Jerky at low revs

Hi guys.

I am driving a Mazda 6 Automatic 2.0 2005...

I have recently replaced

- Spark plugs (mazda platinum)
- Air filter (Mazda)
- Drained and filled Dexron III (Purchased ATX Fluid from Mazda) ATX fluid
- Replaced ATX filter (mazda)


The problem, that I need your help with :

When I release the brake pedal (so that the car rolls forward on its own) occaisonally, it will start to jerk between 930-980 revs and this feels like it is misfiring..

Sometimes this never happens. It almost always happens when the revs fluctuate (low rev rolling), e.g. when the A/C compressor comes on or when I do a full lock steering, the jerkiness can be quite strong...

When I then place some acceleration this just goes away and it acts normal (sometimes there are delays in accleration or it accelerates too willingly...)


Some ideas I was thinking:

- Clogged Fuel Injectors
- Spark plug wires need changing
-Ignition timing needs adjusting
- Engine timing...
- Fuel Filter (located inside fuel tank) needs changing...

Can someone please help identify possible problems, give me your opinions...Thanks in advance.

Regards

M6Newb...

Here you go-
http://forum.mazda6tech.com/about3015.html

This should hopefully fix the problem. My car does the same thing...

thanks for your input Mazda6irl.

I was looking at that problem, and I dont think it is shift shock related, since the Jerky movement occurs when the car is rolling forward under its own steam, I.E. in 1st gear, when I let go of the brake pedal, the automatic just moves forward and appears to be misfiring...

Anyone else, please have a go, dont be shy...

This is just my $.02.

1. Engine/Ignition timing is going to be computer controlled, the only way for you timing to be off is going to be if the motor was being disassebled to where the cams may have been moved/the cams slipped on the chain, or the cam/crank position sensors / Throttle Position sensor(s) are bad. Could also be computer, but computers don't typically just go bad.

2. Fuel filter typically causes hesitation during acceleration when there is more demand for fuel and the clogged filter doesn't allow for enough pressure.

3. Car seems a little new for needing plug wires and, you should consistantly feel less acceleration/power available.

4. Same thing with clogged injectors. (You could try running a good fuel injector/fuel system cleaner to attempt to unclog the injectors or pay the $100 for a fuel system flush)

Considering this happened after you changed the trans oil, I would make sure you got enough or not too much trans fluid, though I'd hope the dealer was able to give you the correct amount of trans fluid. Could be a problem concerning the clutch pack(S) in the trans?

Hope I helped.

Yeah, my car will jerk when I let off the pedal and it is sort of idling. I get one kind of big jerk. I will be taken mine in soon..

Just to add:

The jerky reaction can also be initiated (while rolling forward under its own idling power - automatic) by Using the steering wheel at full or full lock turn. Then it does a noticable jerk, until I level off straight and then it will do less of the noticable jerking...The A/C compressor also causes a jerk at idling rolling forward...

Under acceleration or faster speed, there isnt any problems with the above...


I have also changed one tyre recently, and I now hear a whirring sound (orginating from the tyre changed) as I increase speed, the whirring increases...

I purchased the car used and it had no warranty...what a mistake I made ...

my '06 6 kinda does the same thing: when i slam on the accelerator it seems to hesitate then, after a second or two, it kicks in. and sometimes when i'm just idle the RPM's will all of a sudden dip way down then shoot right back up....WTF?!?!??! i think it has something to do with the computer. i heard from here that there is an update that you can get downloaded to your computer from the dealership....i'm gonn try it...as for your no warranty situation...not a good move buddy. BUT, you can still buy a warranty from an outside company! there almost as comprehensive as the manufacturer's...just google it.....good luck...


Thumbnail Image

I just had a flash though it is something simple. When you installed the spark plugs (if you did it yourself), did you propperly gap them?

Good thawt JB!!! Definetly a possibility!!!


Thumbnail Image

TY zen. I remember one of my former co-workers had an eclipse and ran into a problem with misfiring when he installed plugs without gapping them. They were only of by like 2 thousandths and he was having this problem. He thought it was his coil, but the problem came back like a week after he installed the new coil. So he checked the plugs, regapped them, and BINGO, no misfire.

thanks for your advice guys..

I didnt install the spark plugs myself...

And I have no idea what gapping is... can someone explain what regapping a spark plug is or involves? I can take it back to the private service garage and I can get them to do it...

I have also pinpointed the problem to occur mainly with the A/C activated...without the A/C on the car behaves better....hmmmm

Well the a/c is ALWAYS going to have an effect on vehicle performance, especially a low-torque 4 cyl at low engine speed. I know you're not an idiot but are you absolutely SURE you're not just being paranoid and the car always did it with the a/c on and you didn't pay attention? It's natural to always be more observant after getting your car worked on. To be honest, it doesn't really sound like something may be wrong... When you turn your steering wheel to full lock, you are putting serious strain on the power steering pump, so it tries to pump more to assist the steering, and since the pump is powered by the motor, this drains the motor of more power, of which there is very little at idle, which would possibly cause jerking. Same for the a/c at idle just rolling forward, the a/c is a drain on the engine as well, and there isn't a lot of power at idle to begin with. If your plugs were mis-gapped, the problem should be more consistant, and during acceleration. You can have it checked if you like, but I don't think there's really something wrong with the car. Seek as many opinions as you can though, as I am human and can be wrong.

As for the tire, there are little rubber knobs or needles all over the tire, as well as the deep, new tread. New tires will make a humming noise for a little while until those needles are gone and the tread is a little worn. Should be nothing to worry about, just don't drive too hard on brand new tires as they can be a little slippery.

Here is an explanation of gapping(don't mind the horrible diagram):

Gapping involves changing the space between the center electrode (the piece of metal surrounded by porcelain in the center of the threaded part of the plug) and the ground (small curved piece of metal that goes from the threads to the center of the electrode) using a spark plug gapper, of which there are several variants, which basically adjusts the strength of the spark and the time it takes for the spark to jump from electrode to ground, as well as the energy required to jump the gap. The manufacturer offers the specifications in your owners manual and usually on a sticker under the hood. Refer to my ghastly rendering below for the basic locations.

Hope this helped.

___ This would be the GROUND
/ This would be the GAP (measured in thousandths of an inch i.e .020")
/ _|_ This would be the ELECTRODE
|__| |__|
|_______| Threads
|_______| Threads
|_______| More threads
/________\
|__|____|_ | Nut shaped area for the socket
| |
\ /
\ /
\ /
| |
| | Connector
\_/

aww man! the diagram looked a lot better in the reply window! It took out all the spaces I used to line everything up! I hope you can still get the picture, if not, I'll actually put in a picture of a spark plug and show you. You could also go to auto zone, napa, kragen or pep boys and ask them to show you.

Thanks alot for your effort and time JBix. You have been really helpful.

You're very welcome, hope I helped.