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#2592 of 2858 2009 Mazda6 slight knock at idle
Dec 18, 2009 (8:48 am)
I made a few more observations regarding the slight knock at idle that I am getting.
The knock intensity varies from day to day. On humid and rainy days it is almost eliminated completely. The drier the weather the more pronounced it is.
Also as you step on the gas it disappears, so to me this means it is not related to any real malfunction in the car such as bad bearings or valves or anything of the sort. I think it is basically a fuel combustion issue. It is what is called detonation, and I know that moisture (Water vapor) reduces detonation. The reason might be fuel injector related, spark plug related, or simply because the car is tuned by Mazda to run too lean at idle. This means not enough gas is being pumped into the engine at low rpm.
Now I plan to replace the plugs, but is there also a way I can somehow increase the fuel delivery at idle, such as a fuel pressure regulator, or is it all controlled by the ECU these days?
#2593 of 2858 Re: 2009 Mazda6 slight knock at idle [jkobty2]
by Mr_Shiftright HOST
Dec 18, 2009 (10:46 am)
You wouldn't get denotation at idle, though. That's strictly an engine-load related problem.
Piston slap is a possibility, as this can be due strictly to the use of a short-skirted piston. Some new cars exhibit this. GM and Subaru products have had this "problem" (which is really harmless in this case). One gets better combustion on humid/wet days, so that would drive the piston a bit harder.
#2594 of 2858 Knock at idle
Dec 18, 2009 (9:39 pm)
I am familiar with piston slap, that sound usually occurs when starting a cold engine and persists for about a minute or less, then as the pistons expand, the sound disappears.
What I am experiencing is exactly the opposite. The engine is very smooth when cold, The sounds I am talking about do not start till the engine has warmed up completely. The engine stays smooth until it reaches the full operating temperature (temperature gauge in the middle). After the engine is fully warmed up, then it starts exhibiting the knock sound at idle, and a slight tapping sound on very light accelerating. Above 2000 rpm it runs just fine. That is why I am thinking it somewhat related to combustion. Since when the engine is cold, the computer pumps more gas into the cylinders, and hence no bad knocking. As the engine warms up and starts running leaner on gas, that is when the sounds start.
#2595 of 2858 Re: Knock at idle [jkobty2]
by Mr_Shiftright HOST
Dec 19, 2009 (10:27 am)
Okay, but you can't have detonation at idle speed. The engine would destroy itself, even if this were possible. Have you considered wrist pin noise? This can be tested by disconnecting one cylinder at a time---if the noise suddenly doubles in frequency, that wrist pin is loose.
Let's see---other noises can be: fuel injector clicking; exhaust leak, valve tappet, worn camshaft lobe.....???
What I'm driving at is that the only kind of noise that might appear when the engine is warm and not cold is one related to the thinning of the oil.
Anyway, I wish I could hear it, I could talk more intelligently about it.
#2596 of 2858 Re: Knock at idle [Mr_Shiftright]
Dec 19, 2009 (12:49 pm)
Ok, I will try the spark plug test.
I will also try to get a video with sound uploaded.
#2597 of 2858 Engine was running fine now instantly stopped cranking!
Dec 31, 2009 (12:42 pm)
I have a 2006 Mazda 6 4 cyl. It was running fine. I came back from the holidays at home and unloaded my car. 2 hours later I went to run to the store and it wouldn't crank. At all. It tries really hard and sounds healthy, but it just won't start. The turnover sounds fine and the lights are all fine so I'm guess it's not the battery.
Someone suggested spark plugs, but I doubt they'd all go out at the same time. Someone else suggested fuses, but I couldn't find any that were blown.
Someone else suggested security system and to reset it, but I can't find out how to do that for the life of me!
#2598 of 2858 clutch shudder
Jan 12, 2010 (7:25 pm)
Well, my wife brought in my 04 mazda6 wagon in for service today. 63800 miles. Asked them to check out the clutch, since it has been shuddering when I shift from 1st to 2nd unless I give it more gas than usual. The response she gets is that the pressure plate is getting weak--it will likely be driveable this way for a while--and then I will need a new clutch to the tune of $1750. I am 43 years old, drive the car sensibly, and have never worn out a clutch this early.
I have been searching the net for information, and see that I am not alone. See that there is a TSB which would appear to apply if the car were within 12mo or 12000mi of purchase--otherwise, would require "DCSM authorization."
So my questions are:
1) what does DCSM mean?
2) what are my chances of getting Mazda to fix this, or at least reduce my cost? any advice on tactics?
3) any experience/thoughts about how much savings there is to be had by going with an independent shop?
4) does it make sense to consider an aftermarket clutch?
I want to have this all planned out before the clutch dies--would really appreciate input about this.
#2599 of 2858 Re: clutch shudder [abird]
Jan 13, 2010 (9:19 am)
1. District Customer Service Manager. The Mazda fellow whose job it is to get you off the company's back at the lowest cost.
2. Chances vary. The vehicle age and mileage you're at are not in your favor. Loyalty to the brand and dealer may help. Always pays to at least give it a try. If they turn you down, ask them to explain why the TSB doesn't apply.
3. Estimates are free, often available right over the phone. A reputable independent shop can be 30-50% cheaper and every bit as good. A lot has to do with the cost of the parts, and availability of non-OEM parts.
4. Depends. Typically aftermarkets are higher-performance tuner parts and cost more accordingly - not likely of interest to you. Another factor is how long you intend to keep the vehicle. The repair cost works out to $30 a month amortized over the next five years. Also, what could you buy in its place, even in trade?
Having been in your place (not with my Mazdas), I've gone with the lowest price good shop I could find.
#2600 of 2858 Re: clutch shudder [des5]
Jan 14, 2010 (6:44 am)
Thank you, that is very helpful. Interestingly, the clutch is less symptomatic now that it has gotten warmer.
I think the most likely scenario is that I will end up going with an independent shop. And yes, definitely seems more cost effective to fix rather than trade. I do like the car, and it has treated me pretty well. The only other significant repair was replacing the starter which was done under warranty.
It appears that most of the cost is associated with labor rather than parts. Looks like I can get an OEM clutch for a little under $200, and an Exedy Stage 1 clutch (popular on the mazda6club forum) for a little over $300.
What I don't know is whether the aftermarket clutch is likely to last longer. Any thoughts on that?
#2601 of 2858 Re: clutch shudder [abird]
by Mr_Shiftright HOST
Jan 14, 2010 (9:35 am)
I wouldn't buy an aftermarket clutch unless I spoke with (or internetted-with) someone who installed one. I'd be interested to see about pedal pressure. Some HD clutch packs can be a bear to push on, in traffic all the day long. Also, if the repair shop didn't order the part, then if something goes wrong, the repair shop will NOT warranty the work if it is a parts rather than an installation problem.
Also keep in mind that clutch chatter is not always clutch related---the repair shop should carefully check for oil leaks and unusual wear on other components that work along with the clutch---so, too, motor and transmission mounts.