Keep having Misfire issue.....

Sport23

Member
Contributor
:
2003.5 MSP
I think NGK has a pre-gapped plug and a universal so it depends on which part number you got.
The purge control solenoid is on top of the intake pipe right next to the throttle body.
 

whatusername

Member
:
02 protege5
gap is .044 and i found the upstream 02 sensor for 22.00 from standard and its not the universal one either (smoke) im interested in knowing what the purge control solenoid looks like cuz i get horrible mpg's and i have new ngk v powers installed. my cel is on but its because im running a header and have not done the plug non fouler trick yet
 

zizaspeed

Member
:
2004 RX8
that's not bad at all. I might just change both my o2 sensors, but we'll see. Now my idle is acting up lol when I start slowing down and down shifting or if I come to a stop and car is in neutral the idle drops to around 400-500 and jumps back up to 750 ish. Like Isaid in my earlier post, I changed the intake to an aftermarket ebay short ram, and have the revised egr valve installed.
 

pcb

The Diagram Dude
:
2002 MP5
i get horrible mpg's and i have new ngk v powers installed. my cel is on but its because im running a header and have not done the plug non fouler trick yet

I'm pretty sure if you are running without the pre-cat, your mileage will suffer. I remember Tweety said that his exhaust smells like rotten eggs at times and there is black carbon deposits in the tailpipe,... and he's got the non-foulers installed. If you've got your cell on (and it's the code you get from deleting your pre-cat) then the car doesn't go into closed loop and it runs extremely rich because it follows a predetermined MAP from the ECU.
I'm pretty sure that the non-fouler trick really only fools the ECU enough to make it go closed loop and not set off the cell,... but it must be still running very rich to leave a smell and carbon in the tailpipe. I'm thinking that can be bad in a lot of different ways. I would think that your car would run dirty all the time, leading perhaps to a clogged cat, fouled plugs, carboned up EGR, fouled O2 sensors, bad gas mileage and even rough running and misfiring.
I actually just bought the non-foulers and I'm going to install them shortly even though I have a healthy functioning pre-cat (make sure you only drill out one of the non-foulers,... there is a how-to for it). I want to use my Ultra-Gauge to see what kind of difference I see in gas mileage, O2 readings, fuel trim readings and to see if my exhaust starts to stink and get dirty.
I'm really thinking that there can be a lot of drawbacks to ditching the pre-cat that all boil down to expense and extra maintenance.
 
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Sport23

Member
Contributor
:
2003.5 MSP
I'm pretty sure if you are running without the pre-cat, your mileage will suffer. I remember Tweety said that his exhaust smells like rotten eggs at times and there is black carbon deposits in the tailpipe,... and he's got the non-foulers installed. If you've got your cell on (and it's the code you get from deleting your pre-cat) then the car doesn't go into closed loop and it runs extremely rich because it follows a predetermined MAP from the ECU.
I'm pretty sure that the non-fouler trick really only fools the ECU enough to make it go closed loop and not set off the cell,... but it must be still running very rich to leave a smell and carbon in the tailpipe. I'm thinking that can be bad in a lot of different ways. I would think that your car would run dirty all the time, leading perhaps to a clogged cat, fouled plugs, carboned up EGR, fouled O2 sensors, bad gas mileage and even rough running and misfiring.
I actually just bought the non-foulers and I'm going to install them shortly even though I have a healthy functioning pre-cat (make sure you only drill out one of the non-foulers,... there is a how-to for it). I want to use my Ultra-Gauge to see what kind of difference I see in gas mileage, O2 readings, fuel trim readings and to see if my exhaust starts to stink and get dirty.
I'm really thinking that there can be a lot of drawbacks to ditching the pre-cat that all boil down to expense and extra maintenance.

I don't think that is correct. If the primary 02 sensor is working then the car should run the same whether or not the pre-cat or second 02 sensor is bad. I'll have to take a look @ my wife's car to verify but I don't know why Mazda would force your car into open loop if the primary 02 sensor is still good.
 

Installshield 2

Gothenburg Superiority
the EGR can cause a p0300...but specific cylinders are usually fuel related, or a very small and concentrated air leak right at that cylinders intake ports...are you positive there are no air leaks right around that cylinder?...positive all injectors checked out and the right colors are in the right places?...to check injector condition, move the problematic cylinder's injector to another cylinder...if the specific misfire follows the injector, there it is...

some guys were getting specific cylinder misfires from the IM gasket...as it was leaking right around just that cylinder...probably unlikely, but something to check if you have the time...

verify, also, that your connections are good at each coil, and each plug wire/boot is contacting the plugs properly...you can try plug or coil location swaps too, to see if the misfire follows...

if you get it to be just a p0300, the door is opened for more culprits...but i'd be surprised if a sticking egr would give a specific cylinder misfire...
 

pcb

The Diagram Dude
:
2002 MP5
I don't think that is correct. If the primary 02 sensor is working then the car should run the same whether or not the pre-cat or second 02 sensor is bad. I'll have to take a look @ my wife's car to verify but I don't know why Mazda would force your car into open loop if the primary 02 sensor is still good.

I was kinda speaking to whatusername specifically (he's running without a pre-cat,...I guess I should have PM'ed him) but I think (this is just my observation) the second O2 is tied in with the closed loop parameters. When I watch my first and second O2 readings with my Ultra-Gauge it really looks like the second O2 sensor has something to do with the fuel trim and is being monitored by the ECU for more than just whether or not the pre-cat is working. Both Installshield and the service manual say the second O2 sensor is only present to monitor the pre-cat but I think otherwise. I think I'll maybe disconnect my second O2 to see what kind of numbers I get but that will set off my CEL which should set the ECU to run open loop (my Ultra-Gauge doesn't ever show closed loop, so I'll just have to watch my O2 and fuel trim numbers). If the second O2 sensor has nothing to do with fuel trim and open/closed loop, then I don't see why the exhaust should stink and get carboned up as well as a drop in gas mileage when people delete their pre-cat and install the non-foulers.
In an effort to bring this back to the OP,... I think the O2 sensors can very well have an impact on MPG and overall drive-ability, although there is 11 different CEL codes that cover the O2 sensors and pre-cat, so you would think that you would get some kind of code if they were bad.
I would like to know if O2 sensors in general "wear out" over time and can go out of spec. but still function enough to not set off a CEL,... maybe kinda like spark plugs becoming weak with age. At around $22 each or so, it doesn't seem like too much money to spend to make sure.
I'm consistently getting between 28 and 32 MPG (US gallons) and only once dropped down to 25 MPG when my air filter was dirty.

Here's what wikipedia has to say about O2 sensor failure.

Sensor failures:
Normally, the lifetime of an unheated sensor is about 30,000 to 50,000 miles (50,000 to 80,000 km). Heated sensor lifetime is typically 100,000 miles (160,000 km). Failure of an unheated sensor is usually caused by the buildup of soot on the ceramic element, which lengthens its response time and may cause total loss of ability to sense oxygen. For heated sensors, normal deposits are burned off during operation and failure occurs due to catalyst depletion. The probe then tends to report lean mixture, the ECU enriches the mixture, the exhaust gets rich with carbon monoxide and hydrocarbons, and the fuel economy worsens.
Leaded gasoline contaminates the oxygen sensors and catalytic converters. Most oxygen sensors are rated for some service life in the presence of leaded gasoline but sensor life will be shortened to as little as 15,000 miles depending on the lead concentration. Lead-damaged sensors typically have their tips discolored light rusty.
Another common cause of premature failure of lambda probes is contamination of fuel with silicones (used in some sealings and greases) or silicates (used as corrosion inhibitors in some antifreezes). In this case, the deposits on the sensor are colored between shiny white and grainy light gray.
Leaks of oil into the engine may cover the probe tip with an oily black deposit, with associated loss of response.
An overly rich mixture causes buildup of black powdery deposit on the probe. This may be caused by failure of the probe itself, or by a problem elsewhere in the fuel rationing system.
Applying an external voltage to the zirconia sensors, e.g. by checking them with some types of ohmmeter, may damage them.
Some sensors have an air inlet to the sensor in the lead, so contamination from the lead caused by water or oil leaks can be sucked into the sensor and cause failure.[4]
Symptoms of a failing oxygen sensor includes:
Sensor Light on dash indicates problem
Increased tailpipe emissions
Increased fuel consumption
Hesitation on acceleration
Stalling
Rough idling
 
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Sport23

Member
Contributor
:
2003.5 MSP
Pcb, 02 sensors can fail lots of ways as you posted. One of the things they will do is get sluggish in their response time. This is monitored in closed loop and will throw a cel when it gets bad enough. I have always wondered how bad it can get before the cel trips though.

Let us know what you find with your testing. The secondary 02 shouldn't cause a change in mixture but who knows what Mazda did with the programming. Also, you can tell when you are in open loop by your STFT going to 0. There is a little bit of a delay on the OBDII but but it will give you a pretty good idea. Finally, Mazda decided to apply LTFT as a correction factor in open loop so you should always have a value for your long term trims.
 

pcb

The Diagram Dude
:
2002 MP5
^^ Yea, I'm positive my car goes into closed loop. The STFT is bouncing around like it's supposed to in closed loop and the O2 readings are also moving, especially the voltage numbers for the first O2 sensor. I really think that our car uses the second O2 readings in the fuel trim for closed loop (that again is just my opinion) because the #1 O2 values seem to follow changes in the #2 values. I'm thinking that may have something to do with why my Ultra-Gauge doesn't show closed loop. (apparently it is the only OBDII gas powered car that UG won't show closed loop for,... that suggests to me that our ECU is doing something weird and completely different from other cars)
Apparently, as an O2 sensor gets old and starts to slow down, it makes the engine run rich and running rich can pop up a 0300- 0304 CEL meaning misfire. So if I was the OP and a new #1 O2 sensor is only $22 then I would replace it, it's easy to change too, and it might even pay for itself after a few tanks of gas in fuel saving alone.
Replacing the #2 O2 sensor may not yield any significant change because you can remove it from the exhaust stream and not notice any drive-ability issues. The #1 O2 sensor on the other hand will definitely cause a drive-ability issue if it craps out and you can't help but to notice it.
I did buy the non-foulers for the second O2 sensor even though I have a healthy functioning pre-cat. I'm just all curious about this whole issue so I spent the $9.80 just to see what will happen if I install them on my car.
 

pcb

The Diagram Dude
:
2002 MP5
Yea,... The first O2 sensor (or upstream,...the one that does all the work) is the one you mentioned. The second O2 sensor (downstream) is further down the pipe almost underneath the car.
It can help a lot to warm up the engine pretty good before you try to break loose the O2 sensor. They are right in the exhaust stream and can seize up really good. The heat can help a lot to break it loose. Be careful of course and wear gloves and long sleeves.
I don't blame you for wanting to track down this problem,... engine miss fire (CEL 0300-0304) is the only code that our car gives that flashes the CEL. It is the worst possible code to throw mostly because just a minute or two of raw gas on the pre-cat can kill it.
 
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zizaspeed

Member
:
2004 RX8
Is there a certain brand I should get over another? It looks like Denso is oem, butI see apw, standard, bosch, and denso.
 

pcb

The Diagram Dude
:
2002 MP5
I personally would buy the APWI,... it's the cheapest and half the price of the OEM supplier (DENSO). It's "hearted" meaning a lot of people are buying it.

I just bought coils and thought I shouldn't cheap out on that particular part so I went for the BECK/ARNLEY (OE supplier). I wasn't impressed when I got them,... they're completely different from each other, the paint, plastic type and color, they were touched up with a paint brush on the metal and I could tell they used a different mould for the two parts even though they had the same part number stamped on the side (different stamp too). I'm sure they will both fit and work (I haven't installed them yet) but they didn't even have enough pride in their parts to put their name on it. I'm pretty sure most companies have their parts made by the same guy at the same factory in China and they all have to meet a certain standard.
So when I order parts from RockAuto, I usually get the cheaper ones with a "heart" beside them unless I hear specific information about certain parts. (like our spark plugs,... our cars apparently run better with NGK and even the cheapest copper electrode ones give the most reliable spark,... they just have to be gapped and replaced more often, but they're as cheap as $1 a piece and the fancy iridium ones can be over $10 a piece and don't even work as well).

Here's a like to my coil quality question: http://www.mazdas247.com/forum/showthread.php?123826094-Ignition-Coil-Quality-Question
 
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zizaspeed

Member
:
2004 RX8
well I got that new o2 sensor, just put it in today along with a megan racing short shifter + corksport bronze bushings. We'll see if this o2 sensor is the solution
 

Dr0

Member
:
03 Black Mica MSP
MAF wont cause a specific cylinder missfire. and secondary 02 does nothing in terms of the running condition of the engine, it just monitors the cats efficiency. I guess other then that i would say possibly check the mechanical side of things?

situations like this suck, but you really need to hold yourself back from throwing parts at it. Although some typical maitence items that are cheap are good to start with, sometimes its best to take a step back and eliminate possibilities 1 by 1.
 

zizaspeed

Member
:
2004 RX8
yeah, I have replaced most of the routine maintenance parts except for MAF. Could the a severe idle drop cause the car to misfire and then cause the CEL?
 

pcb

The Diagram Dude
:
2002 MP5
MAF wont cause a specific cylinder missfire. and secondary 02 does nothing in terms of the running condition of the engine, it just monitors the cats efficiency. I guess other then that i would say possibly check the mechanical side of things?

situations like this suck, but you really need to hold yourself back from throwing parts at it. Although some typical maitence items that are cheap are good to start with, sometimes its best to take a step back and eliminate possibilities 1 by 1.

I'm agreeing with that. If it were me I'd start with another can of seafoam. I'm thinking your #2 injector may still be a little gummed up. As far as MPG goes,... did you replace your air filter. That made a huge difference for me.

Installshield II mentioned this earlier,... Did you try that ???

To check injector condition, move the problematic cylinder's injector to another cylinder...if the specific misfire follows the injector, there it is...


Injector_zps9bec5c8a.jpg


Maybe check again for a vacuum leak,... I used a can of propane with a three foot piece of surgical tubing on the end (unlit). You can aim it very precisely to check for leak.
 
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