So I was driving home from Duluth today when my car all of the sudden sounded super loud, I threw a P0171 - Fuel trim malfunction (A/F too lean). When it warms up it gets a little quieter. There is almost no exhaust coming out of my muffler so I am thinking that the header or uppipe or downpipe is loose. Could this be causing a lean condition? No back pressure would mean too much airflow, plus my turbo is not spooling good so it is most likely my header I think. My next guess would be that an intercooler tube came loose or my air intake came loose to the turbo, but this wouldn't affect my exhaust flow would it? I am running a VF39 with front mount intercooler and 565 injectors on a conservative tune. Its too late and cold right now so I will have to jack er up and look tomorrow morning.
I don't know about an actual lean condition, but a header problem probably could cause the O2 sensor to read different. Feed it some seafoam, and see if you get smoke coming out where it shouldn't.
Isn't that error code thrown when the intake air doesn't match the exhaust. Could be an intake leak, bad MAF or oxygen sensor as well as the above.
I would have to agree. I was battling this the past 3 weeks before I left for Australia...it's gonna be 106 tomorrow, and I have seen a lot of subies!!! Anyway, Since I didn't have a code for any shot sensors, I basically took my intake apart and put it back together. I cleaned the MAF sensor, made sure the O-ring was okay, tightened all the clamps and hoses down, and then gave it a couple cycles to learn. I also put in a bottle of fuel injector cleaner and made sure my fuel cap was on tight. I drove all over god's creation for the holidays, and it didn't come back. I probably put on over 500 miles of varying driving, from WOT to cruising and it never came back. So, I would say to check all your hose clamps...listen underneath for hissing (air leak). The maf is reading the air coming in, then some unmetered air is getting in before the 02 sensor. Since it doesn't match the ecu will try to compensate by dumping a bunch of fuel in. And that sucks. I noticed right away. My miles per tank went from 200-220, to back up over 300-350. That's just my $1.50
well just as I had thought....for some reason the header to uppipe connection went to hell on me. DOES ANYONE HAVE A HEADER-UPPIPE GASKET LOCALLY I CAN BUY ASAP???? 612-226-6063 Adam
