P0302 (p0172)

S

Sailingsenses

Member
:
Mazda, Protege5, Stock, 2002
Long and short of it:
301,000 miles
Stock
2002 p5


-- Car stalled, smelled of gas, smoked up white.
-- CEL came on.
-- Codes P0302 (misfire cyl #2) and P0172 (System Too Rich (Bank 1))

-- Found super cracked intake hose.
-- Replaced hose, air filter, and cleaned MAF.
-- Never unplugged battery...
-- Both codes gone.
-- Slight hesitation and low power at around 4,000rpm.
-- No CEL or codes for 100+ miles.
-- Something was off during hwy driving...kind of a limp low power thing at higher speed. Misfiring I suppose...but still no CEL.

<> Fast forward less than a couple of weeks:
-- Car hesitates during hwy driving big time.
-- CEL came back on.
-- Kept my foot on gas and got us home...not very far.
-- Only P0302 came back.

-- Replaced:
- Ignition coils/pack (2)
- PCV + grommet (which was fried and stuck)
- Spark plugs (4) but did not gap (okay?). They looked awful.
- Wires (2)

Basically did a full tune-up but no oil change (yet).

-- I unplugged the battery to do the tune up, so the CEL was gone.
-- Drove in circles in the neighborhood to see if I could reset the idle, which was very limp and wobbly...and hesitating at stops or when I let off the gas at a slow turn. Idle was complete s***.
-- Car start is good. Car is quiet.
-- The car stalled twice at very low speed, when I was not accelerating.
-- I looked around a lot, and was told that the computer probably needed to reset and figure out the idle again.
-- So I drove and drove and drove, and let in run idle with parking brake for many minutes.
-- Seemed as though the idle was improving.
-- Went on highway for some time.
-- After 50 miles, weirdness again (misfire?), loss of power, would not accelerate, hesitation.
-- CEL back on.
-- Stalled at at light when I got off hwy.
-- Only P0302 this time, so I stopped driving it. The other code could possibly return, too.

WHAT COULD THIS BE?
<> EGR? -- Wouldn't that throw its own P0400 series code?
<> Injectors? -- Seafoam treatment?
<> Vacuum leaks? -- No clue how to handle this at all.
<> Fuel pump? -- I sure hope not. What a drag that would be. Again, wouldn't this trigger its own codes?

<> As of September 2012, this has been done:
-- New catalytic converter (OE).
-- New Upstream and Downstream oxygen sensors.

<> As of June 2013:
-- Compression Test - OKAY (factory specs)
-- Timing Belt, all seals, tensioner, idler, adjust ignition Timing
-- New transmission.

PLEASE help. It seems like this is a common problem, and there are so many posts and yet no definitive answers. Of course misfires happen for a variety of reasons, but I can't see why there aren't any solid postings on this. Start to finish. Problem to success stories...

Also, if the CEL is not blinking, can I drive it for a few miles? I know it would eventually fry the catalytic converter, but if I drove it to the shop up the road, that would not be awful, right?

Thanks.
 
Last edited:
Sailingsenses said:
WHAT COULD THIS BE?

<> Injectors? -- Seafoam treatment?
Click to expand...

That's my guess... Sticking or fouled injector.

Sea foam is cheap and easy... You'll want it in your gas so it runs through your injectors.

Try to rub your code with a reader so you don't have the crappy idle come back and to bring it out of limp mode... Then you can keep an eye on the cell to see if it comes back during the cleaning process.

A flashing cell is really bad news and an engine misfire is the only code that flashes the cell for our car...

It is only one cylinder misfiring but it's still bad news... It's possible that the injector is sticking closed meaning no gas in the cylinder causing the misfire, which would be safe for your pre-cat but you'd be guessing...
An injector sticking closed could perhaps cause a lean condition too.
 
Last edited:
pcb said:
That's my guess... Sticking or fouled injector.

Sea foam is cheap and easy... You'll want it in your gas so it runs through your injectors.

Try to rub your code with a reader so you don't have the crappy idle come back and to bring it out of limp mode... Then you can keep an eye on the cell to see if it comes back during the cleaning process.
Click to expand...

I have this cheap OBDII reader and it has an "erase" option...are you saying, just erase it using the reader itself, add the seafoam, and drive around until the CEL either does or does not return? Can you clarify on that, please? I'm not mechanically inclined, just have done some easy stuff based on youtube and this forum.

Also, would it be overkill to use Seafoam fuel additive (only) AND the spray-in intake cleaner version? I've never used an additive or cleaner of any kind, so will doing both be a waste here?
(http://seafoamsales.com/sea-foam-spray)

Last thing: The CEL blinked very very briefly...then just stayed on. In terms of being able to drive it, is that a good thing? I'm not sure if you meant that a perpetually blinking light is a real thing...? In other words, mine is not anymore...so, is it okay to keep driving it around while I experiment with cleaning the injectors?

THANK YOU!
 
Sailingsenses said:
I have this cheap OBDII reader and it has an "erase" option...are you saying, just erase it using the reader itself, add the seafoam, and drive around until the CEL either does or does not return?
Click to expand...

Yes... The cell will come back on and flash the instant you misfire... If it doesn't come on then you're good to clean safely.


Sailingsenses said:
Also, would it be overkill to use Seafoam fuel additive (only) AND the spray-in intake cleaner version? I've never used an additive or cleaner of any kind, so will doing both be a waste here?
Click to expand...

The spray kind is mostly for cars that are hard to work on.

Regular sea foam goes in either the gas, the oil, or the intake. (brake booster line for our car)

If you have a sticky injector, you want it in your gas to run it through the injectors (especially number 2 cylinder)

Sailingsenses said:
Last thing: The CEL blinked very very briefly...then just stayed on. In terms of being able to drive it, is that a good thing? I'm not sure if you meant that a perpetually blinking light is a real thing...? In other words, mine is not anymore...so, is it okay to keep driving it around while I experiment with cleaning the injectors?

THANK YOU!
Click to expand...

The instant your car misfires, the ECU says "holy crap" and does everything it can to stop it (limp mode) ... Then it leaves the CEL on to let you know it's pissed off.


I am a firm believer in seafoam ( no I don't work for them)... If any car is being fussy it may just need a good cleaning... I think you should always clean it before you throw good money at it.

Clean it... If that doesn't work then start throwing money at it. (like that Canadian EGR for instance... which by the way can be cleaned up with seafoam...)
 
Last edited:
I would remove the fuel injector and swap it with the one next to it, if the misfire follows the cylinder you'll know where the problem was. An injector balance test accomplishes the same thing without disassembly, but you likely won't be able to acquire the necessary tools for that.

The EGR typically causes a PO300 code, since it affects all cylinders, not just one. But it can cause others, so it should be considered.

I would also do a power balance test to see if #2 cylinder is consistently misfiring. With the engine idling, unplug each fuel injector one at a time. The engine will slow down and sputter when you unplug a contributing cylinder. A cylinder that is misfiring will make no difference with the injector unplugged. If the engine runs rough but you cannot pin point a specific cylinder, look into vacuum leaks or the EGR.
 
MrGiggles said:
I would remove the fuel injector and swap it with the one next to it, if the misfire follows the cylinder you'll know where the problem was. An injector balance test accomplishes the same thing without disassembly, but you likely won't be able to acquire the necessary tools for that.

The EGR typically causes a PO300 code, since it affects all cylinders, not just one. But it can cause others, so it should be considered.

I would also do a power balance test to see if #2 cylinder is consistently misfiring. With the engine idling, unplug each fuel injector one at a time. The engine will slow down and sputter when you unplug a contributing cylinder. A cylinder that is misfiring will make no difference with the injector unplugged. If the engine runs rough but you cannot pin point a specific cylinder, look into vacuum leaks or the EGR.
Click to expand...

Either way .. You wanna clean the patient and yourself before doing surgery. .

He has a chance of fixing this with a good cleaning... Even carbon buildup on top of the cylinder can cause a misfire... Sea foam can remove it...

Sailingsenses said:
...I'm not mechanically inclined, just have done some easy stuff based on youtube and this forum.
Click to expand...

We should start him off easy...
 
Last edited:
Hi all,
Thank you very much for all the contributions above. I did the seafoam only in the gas tank, and drove around for about 25 miles, so far so good. No hesitation, no stalling, no weirdness or idle wobbliness on the road. I wound up putting ten gallons of 93 Vpower Shell gas in it for kicks, as it's loaded with cleaner.

How long before I can use another can of seafoam? Should I? I figured if it's that dirty...try another can, but when?

I've driven almost 50 miles, and still no check engine light or codes are present. I'm afraid to feel hopeful about it...but, damn, the car feels great. It certainly did not feel this way a few days ago, or when I first replaced the intake hose about 200 miles ago. None of those symptoms are present right now.

I have a new EGR sitting in a box and I am going to replace it someday soon. At 301k...why not, right? Bound to give me crap...

I am scheduled for an oil change tomorrow, and I'll have them check the fuel injectors. It is a chain type shop, so I don't expect they're going to spend a whole lot of time or energy cleaning out my fuel system...in a real way. I'm sure it needs some major cleaning.

I found these two really great articles...not Mazda specific, but still pertinent: http://www.clubwrx.net/forums/gener...you-have-misfire-code-please-read.html#/enter

http://repairpal.com/is-it-really-worth-performing-a-fuel-system-cleaning-438

You're all awesome for helping out. Truly.

I will keep you posted with further developments.
 
Last edited:
PCB said: "If that doesn't work then start throwing money at it. (like that Canadian EGR for instance... which by the way can be cleaned up with seafoam...)"

Oh...what's up with the Canadian EGR? Is that the one to get or the one to avoid like the plague? Mine is Mazda OE...
Not sure where it was made, presumably Japan (I'll check the box).

My fear is not being able to get those bolts out--even if I manage to get my hand in there. Corrosion seems likely...
 
Last edited:
The Canadian EGR has the coolant lines hooked up to it.. It is way better than the original...
it was first introduced to the Canadian market only (hence the name)

It is more of a pain to hook up but they don't cause problems.

I have the original EGR on my car (225,000 km)... It has yet to give me a problem... In leaving it alone till it's an issue.
(I'm convinced it's because of the seafoam... car is super clean... internally anyway)


 
Last edited:
Sailingsenses said:
How long before I can use another can of seafoam? Should I? I figured if it's that dirty...try another can, but when?


I am scheduled for an oil change tomorrow, and I'll have them check the fuel injectors. It is a chain type shop, so I don't expect they're going to spend a whole lot of time or energy cleaning out my fuel system...in a real way. I'm sure it needs some major cleaning.
Click to expand...

Did you put a full can in the gas ?? How much gas was in the tank??

I don't really know how much is too much but if it were me I'd keep up with the seafoam.

I add a shot with every fill up to keep things clean.

As soon as my idle gets a little stumbly I put some up the brake booster.

My car is so clean now that I add sea foam to my new oil and leave it in.

Last time I had my tailpipe sniffed he thought his machine was broken... I had less pollution than when the car was new...

I would put half a can or more in the oil now before your oil change... Drive the recommended distance then get it changed

I would wait for the injector test.
 
Last edited:
I did put a full can of Seafoam in the tank, when it was just over 1/3 full.

Drove car 70+ miles and no CEL or misfire; after seamfoaming it, I drove and drove and drove some more, and added the Shell Vpower higher octane gas to almost full. The next day, I had the oil changed, and wound up having a shop check the fuel injectors and NONE of them were clogged. Regardless, I wound up doing a *chemical* fuel system cleaning. After all, the car is deserving of this basic maintenance, which I've only done once before many miles ago.

I drove away from the shop and the hesitation and lack of power coming out of a full stop was just awful--substantially worse than before I had the fuel lines cleaned just moments before. Every red light and stop sign, same symptom. It wasn't stalling, and still no misfire/CEL.

I drove right back to the shop and the mechanic double-checked my at-home tune-up job (which included a PCV + Grommet), including the spark plug gaps (which were fine). Everything was golden there, but the spark plugs didn't look as fresh as I would've expected (white buildup on them after just three days). Running rich? No codes for that, but...what should I look out for?

While looking at it closely with him, I realized the NEW PCV valve was bulging up higher than I had originally placed it, which was presumably ALL the way in (kind of hard to mess that up). Somehow, the NEW Grommet was not keeping its seal, and was just coming up and out. It may have been a very bad quality or just the wrong part...and if the latter, I sure as heck didn't notice. (Unless there is another cause for the darn thing to come up like that? I will keep an eye on it.)

IF the pre-tuneup disintegrated PCV grommet that was the root cause of all this, then this would be very much consistent with the last time I had a misfire and everything fell apart on me. When I say "disintegrated PCV grommet", the thing was in pieces when I pulled it out and I had to fish out tiny bits of it that fell off. There is NO chance that thing was holding a seal properly, and it required brute force to remove it all the way.

Check this out:

http://agcoauto.com/content/news/p2_articleid/197

After all, a bad PCV (whole system therein) can cause all kinds of other, very costly problems. I would know, from a few years back...when I had a misfire and fried my catalytic converter because I was too stupid and drove around with a CEL for a long time (embarrassed by that now).

Anyway, MANY people believe all of those problems began with this simple and inexpensive part. Mind you, the valve itself can be just fine but that crappy seal can fail and Mazdas are notorious for problems in this department. Read more here:
http://www.motorweek.org/features/goss_garage/clearing_up_pcv_valve_problems

Anyway, the NEW grommet all but fell apart when we pulled it all the way out; it even fell in, and we had to go fishing. Either the new grommet was total crap quality or I actually didn't push it through properly (which seems odd given it either goes in or it does not).

We bought a very good brand grommet and everything has been going really well. We didn't reset the computer, so the 80+ miles I've driven since the full tune-up are legitimate (continuous) engine cycles...and still no CEL/misfire, and the hesitation stopped.

I don't know ALL of this began from the practically disintegrated grommet (original prior to tune-up), but I'm feeling like it did. Call it a hunch! The NEW grommet failed, too...so that is suspect in the awful hesitation I had after the fuel cleaning (the more it bulged out and seal failed, the worse things got).

Bottom line is:
-- Replace the freakin' PCV + grommet fairly often
-- Check the two hoses going into the valve
-- Make sure the new parts are the right fit
-- and DO NOT get cheap brands if you can help it.
-- Don't ignore this important step when addressing stalling, hesitation, rough idle, running rich, or what you think may be EGR problems and/or fuel line grime. It's the gift that keeps on giving...and fkkks up your car VERY easily. It should not be underestimated or forgotten as part of routine maintenance.

I still plan to replace the EGR, but that will be in my spare time, maybe after I drive it another 100-150 miles...depending on when and if the P0302 and/or P0172 problem returns. I'm hoping for the best here...

I will keep an eye on that valve MUCH more consistently, that's for sure. I will also post any updates to the CEL and misfires, should they return. I'm almost afraid to think it's "over"...but I can hope, right?

Thanks all,
Sailingsenses
 
Last edited:
Sailingsenses said:
I drove away from the shop and the hesitation and lack of power coming out of a full stop was just awful--substantially worse than before I had the fuel lines cleaned just moments before. Every red light and stop sign, same symptom. It wasn't stalling, and still no misfire/CEL.
Click to expand...

Keep in mind that if the battery was disconnected (which I assume it was) the car will run like crap till it learns how to idle again.

My car gets nasty shakes while relearning. I know it's going to happen so I'm used to it.

You my have had two things going on...
 
Sailingsenses said:
I did put a full can of Seafoam in the tank, when it was just over 1/3 full.

Drove car 70+ miles and no CEL or misfire; after seamfoaming it, I drove and drove and drove some more, and added the Shell Vpower higher octane gas to almost full. The next day, I had the oil changed, and wound up having a shop check the fuel injectors and NONE of them were clogged. Regardless, I wound up doing a *chemical* fuel system cleaning. After all, the car is deserving of this basic maintenance, which I've only done once before many miles ago.

I drove away from the shop and the hesitation and lack of power coming out of a full stop was just awful--substantially worse than before I had the fuel lines cleaned just moments before. Every red light and stop sign, same symptom. It wasn't stalling, and still no misfire/CEL.

I drove right back to the shop and the mechanic double-checked my at-home tune-up job (which included a PCV + Grommet), including the spark plug gaps (which were fine). Everything was golden there, but the spark plugs didn't look as fresh as I would've expected (white buildup on them after just three days). Running rich? No codes for that, but...what should I look out for?

While looking at it closely with him, I realized the NEW PCV valve was bulging up higher than I had originally placed it, which was presumably ALL the way in (kind of hard to mess that up). Somehow, the NEW Grommet was not keeping its seal, and was just coming up and out. It may have been a very bad quality or just the wrong part...and if the latter, I sure as heck didn't notice. (Unless there is another cause for the darn thing to come up like that? I will keep an eye on it.)

IF the pre-tuneup disintegrated PCV grommet that was the root cause of all this, then this would be very much consistent with the last time I had a misfire and everything fell apart on me. When I say "disintegrated PCV grommet", the thing was in pieces when I pulled it out and I had to fish out tiny bits of it that fell off. There is NO chance that thing was holding a seal properly, and it required brute force to remove it all the way.

Check this out:

http://agcoauto.com/content/news/p2_articleid/197

After all, a bad PCV (whole system therein) can cause all kinds of other, very costly problems. I would know, from a few years back...when I had a misfire and fried my catalytic converter because I was too stupid and drove around with a CEL for a long time (embarrassed by that now).

Anyway, MANY people believe all of those problems began with this simple and inexpensive part. Mind you, the valve itself can be just fine but that crappy seal can fail and Mazdas are notorious for problems in this department. Read more here:
http://www.motorweek.org/features/goss_garage/clearing_up_pcv_valve_problems

Anyway, the NEW grommet all but fell apart when we pulled it all the way out; it even fell in, and we had to go fishing. Either the new grommet was total crap quality or I actually didn't push it through properly (which seems odd given it either goes in or it does not).

We bought a very good brand grommet and everything has been going really well. We didn't reset the computer, so the 80+ miles I've driven since the full tune-up are legitimate (continuous) engine cycles...and still no CEL/misfire, and the hesitation stopped.

I don't know ALL of this began from the practically disintegrated grommet (original prior to tune-up), but I'm feeling like it did. Call it a hunch! The NEW grommet failed, too...so that is suspect in the awful hesitation I had after the fuel cleaning (the more it bulged out and seal failed, the worse things got).

Bottom line is:
-- Replace the freakin' PCV + grommet fairly often
-- Check the two hoses going into the valve
-- Make sure the new parts are the right fit
-- and DO NOT get cheap brands if you can help it.
-- Don't ignore this important step when addressing stalling, hesitation, rough idle, running rich, or what you think may be EGR problems and/or fuel line grime. It's the gift that keeps on giving...and fkkks up your car VERY easily. It should not be underestimated or forgotten as part of routine maintenance.

I still plan to replace the EGR, but that will be in my spare time, maybe after I drive it another 100-150 miles...depending on when and if the P0302 and/or P0172 problem returns. I'm hoping for the best here...

I will keep an eye on that valve MUCH more consistently, that's for sure. I will also post any updates to the CEL and misfires, should they return. I'm almost afraid to think it's "over"...but I can hope, right?

Thanks all,
Sailingsenses
Click to expand...

Any sort of air leak at the PCV port can cause issues. The intake tube is connected to the valve cover after the MAF sensor, so it's just like running with a crack in the tube.

I went through the same thing during my engine swap, broke a PCV valve and didn't have one on hand, so I plugged the vacuum line but it still didn't run correctly. A new PCV and grommet fixed it.
 
Hi,

The hesitation and all else has stopped after the new PCV grommet was inserted. The new one was definitely ill-fitting or messed up to start with. As mentioned, the one before that was entirely rotted out. I think when the intake hose went to s***, it probably taxed that system and began a domino effect.

Actually, he didn't disconnect the battery; that way, I could continue test driving it (without resetting the computer).

I have driven it 175 miles and no CEL/misfires. I hope that did it, and that the crapped out PCV grommet didn't ruin other aspects of the engine. I learned from three years ago and did not continue to drive it with a CEL. I've also learned to keep checking the PCV annually, if not sooner.

I feel pretty sure it was the PCV...but I'm not going to rely on the fact that this is over.

I still plan on replacing the EGR and doing the Seafoam spray into the intake manifold. I wish I were expert enough to clean up the essential parts all by myself, brushing and all.

Thanks again, guys!
 
Questions:

1.) Spark plugs: The new ones didn't look that amazing after just three days. Not sure what they ARE supposed to look like, but maybe it's running rich and I need to do something? If so, what? Another reason to replace the EGR?

I did drive around for several miles to see if the CEL would come back on (or in anticipation that it would), and I guess the ill-fitting grommet didn't pop up for a while into that test drive. That may have caused the car to run rich. The plugs had some white residue at the tips already, just like the old ones. I will just replace them again in 10K, probably...

What should I be looking out for with a car that is running rich?

2.) Where do I get some new and super high-quality vacuum line hoses for this car? I figured it would be a great idea to start putting in new ones, everything that I can easily access, at least. How can I get some guidance on that? Sizes, and which spots? I am not versed in this at all...

3.) Do I bother to replace the fuel pump or the filter/sock? Would a bad pump produce its own CEL?

Thanks,
 
Last edited:
Sailingsenses said:
3.) Do I bother to replace the fuel pump or the filter/sock? Would a bad pump produce its own CEL?
Click to expand...

Replace your fuel pump housing... It has the high pressure filter built into it.

If you wait until it completely plugs up with crap then you will also burn out your fuel pump.

There is a few cells related to it but not specific... Don't wait for the cell and consider it "general maintenance"... just like our coils....

http://www.mazdas247.com/forum/showthread.php?123829616-How-To-Change-Your-Fuel-Filter-(lots-of-pics)&highlight=
 
Last edited:
Sailingsenses said:
Questions:

1.) Spark plugs: The new ones didn't look that amazing after just three days. Not sure what they ARE supposed to look like, but maybe it's running rich and I need to do something? If so, what? Another reason to replace the EGR?

I did drive around for several miles to see if the CEL would come back on (or in anticipation that it would), and I guess the ill-fitting grommet didn't pop up for a while into that test drive. That may have caused the car to run rich. The plugs had some white residue at the tips already, just like the old ones. I will just replace them again in 10K, probably...

What should I be looking out for with a car that is running rich?

2.) Where do I get some new and super high-quality vacuum line hoses for this car? I figured it would be a great idea to start putting in new ones, everything that I can easily access, at least. How can I get some guidance on that? Sizes, and which spots? I am not versed in this at all...

3.) Do I bother to replace the fuel pump or the filter/sock? Would a bad pump produce its own CEL?

Thanks,
Click to expand...

What plugs are you running and what do they look like? A white-gray color is pretty normal for a fuel injected engine. If in doubt, spend the 9 bucks on some NGK V-power copper plugs. The expensive platinum/iridium plugs only benefit longevity, the copper plugs take less energy to fire. The plugs are so easy to change on this engine that there isn't a need for plugs that last 100k. Replacing them now and then will prevent them from seizing too.

You can determine the fuel pump's health by observing it's waveform with a lab scope. But again, this equipment isn't easy to come by. I wouldn't worry about it, but I also get free towing from the AMA...
 
Please log in or register to reply here.

Similar threads

K
DFW floods - High water and car running rough now
Replies
11
Views
2K
katapaltes
K
BenjiHoggi
Protege5 won't idle after refueling (EVAP/O2 sensor issue?)
Replies
10
Views
2K
BenjiHoggi
BenjiHoggi
T
Rough Idle, Loss of Power and No CEL (2003 Protege5) - Solved!
Replies
15
Views
6K
BenjiHoggi
BenjiHoggi

Latest posts

Back