weird misfire

[dannyboy17]

Car has been acting up lately.
Started three weeks ago with a random misfire, so I didnt pay much attention...1 week ago it woukd just keep misfiring at 2700-2900rpms and now its starting to do it more often, and it different rpm ranges besides that one.

Tried so far:
- diff MAF sensor
- new NGK spark plugs gapped 0.28 - 0.30
- has new coils and wires
- oil level is still perfect
- coolant level is still perfect (headgasket was blown/replaced recently)
- cleaned the gas tank with half a bottle of seafoam

any ideas?
sounds like a fuel/spark problem the way it stutters. It will not do it under WOT though.

Car is running stock boost, splitsecond AFC, FMIC, 3'' exhaust.
Ran perfect for a long time, this just started developing recently.

 

[mazdaspeedp]

thats weird i was gonna say try plugs and wires maybe diffrent plugs? did you do all the coils?

 

[_MSprotegy]

have you tried to check for boost leaks? also check for any frayed wires on your MAF plug. i had a frayed wire and it was running like yours.

 

[dannyboy17]

Im starting to think its an electrical problem somewhere, maybe a fried wire like you mentioned...maybe a bad sensor somewhere. I will take a look at the wires for the MAF this afternoon once I get back from work.

 

[blacktab420]

Maybe the crank sensor shaft....

 

[dannyboy17]

Which sensor is that? You got a pic by any chance where is it located?
Would be hard to test if thats the issue without a replacement one tho

 

[dannyboy17]

Could it be the fuel pump going bad?

 

[_MSprotegy]

do you have an upgraded fuel pump?

 

[dannyboy17]

stock pump.
If its not a sensor or electrical issue, might be the headgasket.

I gave up and set up an appointment with the mechanic tomorrow...Ill keep u guys posted.

 

[dannyboy17]

After a week at the shop and multiple tests, there is still no answer to whats causing this

Its not the headgasket.
Its not the fuel pump (has steady pressure all the time)

HAS to be a sensor somewhere.

It dropped a CEL the other day and it was P0128, so I replaced the coolant temp sensor, but it didnt make a difference.

Its such an annoying problem, and its driving me crazy...dunno what else to check for other than to keep waiting till it gets way worse I guess...that was the mechanic recomendation at least.

 

[Agent42]

I seem to think its still your plugs or maybe the gapping of them, I am not an expert, but just trying to lend a hand my friend.

check out this;

http://www.mazdas247.com/forum/archive/index.php/t-123663017.html

 

[dannyboy17]

I wish it was, however, the mechanic tested the whole ignition (plugs, wires, coils) system and everything tested OK.

 

[Agent42]

Okay, well good luck my friend, be sure to let us know how you make out.

 

[dannyboy17]

This issue is driving me insane.
This weekend I changed the coils again just to be sure that was not the issues, and the misfire is there.
Also replaced the front o2 sensor, to make sure I was getting a correct reading.
Checked and made sure all the electrical connections to sensors were tight.

Same issue is happening, car hesitates horribly between 1500rpms to 3000rpms.
I can leave my floor on the gas to set it steady to 1600rpms and all u hear is the motor hesitate and misfire, feels like its getting flooded with fuel since my mpg has dropped from 300miles per tank, to 250 miles.

I am not sure what else to check for, can an afc go bad? Can the ECU go bad and cause this? Its the only two parts I have not diagnosed, besides an electrical problem somewhere else.

Any other ideas? Its a pain in the ass to disconnect the afc. Anyone has the intructions laying around since I think I threw away mine?

 

[dannyboy17]

The issue is still there
Took out the AFC out last weekened (reset the ECU of course, since the terminals were disconnected the whole time) and took the car for a test drive, and still no luck.

Keeps hessitating randomly anywhere from 1600-2900rpms.
Kind of sucks, I cant even use 5th gear unless Im on the highway lol.

Last night it dropped a P0140 code, which is a faulty o2 sensor (2nd one).
I will go ahead and replace it this weekend with a spare one I have laying around, but I doubt this is the issue.

I noticed a small leak out of the exhaust manifold (between the head and the manifold).
Any chance this could be the cause of this annoying issue?

If its not then I am 100% certain its an electrical malfunction somewhere, which I do not even know where to start to find the problem.

 

[FLAMSP]

have you cleaned the EGR valve?

 

[gorockrx]

How is the idle? Any changes there?
Sounds to me like your spark and fuel are good....its the air mixture that is screwed up...
Of course..that could be caused by a lot of different things.

Start at the intake and work your way to the manifold looking for leaks....

Do you have a boost gauge? How is the boost pattern? Maybe a turbo problem? Maybe
the wastegate not working properly? Since you are running ok at WOT then that is a different Map on the ECU.....just got to figure out why....not easy....and definitely frustrating.

Does it hesitate ONLY with light throttle? any hesitation with WOT? Did the mechanic or
you check the TPS? IF the TPS set screws came loose after the head gasget was fixed,
it could be off...and would cause hesitation and misfire....just an idea.

I have not looked at the manual to see what TPS is on these cars yet....I guess I should
look it up for myself too. I guess we don't have a normal boost sensor either? Mazda has
a 5vdc sensor on most turbo cars..at least the ones I have worked on....

IF I think of any more ideas I will post up....good luck.


Got any video of it hesitating?

I have only owned my MSP for a couple months, but I will have all the systems figured
out before long....I have been into Mazdas for over 15 years and I am pretty familiar with their quirks

 

[christiansMSP]

dude it has to be the coils.. my mom has a voltswagon toareg, and water got into the coils and it was barley running, misfiering like crazy, coils were replaced now everythings fine.. your problem is alot differnt i guess?

 

[StealthWyvern]

dude it has to be the coils.. my mom has a voltswagon toareg, and water got into the coils and it was barley running, misfiering like crazy, coils were replaced now everythings fine.. your problem is alot differnt i guess?

i was thinking coils also but he has already changed them

 

[wesklockmsp]

Im with danny here i have a major problem. My car hasnt misfired but the idle is really low and the car sounds awful running i have no acceleration. the car is shuddering while running and shuddering idling. im pretty sure that its dumping fuel but i replaced MAF and plugs 2,000 miles ago. i dont know what could be causing this. the mods i have:

Injen CAI
Thermal 3" exaust

stock boost, no boost gauge. it was fully checked by a mechanic 2000k miles ago when MAF and plugs replaced