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Misfires at highway speeds when decelerating?

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Old 07-16-2009, 04:39 PM
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Exclamation Misfires at highway speeds when decelerating?

for the past 4 months i have noticed that my car sometimes misfires on the highway. recently i noticed it was only when i let off the gas at highway speeds.it now happens every time i let off the gas for more then a couple seconds, but stops soon after i begin to press the gas again. i have replaced the spark plugs, coils, and wires and the promblem still exist. i also removed my cat thinking that might be it but i still get misfires. this all started happening after my car was at mazda for 3 weeks getting the transmission rebuilt. do you think that it may be a clogged/dirty fuel pump or injector from sitting so long? i run shell 93 most of the time and have only used premix about 4 to 5 times. i havent really noticed any loss in power. i have a 2005 mt with 53k miles. thanks for your input. hopefully i gave enough info bc i have limited internet access right now. but i will be online a couple times a day.
Old 07-16-2009, 05:46 PM
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Originally Posted by chancejat
for the past 4 months i have noticed that my car sometimes misfires on the highway. recently i noticed it was only when i let off the gas at highway speeds.it now happens every time i let off the gas for more then a couple seconds, but stops soon after i begin to press the gas again. i have replaced the spark plugs, coils, and wires and the promblem still exist. i also removed my cat thinking that might be it but i still get misfires. this all started happening after my car was at mazda for 3 weeks getting the transmission rebuilt. do you think that it may be a clogged/dirty fuel pump or injector from sitting so long? i run shell 93 most of the time and have only used premix about 4 to 5 times. i havent really noticed any loss in power. i have a 2005 mt with 53k miles. thanks for your input. hopefully i gave enough info bc i have limited internet access right now. but i will be online a couple times a day.
I'm not sure why you say it is misfiring? When you take your foot off the accelerator and you are in gear decelerating, gas is shut off to the engine.
Old 07-16-2009, 05:48 PM
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i get a flashing cel when decelerating and after a couple times it stays on (but still flashes during misfire). check the codes and have a cylinder(rotor) 1 misfire and multiple cylinder(rotor) misfires.
so fuel cuts off completely? maybe i have a bad sensor or something. do you know what sensor senses misfires?

Last edited by chancejat; 07-16-2009 at 05:52 PM.
Old 07-16-2009, 06:01 PM
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IDK go look at your fuel pump and clean your MAF sensor.
Old 07-16-2009, 06:04 PM
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so no cel when accelerating but it suddendly comes on when decelerating ?

Any other symptoms other than the cel ?
Old 07-16-2009, 06:09 PM
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no...i havent noticed any power loss.....i can still bark 3rd gear......around the city i get no misfires at all only when im on the highway for more then like a min......its really strange...
Old 07-16-2009, 06:18 PM
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how do i reset the eshaft profile?
Old 07-16-2009, 06:25 PM
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thanks charles......ill update in a day or two.....
Old 07-16-2009, 07:03 PM
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Originally Posted by Charles R. Hill
As shazy mentioned, clean the MAF (just for the Hell of it) and I would suggest resetting the e-shaft profile. Maybe clean the e-shaft sensor, too. It is located on the front of the engine under the A/C compressor.
+1 on these it's a good place to start. I did find a "TSB" that sounded like your problem till you said you had a CEL. Look a this....

DESCRIPTION
Some vehicles may experience the following symptoms.
- On manual transmission vehicles, when decelerating in 3rd gear with engine speed less than 3,000 RPM at
approximately 30 MPH (50km/h), then quickly depressing the accelerator pedal again, a hesitation may
occur. This symptom can only be observed in this engine speed and vehicle speed range.
- On automatic transmission vehicles, when at a stop in D range, excessive engine/body vibration may occur.
This body vibration does not occur in P or N range.



http://www.finishlineperformance.com...01-09-2062.pdf
Old 07-16-2009, 07:20 PM
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you can bark third? i cant do that... now im more worried about my car. i wonder if i have lost power. can everyone bark third?
Old 07-16-2009, 07:59 PM
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Depends on your driving skills. The 8 has enough power to..
Old 07-16-2009, 08:21 PM
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Originally Posted by zoomman
you can bark third? i cant do that... now im more worried about my car. i wonder if i have lost power. can everyone bark third?
I can't even do that with a turbo producing 2x the torque of a stock 8
Old 07-16-2009, 08:26 PM
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friend did that once he kinda flatshifted it by accident (my clutch engagement was diffrent compared to what he was used to) 3rd gear barked the tires
Old 07-16-2009, 08:32 PM
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he pressed the accelerator before letting off on the clutch ? So that's that how you do it !
Old 07-17-2009, 10:38 AM
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its more of a chirp....
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