6605stang

So at an autocross event a couple weeks back I stopped for gas at a crappy gas station prior and then 15 minutes later, I threw a p171/174 set of codes. Car seemed to be running fine though. Cleared it... it came back. Thought maybe I got some bad gas... putz'd the tank empty, filled with good gas... same thing. And since the beginning I started paying closer attention to my AFR gauge and I'll be honest, it's doing some weird things, but I'm not an expert to say what is SHOULD be reading at all times so I'm a bit confused. What do find odd is that it appears to be going full lean when I go to neutral after throttle (even very little throttle). And at idle it seems to be having a very hard time finding the right spot to rest (presumablely around 14.5). But honestly, this is the first time I've EVER had a potential fuel/lean issue with a car, so I'm (1) freaked out and (2) clueless. Below is a link to some video I took of my wideband gauge while doing some different driving around the neighborhood. Pardon the shakey vertical video, but it's the best I could do.

Thoughts? Ideas of what I need to check/try next?


PS - yes, my oil pressure gauge is disconnected.

Any helpful thoughts would be greatly appreciated!

JR

jwog666

check your fuel pressure, check and clean your MAF and check to make sure there are no leaks between your MAF and throttle body.

6605stang

Pardon my ignorance, but how exactly do I check the fuel pressure? And I did attempt to clean the MAF with a q-tip once already but to no avail. What's the best method to clean it? And aside from making sure everything is tight with no apparent gaps, is there any sure fire way to ensure there are no leaks between the MAF and TB?

Wondering if this is as simple as a plugged fuel filter...

jwog666

with a scanner you can monitor the fuel rail pressure pid and see if its in spec (around 35-40 psi non boost) and it should go up with boost or stay the same depending on your setup. the MAF wires should be inspected for fuzz and bugs, and i would clean with a non residue electrical contact cleaner, try not to touch the wires too roughly as they are fragile, as far as the leaks go , check to make sure all connections are tight and that there are no disconnected hoses, one other thing, check your air filter to make sure its not restricted (dirty) this will also cause a lean condition. with a supercharger you want to make sure you never go lean, or you could detonate and do some major damage to tour internals.

Simon1

You should really only be concerned with the AF under WOT. At idle and driving aroudn it iwll be erratic.

At idle, after it goes through the warm up phase, it should settle somewhere around 14.9ish. It will bounce around and move, don't pay it too much attention.

Under decel or letting off the throttle it will go full lean. It's all just fine. If you are running lean driving around, the computer will since it and throw a code.

WHat did the codes mean that the computer threw?

jwog666

p0171 bank 1 lean p0174 bank 2 lean, he is forced induction and needs to sort this out before he pings this engine down

Simon1

I agree. Those codes are generally thrown for something more related to drivability issues within the tune, dirty MAF, bad O2 sensor, bad tune, air leak. Something like that.

After watching the video it looks pretty normal.

The wideband is more for checking the tune under WOT. As long as he's in that 11.8 range under boost he'll be just fine.

808muscle

Totally agree. You have an air leak somewhere. Wideband, dont bother looking unless your WOT.

jpplaw

Kinda disagree, a wideband is good for spotting problems and diagnosing stuff, even during cruise. Like right now, I have spotted it dropping rich during cruise, so I then set the aeroforce to show fuel status. Sure enough, it is intermittently going open loop while cruising once in awhile then switching back to closed loop. O2 heater circuits are shot but not bad enough to set a code. Taking a long time to go closed loop on cold start too. Never would have known if not for the WB, since it still drives perfectly normal except for a slight drop in mpg.

I do agree that you cant obsess over just the cruise AFR readings though. A weird AFR with other associated symptoms is a good warning, but just numbers with no symptoms do not really mean much. I have my WB set to read in lambda (14.08-14.1= 1.00 lambda for 10% ethanol)

6605stang

I'm sorry, I didn't hear a word you said... I can't stop staring at your sig list of mods... excuse me... I need a minute...

j/k, thanks for the input. Gave the air filter and MAF a good clean today. Putting it back together shortly... we'll see if that does it. I'm thinkin 50/50 shot.