Help with Misfire / Stuttering

[HazardLevel5]

I am having problems with my engine stuttering. A week ago my engine had a couple of misfires during the day, as the day went on the misfires became more frequent until in the evening, as soon as i gave it much gas the engine would stutter and misfire.
I was able to drive to autozone and scanned a cylinder 3 misfire. i brushed off white deposits off the cylinder 3 plug but it didnt help much. the car has newish plugs and wires


I just replaced the coil packs today but it still stutters under heavy load such as low gear at slow speed, but doesnt seem to have trouble with full acceleration through the gears.

Currently no check engine light

Any ideas of what the problem could be?

[drgnzadiel101]

egr or maf maybe? but that wouldnt explain the misfire (huh)

[bgibb68]

it is still missfiring? or is it just stuttering around idle??

[HazardLevel5]

Yes, it is still misfiring under heavy load - not idle though.
If i blip the throttle, i can feel hesitation that wasn't there before my problems started.

And as for the MAF sensor, i keep the filter clean, nothing looks dirty.

[slowtege5]

Could be some clogged injectors

[HazardLevel5]

So you think clogged injectors could cause problems only under heavy load instead of through the full rpm range?

[winston3x]

clogged/dirty "sock" on the fuel pump assy. ? - just another possiblity

[HazardLevel5]

Is there a device that i can test fuel pressure with?
Can a nice OBDII scanner give me detailed information on spark voltage and/or better info than just the cheap ones they let you borrow at autozone?

[winston3x]

here's a how-to about replacing or cleaning the sock

http://www.mazdas247.com/forum/showthread.php?t=107361&highlight=fuel+pump

[VP222]

Is there a device that i can test fuel pressure with?
Can a nice OBDII scanner give me detailed information on spark voltage and/or better info than just the cheap ones they let you borrow at autozone?


You said you have changed coil pack ? Did you change both coil or just one ? I had same problem in My Protege5 but problem went away after I changed both of the coil. My car have 2.0 liter engine in it. Right now I drove around 850 miles without shuttering problem.

[dxaveP5]

what kinda plugs u using?
i had the walmart autolite kind and it was causing misfires and stuttering....so i went with NGK OEM kind and all problems solved in my case. i also cleaned EGR valve.

[bgibb68]

what kinda plugs u using?
i had the walmart autolite kind and it was causing misfires and stuttering....so i went with NGK OEM kind and all problems solved in my case. i also cleaned EGR valve.

+1.....pull your plugs and see what they look like too.....and yeah you can get a fuel pressure gauge that connects to the fuel rail

[silverbullet2]

Change your coil packs.... i was working on my friends pro5 with P0300 code and her CAT was like red hot. i changed her coil packs and it cured it. also, change them soon because if you prolong the problem, you might have to replace your CAT.

also, i recommend using OEM spark plugs.

[HazardLevel5]

OK i changed the plugs with new ones today.
I am using NGK Iridium plugs, but the old ones didn't seem bad; I'll see if i can post some pics of those in a bit.
Still some hesitation on acceleration, not as bad as before though. It just doesnt seem like lightly worn plugs would be the cause of my problems though, any thoughts?

[silverbullet2]

did you change your coil packs? that's might be the problem....

[HazardLevel5]

I just replaced the coil packs today but it still stutters under heavy load such as low gear at slow speed, but doesnt seem to have trouble with full acceleration through the gears.



Yep

And my cat is fouled from a problem a year ago; I've got the 2nd O2 sensor moded so no check engine light from that

[Tifun]

Have you pulled your intake boot off and physically inspected it all around???? Also, is this misfire stutter when under load, or will it do it in idle and or neutral?

[Tifun]

Ignore that last post, I some how missed the two or three posts in regards to those questions. It sounds like an issue we have been having with our car. Our shows cat though. Did you use the fouler trick as your mod for the cat? I am seriously considering it at this point. I went through my records and our cat was replaced not too long ago....

[HazardLevel5]

Yes, I used the non-fouler method for the 2nd O2 sensor

[HazardLevel5]

I replaced the plugs and my misfiring / stuttering disappeared for several weeks...

Two nights ago i noticed some misfires again under heavy load. Today i got the check engine light to come on by driving up a hill in low gear. I scanned at autozone and read a cylinder 3 misfire again...

Plug wires were within tolerance of their resistance rating when i was testing things after the initial problem. Could the problem still be something as simple as a faulty plug wire?

[HazardLevel5]

Could it be a leaking head gasket causing a loss of compression or coolant fouling plugs of something?

[i12drivemyMP5]

Burning extra oil might foul them. Are they gak'd up with carbon bad or just around the threads a little? Could be coil packs or plug wires with or without codes. NGK copper would be the best bet for plugs. I used the NGK iridiums once but they did nothing to improve things but have heard stories about platinums & other trick garbage plugs messing with the motor/ecu. Just bkr5's or zfr5's (long reach) are best. Also as was stated, check your air intake rubber hosery to throttle body for cracks. MAF clean or been cleaned? Check that. EGR shouldn't cause misfires but will screw with idle. If head gasket your oil & antifreeze would be leaking somewhere, smoking of either or both types if bad enough & oil/water would be sharing each other's overflow tank or pan. Check your fluids to be sure they aren't mixed. That takes us to injector cloggage and/or fuel delivery issue with strainer or pump itself. Have seen threads where pump was working but weak & caused misfires IIRC. Maybe bad ground or weak alternator not powering plugs enough, stretching now. Other than that, maybe cam position sensor or crank sensor starting to fail??? Cover all the easy cheaper stuff & eliminate as much as possible. Good luck & let us know what it is when you conquer.

[wildo]

I highly doubt that this is the problem, but since misfiring is a timing issue, and since the timing is electronic- you might take a look at the crank position sensor and the crank pulley (which if stock- has the crank timing gear attached to it). If there was a problem here- you'd likely be running very bad, or not at all- but it only takes a second to look it over...

[slavrenz]

Everyone has so far missed the obvious. He is only getting a misfire in the number 3 cylinder. This rules out things such as a clogged fuel filter, bad coil packs (which, 3 people have told him to replace even tho he said that he did so in his first post (smash)), etc. which would cause a P0300, or random misfire, code.

The only things that can cause a misfire in only one cylinder are:

1. Bad spark plug wire (probably)
2. Bad fuel injector (a stretch, but possible)
3. Intake air leak near the No. 3 cylinder (around the intake manifold, not the intake air boot - doubt it).
4. Poor engine compression in the No. 3 cylinder (doubt it).
5. Electrical malfunction (doubt it)

Replace your spark plug wires and your problem should be fixed. Sometimes they can test good but still perform poorly under heavy load. This is actually almost a textbook case of bad spark plug wires.