stubzie83 Posted May 31, 2011 Share Posted May 31, 2011 Hi all, Wondering if anyone could help. I got myself an OBD2 reader and hooked it up today to check it works and found some odd values. I found that my long term fuel trims 1 & 2 are at +8.6% which after some digging seems to be a bit high and means the car is running lean and the ECU is dumping in extra fuel to compensate. Should I be looking for a post MAF air leak or is this an acceptable value? FYI I had the air intake off at the weekend to change the spark plugs but did it all up nice and tight. I have noticed in the past few months that with the bonnet up when switching off the engine I can hear a hiss/squeak as the engine turns off that sound like air leaking from somewhere but had assumed it was just excess air escaping from the air box. I've also experienced a chattering/ticking noise at 4k+ rpms that has been there since a few weeks after buying the car. I thought this was a coolant issue (heather core valve flapping?) and swapped out the coolant, but the noise is still there. I'm now thinking this could be a symptom of an air leak. Does anybody have any thoughts on this? Thanks, Steve Quote Link to comment Share on other sites More sharing options...
Zugara Posted May 31, 2011 Share Posted May 31, 2011 you may have an air leak around the plenum, check all the bolts are tight... Quote Link to comment Share on other sites More sharing options...
stubzie83 Posted May 31, 2011 Author Share Posted May 31, 2011 Will do. I did a search and noticed that you had some similar issues. Did you get yours resolved? Quote Link to comment Share on other sites More sharing options...
Mark@Abbey m/s Posted June 1, 2011 Share Posted June 1, 2011 Steve, have you reset the ECU and then driven the car for a few days and recorded what it is triming? I have seen cars running up to 10/12% without any trouble. I think the O2 sensors detoriate over time so they sometimes trim unneccessary, this is one thing we do when we remap the ECU we reset the Injector K value to sync the cars O2 sensors to a known calibrated sensor it does make the car drive better we find. Quote Link to comment Share on other sites More sharing options...
stubzie83 Posted June 1, 2011 Author Share Posted June 1, 2011 Thanks for your response. I haven't tried a reset yet as I only plugged in my OBD2 tool last night for the first time. I will do a reset today and see if the values creep back up. The LTFT values were exactly the same for both cylinder banks. The ignition advance was reading 63.5 degrees as well but I don't know the significance of this. Would my replacement panel filter be affecting the values? I was under the impression that the O2 sensors just correct for differences between the MAF air flow/base map fueling by measuring the amount of O2 in the exhaust and trimming as necessary and that air flow in past the MAF shouldn't affect the trim value. Quote Link to comment Share on other sites More sharing options...
Mark@Abbey m/s Posted June 1, 2011 Share Posted June 1, 2011 Car runs closed loop mostly uses the airflow meter to give the base setting then trims via the front O2 sensors. Only wide open throttle is open loop. The car will self tune to the extra air flow but the AFR might not be what the car needs for best power/torque. I presume the ignition reading is a max number not a live reading? reset the ECU and report back your findings. Mark Quote Link to comment Share on other sites More sharing options...
stubzie83 Posted June 1, 2011 Author Share Posted June 1, 2011 Yeah the ignition timing reading was without the engine running so I'm guessing it must be a maximum. I have just performed an ECU reset so I'll see how it looks after a bit of mileage and report back. I'll probably do the idle air volume learning again later when I get home as well. Quote Link to comment Share on other sites More sharing options...
stubzie83 Posted June 2, 2011 Author Share Posted June 2, 2011 OK. So I think I managed to do a successful ECU reset yesterday using the pedal method. The CEL stopped blinking after the ignition went off and I started the car and it was gone so I'm assuming it went OK. I had a quick look with the OBD2 when I got home after 12 miles driving yesterday. I started the engine and at warm idle bank 1 LTFT was indicating +4.69% and bank 2 LTFT was +1.56%. I had another look today after another 25 miles and found the that at warm idle bank 1 LTFT is +3.91% and bank 2 is 3.13%. The O2 sensors have quite significantly different voltages though. The OBD report the following voltages: O2 sensor 1 bank 1 - 0.305V O2 sensor 2 bank 1 - 0.280V O2 sensor 1 bank 2 - 0.610V O2 sensor 2 bank 2 - 0.280V I'm a bit unsure as to why the sensor 1 values are so different (doubled/halved) as I would have expected them to be closer. Could one of them be knackered? Quote Link to comment Share on other sites More sharing options...
stubzie83 Posted June 2, 2011 Author Share Posted June 2, 2011 See post above for update Quote Link to comment Share on other sites More sharing options...
Sam Mcgoo Posted February 2, 2012 Share Posted February 2, 2012 OK. So I think I managed to do a successful ECU reset yesterday using the pedal method. The CEL stopped blinking after the ignition went off and I started the car and it was gone so I'm assuming it went OK. I had a quick look with the OBD2 when I got home after 12 miles driving yesterday. I started the engine and at warm idle bank 1 LTFT was indicating +4.69% and bank 2 LTFT was +1.56%. I had another look today after another 25 miles and found the that at warm idle bank 1 LTFT is +3.91% and bank 2 is 3.13%. The O2 sensors have quite significantly different voltages though. The OBD report the following voltages: O2 sensor 1 bank 1 - 0.305V O2 sensor 2 bank 1 - 0.280V O2 sensor 1 bank 2 - 0.610V O2 sensor 2 bank 2 - 0.280V I'm a bit unsure as to why the sensor 1 values are so different (doubled/halved) as I would have expected them to be closer. Could one of them be knackered? Any more updates on the out come of this? My sensor voltages are showing very similar values to yours. I have replaced both front sensors and there is no change. Quote Link to comment Share on other sites More sharing options...
jell36 Posted June 10, 2012 Share Posted June 10, 2012 sorry for reviving an old thread. Did anyone ever find out if the excess trim or O2 sensor voltages were ok? I have the same thing, all of my 02 sensors read .3V except for one which reads .6v and my long term trim is up at 8%. Just want to know everything is ok or if I should be looking for air leaks or new O2 sensors or cats. Quote Link to comment Share on other sites More sharing options...
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