Check Engine Light - Bad gas?
 

Would bad gas cause the check engine light to come on?
My car has been spuddering when idle and a couple times stauled on me yesterday while in idle. This was after I had filled up at the same station a couple times this past week. Check engine light came on this morning.

Go to AutoZone and have them read the CEL codes. They do it for free, and that will tell you why the light is on. Once you get those, report back and we should hopefully be able to tell you with more certainty what's going on.

I wouldn't think gas would cause the light to come on, but I suppose it could if it's causing a misfire or something of the sort .. so I guess it's possible.

I've had bad gas cause a misfire CEL before.. no fun! It has only happened to me with winter blend gas too.. ugh

Now I know to avoid most gas stations in Rochester.. only Hess is safe (there is no BP or Shell here :'( )

Fricking BP gas. I knew I shouldn't have filled up there twice in a row. Not sure if that's the cause, but I am assuming. Yeah - going to Auto Zone after work. Will post the code here later this afternoon to see if any of you can help. Thanks much !!!!

BP normally has really good gas. Maybe it's that particular pump that's having problems .. but BP is about all I ever trust anymore.

I've actually heard the opposite and frequently. I've always heard they had really bad gasoline. Now that I think about it, the pumps were running really slow last week, which means they were low on gas in the fuel tanks underground. Wonder if that could affect the quality of the gas? hmmm.

Just think of it this way .. if the tanks were low then you were getting the gasoline stored at the bottom. And when the gasoline sits there for a while, all the dirt and other impurities are gonna sink and build up at the bottom of the tank. So it may not be that the gasoline itself was crap, but rather that you just got the dirt from the bottom instead.

TOP TIER Gasoline Retailers:

QuikTrip
Chevron
Conoco
Phillips
76
Shell
Entec Stations
MFA Oil Company
Kwik Trip/Kwik Star
The Somerset Refinery, Inc.
Chevron-Canada
Aloha Petroleum
Tri-Par Oil Company
Shell-Canada
Texaco
Petro-Canada
Sunoco-Canada


sucks for me, because there isn't a single one of any of those anywhere in and around Rochester :(

Maybe it's an 02 sensor. How many miles are on your car? Have you ever changed the 02 sensor?

Auto Zone could not even bring up a code when they hooked up the CEL device. They said my computer was probably being fried. I know that is not the case. So as I was leaving the parking lot, the CEL went off. I've had no problems since (knock on wood) so I am thinking it was the infected gasoline from the bottom of the tank giving me grief as KrazyieFox implied. Going to fill up with plus gas for the next week and also gonna do a tune-up and oil change tomorrow. Have about 80,000 miles on it right now. Don't think it could be my O2 sensor. It only spuddered and stalled while in idle. It's fine while driving.

If the light was on and they couldn't read the code, they are MORONS. I went to Advance Auto Parts a week or two after my check engine light stopped lighting up and they were still able to pull the code (MAF voltage high).

If it's sputtering and stalling when idle, it could very well be that your EGR valve is stuck. Have you ever cleaned the EGR?

Never cleaned the EGR Valve. Good point though. I will check on that while doing my tune-up. What would you recommend cleaning it with? It would probably only be carbon deposits on it that would need to be cleaned off right?

People use brake cleaner on it, but be warned: I first cleaned mine at 66k miles, and now I have to clean it every oil change. Luckily, after the first time it's really easy. If you don't know where the valve is, it's right under the intake manifold near the throttle body. There are two 12mm bolts attaching it (not enough access to use a deep socket, but a normal socket should work as long as the head on your ratchet isn't massive), and there is a metal gasket between it and the intake manifold.

^^ A good how-to for you to write up at your next oil change Kansei. I know they got one on the other forum but it wouldn't be bad to have another.

after finals are over ;)

I want to make a 3rd gen maintenance guide that covers things like that, with links to how-tos for all the maintenance items as well as difficulty ratings and how often you'll need to perform them. Hell I could toss in an estimated costs savings vs having the stealership do the work too :)

Thanks for the tips. I'm assuming I'd have to clean it every oil change due to the dirt and junk leaching onto the brake cleaner residue?
That would be great on the how to's guides. I look forward to seeing that !!

https://www.mazda3club.com/how-tos-96/3g-protege-egr-valve-removal-cleaning-procedure-44475/

no pics for now, but I tried to make it descriptive :)

Kansei - you rock !! I was not expecting the full instructions on how to do this, but since you have - Kudos to you !!! This is exactly how a car forum should post. I might just wait until someone posts a non-residue cleaner where I wouldn't have to do this every oil change. I'm gonna ask around too. I'll let you all know what I find out.

I don't think the brake cleaner leaves a residue (that stuff evaporates crazy fast) but it's just a very harsh chemical.

It isn't actually confirmed that the harsh cleaner is in fact what causes the cleaning interval to get shorter and shorter, it's just what we're all guessing. I suspect that it could just be that it wears down more and more whether or not you clean it from all the carbon (the brake cleaner doesn't get everywhere after all) that flows through it.

I gotta remember to get some part numbers in the how-to.. like for the gasket, the revised EGR, etc.

oh no I'm such an idiot. I didn't realize this was in the Mazda3 forum!

carry on, maybe try getting the code read again, take it to the dealer, etc.

It's alright .. same procedures should still apply anyway. The EGR just might be in a different location and bolted up differently but the rest should still be helpful.

By the way, does anyone know if the Mazda 3 has the same EGR problem as the Protege5 does?

I haven't heard of any known EGR problem with the Mazda3. Plus, the engine is mounted the opposite way (intake manifold in the front.. and the intake manifold is plastic) so things are a fair bit different.

Oh well, it gave me something to do during a lull at work :D