BartleDoo

iTrader: (1)

Has anybody out there ever gotten an intermittent MAF error code (code 31 OBDI) and the front oxygen sensors turned out to be the problem? The car runs perfect without the MAF connected. With the MAF plugged in, the car has a huge loss in torque and also studders on acceleration. I read somewhere that the front oxygen sensors going bad has caused this before. Anyone replace the front O2's and have this problem disappear?

Thanks,
Kevin

Ali SC3

iTrader: (10)

check for bad wiring on the 02 sensors and maf. Im on standalone but one time I had a o2 sensor grounding out (wire was cut) and it would disrupt my map sensor signal and cause random stalling. you could try to unplug the o2 sensor at the connector to eliminate the possibility of a bad o2 sensor (you don't need to actually remove the sensor or the wiring or anything, just unplug at clip). try no o2 sensors and leave the maf in and see how it runs.

If you dont get anywhere doing that you could try swapping in a known working maf.
It wouldn't be the first time a maf bit the dust.

BartleDoo

iTrader: (1)

Yea, already did the maf so I know it's good, but if the O2s are unplugged wont it be the same as unplugging the maf. If you unplug either wont it just go into safe mode and run off of the ecu's given parameters and not read either maf or O2 sensors for input?

Ali SC3

iTrader: (10)

take this info on face value, im not 100% sure what exactly goes on, but there is a difference.
with the maf plugged in and the o2 sensor disconnected, i think it will still utilize the maf readings to look up the fuel/ignition maps, but it will not trim them at all (based on O2 data), so you could consider it running *safe* (without trim it should run rich), but it still knows how much air is coming in and you are getting proper timing.

now when you disconnect the maf sensor, you are basically in *limp* mode, because the computer has no idea how much air is coming in and will run a safe tune because it has no idea the proper fuel or timing based on airflow, it only has a rough idea off of rpm, which will not be optimal at all, but as most safety designed things it should run smooth.

I hope that made sense. like when I first went na-t I ran an safc on the stock ecu with no o2 sensors.. at all. my car was definitely not in limp mode, and received proper stock timing.

BartleDoo

iTrader: (1)

Well I'll give it a try in a couple minutes if I can reach the connectors easily from underneath. Then I'll let you know how that worked out.

BartleDoo

iTrader: (1)

It does exactly the same thing with the maf plugged in and the O2's unplugged as it does with the maf plugged in and the O2's plugged in. So, the O2's are probably bad, right?

Ali SC3

iTrader: (10)

lol, im not sure anymore, but I wouldn't say they are 100% bad if nothing changed. did you let it warm up completely after you disconnected? I should have probably told you to try resetting the ecu after disconnecting the o2 sensors to clear any learnt fuel trims from before.

After reading it again it sounds like you could have a vacuum leak. check all the vac lines/intake piping for cracks, and valve covers, if you have a large leak the air will bypass the maf and you could get the maf low voltage code (code 31 OBDI).

as for the o2's, if they are really old or unknown age its always worth it to replace them (think gas savings).

BartleDoo

iTrader: (1)

I did let it warm up completely. My ecu was reset the last time I unplugged the maf so it hasn't learned any fuel trims because I had it unplugged until attempting this. I had a vacuum problem when I first bought the car which would cause stalling with a consistent maf code 31 that never went away, but I believe that has all been taken care of. Also, I should have said the code was extreeemely intermittent and never even stayed on for a long enough period of time to pull the code until the last time it came up. If it was a vacuum leak like before I would think that it would stay on until fixed. That is what leads me to believe that the O2s are bad, but something within them is leading the ecu to believe they are working. Think about this. When I have the maf and O2s plugged in there is (was) no cel and the car runs badly. When I have the maf plugged in and the O2s unplugged it runs exactly the same way as with both plugged in except there is the O2 code. If the new O2s don't change anything, then I will continue to run no maf because I don't want to risk it running lean.

Ali SC3

iTrader: (10)

so its actually throwing the o2 code, thats good. your o2 sensors could be on their way out, a lot of times they are bad and don't set off the code till much later down the road.
might be worth a shot, it makes sense because even if you have a slight leak the o2 sensors/ecu should correct for it. I would do that and then start looking at the ecu if its not solved.

BartleDoo

iTrader: (1)

Yea, I got the universal bosch's for almost 50% off at advance so I'll put them in this weekend. My clutch started slipping this week too, so I have to order one of those too. Then I'm gonna beat on this thing until it dies and leave it on the side of a road...I wish I could do that