mike_980

I have a Mitsubishi colt with a gen 2 GSR conversion. Around 6 months ago (5000 miles) I installed an AEM wideband, the idea was get this fitted before I start playing with other stuff. Until a few months ago it was working perfectly and other than running leaner than I'd like on a hot re-start (difficult to avoid) my AFR always sat pretty damn close to 14.7 then down to around 12 with 0.7bar boost.

I installed a new head unit in the car which meant cutting up the wiring a little bit as my boost controller, turbo timer, head unit and wideband all run off the same harness which I made up and the following day around an hour into the drive I noticed that my my AFR was off the scale lean at cruising.

It's been like this since except it does respond to throttle inputs, if I blip it briefly then it comes back rich then immediately goes lean before the engine has even settled again. Sometimes on normal driving it will dance around for a while between 10-20 but never seems to settle.

The sensor is fitted just before the cat, at a guess maybe 18-20 inches from the turbo elbow. I've tried giving the gauge a ground directly from the battery which didn't help and I'm reasonably confident I don't have a leak exhaust side. I replaced the 02 sensor today but made no difference and I can't find an air leak anywhere. Car seems to run absolutely fine, at least no different to how it used to.

I've also tried to test the narrowband is switching with a multimeter but my meter doesn't seem to respond very well, it sits around 0.35v and does move around but I don't trust what it's telling me. Running the engine without the MAF or 02 sensor makes no difference, still seems to sit at lean at idle.

Any suggestions as to what would throw my fuelling out like this? Presumably the MAF or air leak?

Hi all, I have a Colt/Mirage which I have done a gen 2 GSR conversion on (4g93T). I have an AEM wideband fitted just before the cat which does nothing except for give me a reading inside the car. Up until yesterday I hadn't had any problems and it would happily sit between around 14.5 and 14.8 at idle then drop to between 12 to 12.5 under full load. Yesterday in 3rd gear under hard acceleration I got some hesitation. I looked down to see what my AFR was and I was maxed out lean - not even reading a value. Worse than that, even steady state cruising the AFR seemed to be mostly lean with the occational flick to 10 then back to lean. Today when idling at temperature the AFR bounces really quickly between 12-18 and just doesn't seem to be able to find a place it is happy although the engine feels, sounds and drives perfectly fine.

The plugs don't look too bad but they do have some evidence of lean combustion, they certainly don't look perfect and they have covered about 3000 miles.

Plenty of fuel is getting to the rail - not done an exact measurement but I have pumped into a bottle and the flow seems what I would expect.

My EvoScan cable doesn't work at the moment for some reason, so I checked the 02 voltage with a multimeter and it just seems to sit at about 80mV. I've only checked this at idle and after checking I looked at what the wideband was reading and it was maxed out lean.

The 02 sensor has 2 wires to it so presumably a ground and a signal. I did notice that when I checked the ground, I had 150Ohms of resistance. Is this value correct? The fact it was such an exact value made me think that it was going through a pull up/down resister in the ECU.

I haven't yet checked continuity between the sensor and ECU - does anybody know what pins I should be checking?