check engine light? Just thought I'd provide a little more detail just in case someone (thanks for the responses again!) had any other ideas.
 

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I haven't had time to change the sparkplugs (I've been sick for about a week). My sister drove my car over the weekend and reported that the occasional hesitation happens roughly at 40 MPH and there is no change in the RPM or slipping to a lower gear, no jerking or any kind of sound or any other change in the car's handling. Could this perhaps be a bad throttle position sensor? And if so, wouldn't this pop the check engine light? Just thought I'd provide a little more detail just in case someone (thanks for the responses again!) had any other ideas.

Did it only happen once? Usually you would get a CEL code..
 

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I had hesitation issues last year and replace my plugs (04 V6) The intake manifold needs to be removed on the V6 to get to the back 3 plugs (I was able to do by just moving without removing) . Be sure you have the right plugs and the gap is correct so you do not have to go back and adjust.

This seemed to take care of the problem, but it returned; this time with a check engine light (misfire cylinder 1). Went back and replaced the plug and coil on 1. Good as new. Moral of the story is that if you can, replace the coils when you do the plugs. If you have to skimp on the coils, just do the coils on the back 3 and do the front 3 when you can

.
 

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I'm having a very similar problem except that my car is bucking and hesitating only under a load and more so between 3000 - 3500 rpm's. It all started with the car running in machine gun mode in the rain last March and found out that I needed a new coil pack on cyl. 6 and my downstream 02 sensor was bad. Replaced the coil pack right away, but waited 4 months to replace the O2 sensor (I know I shouldn't have waited so long, but I have just been so broke. So anyways- now the problem is still there- possibly even worse- & I get the flashing misfire CEL when I'm past the 3,000 rpm's. Had my spark plugs replaced with NGK iradiums (and they changed the intake gasket??). Problem still there and car is driving like shit! So frustrated that I brought it into Mazda and the mechanic there is trying to say that I should replace the fuel pump and I could possibly even need a new manifold converter??!!. . . not just a new cat converter but the whole manifold converter assembly??!! WTF?!

A friend of mine has just suggested that I should start w/more simpler things such as:

1st check their work on replacing the spark plugs and intake gasket;

if all checks out there then He's thinking that I might just need a new fuel filter but I was told by Mazda that there is no separate fuel filter and that there is only the whole fuel pump/filter assembly as one. Is this true?

He steered me away from MAF cleaning/replacing as he thinks my problem wouldn't be as severe as it is under a light and heavy load and the fact that the car idles perfectly fine.

Any thoughts on this? Sorry for rambling on and on- just wanted to be as descriptive as possible. I greatly appreciate ANY feedback
 

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another simple thing, check your intake tube, connected to the TB, some are known to crack. i know how you feel about trying to scrape up money for unexpected stuff for the 6.
 

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I've used a product that works very well and prides itself on cleaning up fuel problems. Goto: order.mysyntek.com and read about it. It's not expensive and they recommend using it for 6 full tanks. Matter of fact, I now am able to drive from Va. Beach to Atlanta on one tank of gas.
 

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