idle problem and confusing CEL

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sneakypete

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2002 Protege5
I'm a delivery driver so I spend a lot of time in my '02 P5, and today while I was on my rounds, 2 things happened: first, the car started idling funny. It would be idling normally, then shudder and start to fluctuate between almost 1000k rpm and nearly stalling. Basically, it was revving up a tiny bit, over and over. It did the same thing every time at stoplights, idling normally for about 10 seconds, then little revs.
Then my CEL came on. I had the guy at Advanced Auto Parts read it b/c they'll do it for free, and he said it was giving a "Bank 1 too lean" code, but I don't know what that could mean since its an inline motor, is there technically more than 1 bank??
My only engine mods are an AutoEXE intake (essentially just a K&N cone filter with a horn over it), an ebay cat-back, and an MP3 ECU, all of which I've been running problem free for over 1000k miles, even more on the exhaust and intake. I'm resetting my ECU to see if it makes a difference.
Any thoughts would be greatly appreciated.
 
IIRC, Bank 1 refers to the first O2 sensor. somebody correct me if im wrong! but is that the only code that read out?
 
o2 sensor and possibly egr valve being dirty causing the weird idleing common issue. your idle is gona be wack for awhile when you reset the ecu
 
Thanks guys. It's not doing the messed up rev thing while it idles, now that I reset the ECU, but we'll see if the check engine light comes back on. And yes, that was the only code that he told me it threw; hopefully he didn't miss another one. What would that mean if only one O2 sensor is detecting a lean condition? Exhaust leak maybe? I don't know an awful lot about OBD.
And yeah, I keep meaning to clean my EGR valve, but on the very occasional days I have had off work (3 jobs don't leave me much free time), it's been too cold out to do the deed.
Thanks for the input, and any further ideas are much appreciated.
 
sneakypete said:
Thanks guys. It's not doing the messed up rev thing while it idles, now that I reset the ECU, but we'll see if the check engine light comes back on. And yes, that was the only code that he told me it threw; hopefully he didn't miss another one. What would that mean if only one O2 sensor is detecting a lean condition? Exhaust leak maybe? I don't know an awful lot about OBD.
And yeah, I keep meaning to clean my EGR valve, but on the very occasional days I have had off work (3 jobs don't leave me much free time), it's been too cold out to do the deed.
Thanks for the input, and any further ideas are much appreciated.
Click to expand...


i have the same problem, i replaced my front o2 sensor worked for a while i still have rough idle also (need to clean egr valve but no time due to two jobs)...but the o2 sensor does not mean an exhaust leak, the first o2 sensor is just reading below .45 which is why it throws the code...
 
Any idea why it might be reading lean? I mean, obviously it's probably just running lean, but is it anything I could fix with my limited abilities?
 
i have this EXACT problem right now, i changed my front o2 sensor but no luck :/

im gonna do the EGR next
 
Double check for vac leaks and make sure there is no air leaks in your intake. Bank one lean is telling you the engine is running lean. There is only one bank. If it was an o2 sensor the code would be either bank one sensor one(B1/S1), or bank one sensor two(B1/S2) lean.
 
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Air filter was just recently cleaned, but I'll check for vacuum leaks tomorrow. Resetting my ECU seems to have done the trick, at least for now. No more CEL, no weird revving, but slightly lumpy idle.
 
And for leaks in the air tube after the MAF.

i would shoot a shot of carb cleaner down the EGR 'inlet' (square hole at 6 o'clock position) on the throttle body (hold the throttle open and squirt into a long straw to guide it in ;) ). Wait ten minutes and start up. Ignore the smoke. It will go away. If that fixed it - then it is your EGR.

Clean your PCV too. On the high mileage engines it will clog with oil.
 
CEL: check engine light
ECU: engine control unit
MAF: mass airflow sensor
EGR valve: exhaust gas recirculation valve
 
Haha, point well taken sneakypete :) But didn't it feel good to help out a fellow P5 owner? (kiss)
 
So i just bought my Pro5 on friday in LA (3 hours away from where i live) it was running fine when i bought it. Once i got home, the next trip out the check engine light came on and i started having the same idle problem that everyone is explaining on here. Today i took out the EGR valve and cleaned it really well. I also replaced the air filter which didnt look to bad but it couldnt hurt. On the test drive after doin all the work the check engine light is no longer on but about once every 3 or 4 times i come to a stop and idle at a light, the engine still wants to dip to 100RPM or so and and jump back up causing a rough idle. Also i put some seafoam in the gas to further the cleaning process.....is there anything else i can try? Im taking it in tomorrow to have a full point inspection, was thinking about telling them to check my O2 sensor and possibly go ahead and swap that out. Anything else i should take a look at or tell the guys at the shop to look for?
 
Intake tube is probly cracked it will be right in the elbow if you don't see any by looking at it take it off for a better look
 
tweety2300 said:
Intake tube is probly cracked it will be right in the elbow if you don't see any by looking at it take it off for a better look
Click to expand...

sorry if im slow to pick this stuff up but which one of the many tubes would be the intake tube?
 
the huge tube from the airbox to the throttle body. Not one of the small lines, but the big ******* tube.
 
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