Mechanical Problems/Vehicle Issues and Fix-it ForumIf you've got a problem you just can't figure out, a noise you can't diagnose, or a Check Engine Light that won't go away, ask about it here!
ok everyone hope someone can shed some light on this. 2002 civic lx AT coupe. 100,000+ miles. a few weeks ago i started experiencing CEL with some rough idle and loss of power when accelerating. i changed my oil abd spark plugs. a few days later same deal. it first started one day that was really hot and i was in traffic. so a buddy told me change your O2 sensors. did that. same CEL. now if i'm driving highway with no traffic the car runs fine. it's if i'm doing city driving and there's some traffic it happens. i did a ECU diagnose with a code reading of P0420. emissions.
a few nights ago i was on the highway and ran into some traffic. when i pulled over to check the engine the manifold/converter was cherry red. i let it cool down for close to an hour, reset the ECU and it was fine until i got home. i was thinking maybe my converter is done or clogged. when i called the local muffler shop)very reputable). the old man told me he'd get back to me because his book was showing 2 different converters for my year vehicle. when i called him back he said it was in the $500 range for a new one replaced. then he asked me why i thought it was the converter. i told him what i just wrote. he said it sounds like a bad fuel sensor not the converter. i told him that i had done the diagnosis and he said sure youre gonna get an emissions code if you're dumping fuel into the engine. that didn't make sense to me. why would the converter get red with too much fuel. wouldn't the engine bog out if something's dumping fuel?
temp is normal even when it heats up. haven't checked the air filter. no full tune up just oil, plugs and O2's. no visible obstuctions in intake or exhaust. i assumed the plugs came gapped. they are torqued to specs. but the problem first happened before the plug change.
would a bad fuel sensor give me an emissions code and cause the engine to lose power and cause the manifold to turn cherry red hot?
No, your mechanic is right. The mani will get ridiculously hot if the motor is dumping too much fuel. That's why seriously built motors run EGT (Exhaust Gas Temp) sensors, it's a quick indication that an engine is running too rich or too lean. Too rich can seriously bump up the temperature of the exhaust, by as much as 2-300 degrees. That's why your converter is glowing a nice cherry red.
Rough idle and crappy power are also two indications that you're dumping too much fuel. Sounds like your ECU has a fault and it's dorking up your LT fuel trim.
Our ECUs are a "learning" ECU. In otherwords we have two types of fuel adjustment curves, or "trims", long term and short term. After an ECU reset, you car uses a Short Term fuel correction (fuel trim) or adjustment to maintain the desired AFR, dependent upon engine load vs RPMs (MAP vs RPM), and other sensor variables that the ECU takes into consideration. The ECU then takes the ST Fuel Trim and uses the trends it sees there to write to the Long Term fuel trim.
It sounds like the ECU is dorking up the ST/LT fuel trim corrections and dumping way too much fuel. Unfortunately, this is going to be a dealer fix only, unless you swap the ECU and either get your key flashed for the new ECU, or swap the ECU, lock cylinder, and appropriate key. I'd take it to a dealer.
I initially thought it might be a stuck injector, but since you said it's fine right after you reset the ECU, and you replaced both O2 sensors, it's got to be something in the ECU.
it could also be a loose O2 sensor. since i have not been able to properly tighten the bottom one. i will be torquing them both tonight. if that doesn't work i was told by my g/f's dad who's a mechanic to check the fuel sensor and fuel pump.
hopefully it's not a dorky ECU. but i have considered that.
What fuel sensor are we talking about? We don't really have a set "fuel sensor". The ECU controls the injectors by using a fuel map hard-coded into the ROM. Plus it's not going to be the pump. You're getting too much fuel, not too little. Unless the pump circuit is shorted somehow to throw like 24 volts at it (you would hear the pump constantly for a day and then it would die), it's not going to throw too much fuel.
Didn't know your O2 sensor was loose, that may be it, but I doubt it since you were having this problem beforehand. Do you have a decent OBD2 scanner? They're like $70 on Ebay and you can use them to read your LT/ST fuel correction and that will help you diagnose the problem better before taking it to the stealership. That might not be a bad investment before taking it in for diagnosis. That way if you do take it in, you save the dealer some time (and you labor charges) by having checked several things first.
O2 sensor torqued. drove around for a bit. CEL came on. i'm gonna try and get to a buddy's garage this afternoon and have it diagnosed. this is very frustrating.
That may be the cat being clogged then. Pull it off and shake it. If it sounds like a maraca, then the element has busted loose and you need to either replace it, or convert to an EX exhaust set-up and run a spark non-fouler to trick the ECU into thinking a cat is there. That's if you don't have to worry about emissions.
i think so too. the CEL comes on but there's no loss of performance or anything. i only drive the car to work and back, so if the CEL comes on i just reset it before i drive again. but like i said if it's really hot and i'm city driving for too long with the CEL on then the manifold gets really hot.
ok everyone hope someone can shed some light on this. 2002 civic lx AT coupe. 100,000+ miles. a few weeks ago i started experiencing CEL with some rough idle and loss of power when accelerating. i changed my oil abd spark plugs. a few days later same deal. it first started one day that was really hot and i was in traffic. so a buddy told me change your O2 sensors. did that. same CEL. now if i'm driving highway with no traffic the car runs fine. it's if i'm doing city driving and there's some traffic it happens. i did a ECU diagnose with a code reading of P0420. emissions.
a few nights ago i was on the highway and ran into some traffic. when i pulled over to check the engine the manifold/converter was cherry red. i let it cool down for close to an hour, reset the ECU and it was fine until i got home. i was thinking maybe my converter is done or clogged. when i called the local muffler shop)very reputable). the old man told me he'd get back to me because his book was showing 2 different converters for my year vehicle. when i called him back he said it was in the $500 range for a new one replaced. then he asked me why i thought it was the converter. i told him what i just wrote. he said it sounds like a bad fuel sensor not the converter. i told him that i had done the diagnosis and he said sure youre gonna get an emissions code if you're dumping fuel into the engine. that didn't make sense to me. why would the converter get red with too much fuel. wouldn't the engine bog out if something's dumping fuel?
please help. thanks.
ps...this is the post that sounded similar to my problem though my idle just drops. I don't know if it's "rough", just sounds like something is "stuck" and even with the pedal to the metal, it just stays at 20 mph. My Civic also runs fine in smooth moving traffic, but any creeping along or sitting at very long lights seems to provoke the problem.
still no fix. it went into the rough idle and no power 'safe mode' today again on the way to work. seems that if it's really hot out like today and i have the a/c on it does this. i have the ODB2 with me so i plugged it in. besides the 2 po420 codes it also had a p0361 code if i remember. which is ignition malfunction/timing. which makes sense since in 'safe mode'.
i guess i'll stop trying to DIY since i can't find any info online and take it to a mechanic i know.
changed the O2 sensors to OEM. CEL came on again. could it be the PCV valve or EGR valve? if not, the only two other fixes would be the cat is bad or the PCM is bad, correct?
