Rough idle situation
 

I was wondering if anyone else here has ever encountered anything like I just did in the last two days with idling problems. Yesterday, I pulled up to a stop light and started experiencing a terrible rough idle. It was practically jerking my car back and forth and felt like it was gonna shut off any second, but it drove just fine. My car was also a pain to start, it would take a couple second of turning over to actually start, so this morning I dedicated myself to finding what the problem is.

I started out by checking my plugs, which I just put in last week (NGK IX Iridium) so they were fine like I was hoping they would be. But just to check if it would make a difference I put in the Nology Silverstone ones I got with my wires. That didn't do anything as expected but it at least eliminated one possible cause.

So I put the NGK's back in and took off my Nology wires and made sure they were in good shape too, which as far as I could tell they were but I put on the stock ones anyway to see if it would do anything. Started the car, and no improvements. It was still idling like crap bouncing within the 500-800 rpm range, pretty much consistently being under 1k. So I put the wires back on and made sure all the grounds were tightly secured to eliminate that possible cause too.

So next I cleaned my air filter, which is just a K&N filter I put on instead of the stock air box, I even got designated K&N cleaner for it and made sure it was as clean as could be. Yet again, no improvements. So now I was under the impression that I had a vacuum leak somewhere, but it didn't seem very likely because all the little hoses I could track down were connected to their designated places.

By now, I was pretty stumped as to what to do, so I took my car to Auto Zone to get a OBDII reading just to check if it was throwing any codes (other than the "insufficient EGR flow" which has been there since I got the car) since my car doesn't show a CEL anymore cuz I took out the light due to the continuous EGR problem. Turns out there was a read error for some reason, so I couldn't even get a proper CEL reading for some reason. Being pretty pissed off by this point because my car is always doing something retarded like this I figured I'd just give up there and take it to the Mazda dealer tomorrow and let them diagnose it.

Then SOMETHING happened, I didn't do anything to it at all, but as soon as I pulled up into my driveway and came to a stop, I noticed it was really calm again like it used to be. My idle was back at a steady 1000 rpm and purring like a kitty cat. I parked it and sat there in confusion because I didn't understand how it could've fixed itself out of nowhere. I even made sure it wouldn't come back by starting my car back every five minutes to see if it would come back. Took it for a spin around a couple blocks and made a few stops just to make sure it would idle right, and it did. Came back home again, parked it and just accepted that fact that the problem is "fixed" ... even though I don't believe I did anything to fix it

My question then is, has anyone experience anything like this before and does anyone have a clue what the hell was going on with my car yesterday and today?

P.S. One thing I forgot to mention that MAY be a cause is that I usually put in 89 octane gas, which is Ethanol injected cause I live in Iowa and we have a serious surplus of corn so they decided to make our environment a little cleaner that way. However, a couple days ago when I was at the pump, I decided to throw in regular ol' 87 for a change to see if it may show gas mileage improvements or more responsiveness since it's pure gas and has no Ethanol or anything, it was pretty much a little experiement I wanted to give a shot. So I was thinking maybe my car wasn't liking the lower octane gas since it "got used to" the 89 I always put in since day 1.

Yet again, any input might help clearing my confusion ... thanks guys!

dude, i have been experiencing this seasonally, usually at the middle of summer and middle of winter, i think its heat and cold (but shit, i live in alabama it cant get past -5 in ultra rare occasions). As the matter of fact my rough idle just stopped this thursday after 2 weeks of being rough. I have no idea what causes this, maybe its gas, but if anyone has any idea please post it here.

i was thinking (if you put your own timing belts on) maybe they wern't aligned right, but it couldn't be that.

my fathers ram 2500, had a similar problem, it reved slightly under 1500 RPM and would zero out, then rev yet again on its own.... dont remember how it was fixed and what was doing it


i am stumped also

sorry

I guess the heat issue was also something that crossed my mind, but I didn't take it very seriously as it really didn't seem to make much sense. Iowa usually doesn't get TOO hot but lately (the last 4 days or so) it's been pretty damn hot and humid. Yesterday we had a heat index of 110 and the temp was close to 100 itself, so that's pretty groundbreaking for Iowa weather. I will say that it crossed my mind but it doesn't seem to make sense as a lot of Protege owners live in Florida, Alabama, Cali and such, where heat like that is quite frequent.

I'm at least glad to hear it's not only my car, cuz every time something starts screwing up I get so pissed cuz I swear my car's a lemon ...

Well, first of all stop wasting money on 89 octane. It's not helping.
2nd iridium plugs and nology wires aren't really helping either, just a waste of money, IMO.
Guess #1 is your a/c compressor on will bunp your idle up and down between
500 & 800 rpm.
Guess #2 is you probably just needed to re-set the ECU--do you know if Auto-Zone may have done it? Just a guess...BTW, your car will prolly never idle above 800.
I think it was just a combination of things.

Actually it goes the other way for me, I'm wasting money on 87 cuz 89 is cheaper here, cuz it's Ethanol injected ... so that's kinda the reason I always went with it.

As far as the plugs and wires go, I know they're not helping but I'm the kind of person that obsesses over little things like that. I got the wires thinking they would improve gas mileage as that's what Nology claimed, but that's clearly not true, and if I sold them I wouldnt get more than $80 for them so I'm just gonna keep them cause they look kinda cool.

The only reason I got iridium plugs is because when I had the Nology silverstone or stock plugs in my car would idle at about 2000 rpm once I first started it up and work it's way down to the 1000 range after about a minute or two. When I tried the NGK's they brought the idle down to a normal within 10 seconds, so I was pretty happy with the outcome of that.

I just wanted to clarify why I wasted money on all the things you mentioned, or save money in the case of 87 vs 89 octane. As far as the A/C goes, I made sure that it was off as that was one of my very fist guesses too. But the ECU thing might be it, since it's the only thing that makes any sense. However, you'd think that if the guy at Auto Zone did reset it somehow that it would've fixed the idle as soon as I left the place, and not once I got home. Or does the ECU need some driving around to reset? All he did was plug in the OBDII and gave it two shots at reading it, and he got two link errors so I gave up on that idea.

I guess the octane difference in the gas and the ECU are the two factors that might have influenced it so far ...

The ECU, to my knowledge, does need some time to process the new information.

Would it be possible that the extreme humidity we've been experiencing this week might have an impact as well? The only reason I ask that is because I've read about other members on msprotege complaining about rough idles during extremely hot and humid and cold weather.

Nope. Not heat or humidty.

Try wiggling wire bundles (especially to the MAF) to see if anything causes it to start to stumble.

Clogged injecter that cleared itself?

I don't know what you mean by "the continuous EGR problem" but your symptoms sound a lot like the symptoms I had with what the dealer diagnosed and fixed as "stuck EGR valve."

We had difficulty cranking and rough idle in that range. It eventually did kill the engine once or twice. It also manifest itself as bumping/roughness at low-throttle as well.

Dealer recommended induction system cleaning as PM...

All I meant was that I've had a EGR problem since I bought the car. I bought it at 3500 miles and it had a CEL for "insufficient EGR flow". I tried cleaning the valve and all that but it's still there, so that's what I meant by the continuous problem, cause I can't get it to go away. Maybe the EGR tube or the solenoid sensor that attaches onto the valve is busted. One or the other is messed up, but I don't have the money to try and fix it right now cuz other stuff always comes up ... \

I just got home after being gone for 2 months, my girlfriend has been driving my car lately and told me about 4 days ago it started the same type of rough idle you described (normal down to 500 rpm or less). It had thrown a CEL light so I borrowed my brother's diagnostic unit and checked it out. I had two codes, P0300 and P0506. The first is idle speed low, the second is cylinder misfires. After checking my CD manual, I tried removing the air filter and checked for loose wires/vacuum lines. All looked okay and the problem still exists, so I may be headed to the dealer (which I hate). Sometimes I long for the days of carburetors and easy troubleshooting! I'll let you all know what they find.

Uhm, the computer troubleshot for you. It is a 2nd cylinder misfire! Check plug, wire and injector.

misfire was the code I had first too. Then eventually there was another code that lead the dealer to the EGR (nt sure what that code was.

Nope, the codes I had were for general misfire (not exactly what it said, I am too lazy to look it up now) and low idle speed. Anyhow, Whoohoo!! Today I removed the EGR valve (which is one of the possible problems listed under the 0300 code) and found it was stuck in position. I hit it with some PB Blaster first, still was stiff so then I used some oven cleaner to remove the deposits, then lubed it with some WD-40. After moving it back and forth I installed it, fired things up and like magic, the rough idle was gone. If it comes back again I will just buy a new EGR valve and install it. I love having a car that runs properly!