Gtorider510

I have a 2004 gto with a serious mystery problem me and my mechanic can not figure out.So here it goes....My cel is steady on about 80% of the time.It even flashes somtimes which i know is a bad misfire.The thing is that it clears the code by itself and stays off and runs super smooth like new.When Im on the freeway i can keep it off for a long time but when i sit at a red light r in traffic it comes back on real fast.The idle is really rough and it stinks like unburned fuel but as soon as i start moving agin it smooths out.i checked the code it throws and its running lean.I replaced the spark plugs tightened down my intake mani,cleaned my maf and even did a smoke test.Im stumped my mechanic said he cant figure it out and said dont bring this car back to my shop so im stuck now with a gto i cant even drive.It seems to b a low rpm problem because thats when it throws the code and starts idling rough and stinking like fuel.It comes and goes i can pull up to a red light and its smooth as butter but then i pull up to the next one and it starts running like **** agin.Also it has low power and bad mpg when the cel is on.Someone please help here im going crazy!

Blackbat23

Has the car been modified at all? Stock tune? Also does the code error say which bank is running lean? That should help you pinpoint at least which bank is having the issue. PCV connection secure? You said you cleaned your MAF, what did you clean it with? I know quite a few people that have had MAF issues that were solved with a proper cleaning.

Gtorider510

Its bone stock doesnt even have a cai are a after market exhuast so im pretty sure the tune is stock to.It says bank 2 running lean but stinks like its running rich when the cel is flashing.I cleaned it with proper maf cleaner.its weird because it comes and goes but the cel stays on pretty much all the time now

Gtorider510

Whats the pcv connoction? Ive never heard of that.

Blackbat23

I'm going to guess if it thinks it is running lean it is going to dump fuel to compensate, which is probably when you start running like crap. If it points to bank 2, you might want to check your plugs/wires on that side as a first starting point.

Gtorider510

I did thats what i thought to so i put all new plugs in and checked my wires to. The old plugs were white which im pretty sure means running lean because i had a 2001 SS that ran rich and the plugs were black

Gtorider510

I tested all the coil packs to and there all within proper voltage.

Blackbat23

Does it idle hunt when it runs like crap, kind of like a surge as if it can't stay at a steady idle? Might want to check your vacuum hoses as well. For leaks.

Gtorider510

Yea not real bad thought it stays at 500-400 rpm but the whole car shakes at idle and you can hear the difrence if you stand by the tail pipe. Vacum lines?wouldnt the smoke test show that problem? when the cel is off the idle is so smooth u cant even feel its running.

Gtorider510

Were is the pcv connection located?

Blackbat23

Should be a hose that runs from near the throttle body/air inlet to the rear of your manifold I believe. Might want to google it to see a picture be honest as I am going off memory.

Blackbat23

Also does an o2 sensor throw it's own code? I know I've read of other people having lean running issues and it turned out to be o2 sensors. Although it doing it intermittently is a bit weird I would think.

Gtorider510

Yes sometimes the o2 sensers go hywire but i thought o2 sensers were just for smog my ss burned them out all the time but it also had a full slp exhuast so maybe they were tuned out?the cel was always on but never flashed.

Blackbat23

In essence they monitor how rich/lean your air/fuel mixture is.

Gtorider510

Mhhmm i wonder why my mechanic didnt change them out theres only 2 of them right?

Gtorider510

Would a o2 senser cause a severe misfire to?i never thought they were that important.

Gtorider510

Do you know were the vac lines are?

Blackbat23

I'm not sure on that. Have you posted on ls1gto.com? Might get more responses from GTO owners that know a lot more than me.

And there are four o2 sensors I believe, two pre-cat and two post-cat. Two on each side obviously.

tom's2005gto

iTrader: (3)

you need to have a scanner connected to the obd2 port and read it live or data log and read it later. I'd suggest monitoring the o2 sensors. (there are four, two per side with two before cats and two after.

Gtorider510

So basically when the cel starts flashing i need to have the scanner pluged in because it wont store the codes its throwing?