OK, so exhaust leaks that lead to CEL.... that makes it read lean or rich? Before I got the leaks fixed, I was getting both extremes and it was running stupid rich. Now it's popping the too lean code code. So.... do I still have a small leak pre-sensor, or is the sensor plugged from running a few weeks as stupid rich.
MAPP gas the old sensor to clean out the carbon. Then just reset the fuel trims. Should fix it up.
MAPP?
An exhaust leak will make it look like there is excess oxygen in the exhaust, which it will interpret as too lean.
Fun fact, your AFR will fly over to full lean during a spark cut, which can send you on a wild goose chase after fuel system problems that don't exist when you should be looking for ignition problems. Ask me how I know.
GameboyRMH wrote: Fun fact, your AFR will fly over to full lean during a spark cut, which can send you on a wild goose chase after fuel system problems that don't exist when you should be looking for ignition problems. Ask me how I know.
Hey, I know that one too!
Mapp gas = like propane but hotter.
Exhaust leaks pre o2 sensor will cause lean readings
So there's still a leak. Damnit. I got 3 weeks to get it found and sealed.
I have now been over this thing top to bottom and can find no sign of a leak. Yet, on start up I still get a whiff of exhaust come through the vents which tells me there is one. How the hell do I find this little bugger?
I would have thought O2 sensors are too sensitive to be hit with MAPP gas but you learn something new every day. I guess they're exposed to EGTs after all.
Bobzilla wrote: I have now been over this thing top to bottom and can find no sign of a leak. Yet, on start up I still get a whiff of exhaust come through the vents which tells me there is one. How the hell do I find this little bugger?
Can you do a smoke test through the tailpipe?
Sadly, I no longer have the awesome access of all those types of tools. That's about the only thing I miss not being at the dealerships. Literally, ONLY thing.
restrict the exhaust tip with something to build back pressure, then search for leak. If you start with a cold engine you can simply run your hand over the exhaust until you get a puff of hot air. With enough back pressure you may even be able to hear it making a hissing sound.
Cracked manifold ? Exhaust leaks should not be that hard to find.
TGMF wrote: restrict the exhaust tip with something to build back pressure, then search for leak. If you start with a cold engine you can simply run your hand over the exhaust until you get a puff of hot air. With enough back pressure you may even be able to hear it making a hissing sound.
this has been a proven technique for me when looking for exhaust leaks
iceracer wrote: Cracked manifold ? Exhaust leaks should not be that hard to find.
I just installed a complete header/cat to go with the cat-back. Had a leak, fixed it. Had anotherleak, fixed that. I remember how much I hate headers for this crap.
drill a 1/2-3/4 inch hole in a tennis ball stuff the bastard in the tail pipe start and feel around every seem for a jet stream of hot air. you could use a small candle too watch the flame but that can burn badly dripping wax.
ssswitch wrote: I would have thought O2 sensors are too sensitive to be hit with MAPP gas but you learn something new every day. I guess they're exposed to EGTs after all.
Since the rear sensor regularly sees very hot ammonia, MAPP gas is easy.
44Dwarf wrote: drill a 1/2-3/4 inch hole in a tennis ball stuff the bastard in the tail pipe start and feel around every seem for a jet stream of hot air. you could use a small candle too watch the flame but that can burn badly dripping wax.
Or use a spray bottle of soapy water- like when you look for leaks in a gas line. That's how we do it.
That might work until every thing gets hot.
Spray a little MO, ATF or something in the intake, enough to make smoke.
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