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Drew, Super Mazda Tech.
Category: Mazda
Satisfied Customers: 2518
Experience:  19 yrs. experience. Mazda Senior Certified Tech, with Ford, Linc. & Merc. experience. ASE L1 Advanced Certified Master Tech.
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2003 Mazda 6: V6..My car starts and revs..throttle..injectors

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"2003 Mazda 6 V6 3.0" My car starts and revs quite normal, but when it reaches between 35mph to 40mph and I release the throttle and press again, the engine starts to give a sudden vibration more like slamming real hard and if i should come to a sudden stop and tries to move off with any speed the car feels like its struggling, to re-leaf that i have to wait a while then i can press again. any ideas?
Ive change plugs, coils. only injectors left.

Welcome to Just Answer. My name is XXXXX XXXXX I will be glad to assist you.


Is the check engine light on?


Are there any fault codes stored?


Can you duplicate this concern during a power brake test?


Let me know.



Customer: replied 6 years ago.
yes the CEL is on,<br /><br />codes stored are: <br />P0455<br />P0421<br />P2404<br />P0442<br />P0113<br />U0073.<br /><br />what do you power break test?

Have you cleared the codes and test drove to see which ones come back?


You have 3 different areas of faults according to your codes.


Inspect the IAT/MAF (intake air temp sensor/mass air flow sensor) connector for poor connection or damage. This is related to code P0113


P0455, P2404, P0442 are all related to an EVAP emissions fault.


P0421 is related to a faulty CAT CONV.


U0073 is a communication fault between modules and is usually caused by a low battery.


None of these codes are for a misfire. Clear the codes and test drive.


Let me know your results.


Customer: replied 6 years ago.
yes, i cleared it twice already,

and i didnt get back v0073,

but all the rest.

Its really getting to me now! when im above 48mph i have no problem.

the very first time i scan i got misfire in cylinder 1, but i change all what i said earlier, but still having the same probp; and i didnt get back the misfire code.....

so what you think?

Have you checked or replace the fuel filter recently?


Pinch off the purge solenoid hose that attaches to the engine. Test drive for change.




Do you have a scan tool that reads live data or just a code reader?


Disconnect the battery and touch the cable ends together for 30 seconds. Clean as needed and reconnect. This will reset the module.


Test drive and let me know which codes come back.

Customer: replied 6 years ago.
fuel filter; never change/check.

cant see the image that clear but i'm going to look in the hood now.

no i dont own a scan tool, but it does read live data.

do you have skype?

Ignore the fuel filter, I was thinking about a different car.


You scan tool reply is ??? You do NOT own a scan tool, but it does read live data?? What reads live data and hoe did you get these fault code read??


We can only communicate through the JA site. Sorry.


Also try and clean the MAF sensor and test drive. Try and test drive with the MAF connector disconnect. Note any change.


Here is another diag.


I will check back for your reply in the morning.



Customer: replied 6 years ago.
I'll try them in the morning.

The scan tool read codes and also read live data... example I can see the time (how long) the injector opens (spray) for etc...

i see this diagram now.
Customer: replied 6 years ago.
i tried it (removing) the purge solenoid hose, when i do so; the engine struggles very hard almost sound like it about to stalled.

At what point should the valve be open, it seems like a normally close, as the car starts or at different intervals?

Sorry for the delay.


Happy New Year.


The purge valve is supposed to be normally closed. It opened during cruise speeds.


I just wanted you to pinch off the hose for the purge solenoid where it connects to the engine. If you removed it, there should have been a vacuum leak, unless you plugged the leak.


With your scan tool, let me know what the short and long fuel trims are, with the engine running, warm at idle.


Did you perform the other test also and what were your results with the MAF??

Customer: replied 6 years ago.
Happy new year to you as well.

(Purge valve) OK

I did get a vacuum leak.

To be honest, I've gotten some improvement since I clean the MAF.(there is a adjusting screw on the purge valve also; I did a anticlockwise turn on it too) I can stil feel the stuttering in the engine but I've not gotten the slamming so far.... So it seem we are heading the right direction.

Were you able to get the fuel trims for me??


Does the stuttering feel like a misfire?


Do you only get the stuttering on acceleration??


Does the engine idle smooth??


Can you duplicate the stuttering by doing a power brake test??

Customer: replied 6 years ago.
No I didn't, The scan tool is not mine, as soon as I can do it ill let you know.

Yeah, Thats what it feels like.....

let me explain more...
moving from "0" and i want a quick take off..... it starts off good then it feels like i loose power (RPM drop) for a split second, then i regain power, this happens 3-4 times before the power is maintained.

Yes, only at acceleration.

It does idle smoothly, at times if i give it a sudden rev-up it has a misfiring feel at the beginning.

"Power break test" I don't understand.
That is good information.

Clear all the fault codes. Disconnect the battery. Touch the cable ends together for 30 sec. This will reset the module.

Test drive the van until the check engine light comes back on or starts flashing.

Let me know the fault code number.

It sounds like you may have a faulty ignition coil causing a slight misfire on acceleration.

A "power brake test" is, at a stop, shifter in drive, foot on the brake, slowly apply gas and notice if the misfire is felt.
Customer: replied 6 years ago.
how do i accept?

I haven't given you an answer to accept yet.


Have you resolved your concern??


Here is a answer that you can accept.


If you still need help, just hit the reply button and I will be glad to assist.




Drew and 5 other Mazda Specialists are ready to help you
Customer: replied 6 years ago.
There was great improvement in the "Car" I don't feel that vibration/misfire anymore; I change all the coils. I didn't get a chance to scan,I know I need CAT converter change therefore when I do can I still contact you?

Yes you can contact me any time. Simply reply to the question and I will be here to help.