Lean fuel mix

[spanky2000]

Hi,182 recently failed test on emissions. Lambda 1.07 at 3000rpm. I have used a scan tool and all the main engine sensors appear to be functioning as they should while driving. I have had an intermittent problem with the engine dying underload (on one specfic hill only) and under light load now and again. This will happen for a bit then disappear for a while. Today I noticed that when it died both o2 sensors read low voltages (0.02). This would make me think it is fuelling. I checked the resistance of the injectors (16ohms) and it has new 'proper' plugs. Anyone any ideas? Thanks!

 

[RS Charlie]

How old is the front lambda sensor? If it's been replaced what brand is it?

The high Lambda value could be down to an exhaust leak but I would expect the car to drive OK.

 

[spanky2000]

Hi, original sensor I'd say. 125k on it if so. I had a look at the graph of the o2 and it switches on and off ok. Its a bit slow to alternate at idle but alternates much quicker at 3000rpm. In any case instead of the 0.1v to 0.9v it goes from 0.02v to 0.7v. I had a quick look at the post cat sensor and it either sits solid at 0.410v which would explain the mild lean lambda reading ot at other times its all over the place. Sometimes it mimics the pre cat sensor which would make me think the cat is goosed but apart from the last test lambda reading 1.07 the HC's were only 14ppm at 3000rpm (Irish test limit 200ppm) and CO 0.00% (limit 0.20%). Incidently, two months ago both the HC's and CO were off the wall until I added a litre and a bit of Lucas Heavy Duty Oil Stabiliser at which point they completely disappeared but Lambda was only 0.99!!

 

[R3k1355]

Replace the pre-car O2 sensor with a genuine item and go from there.

It's usually the main culprit when you have issues, followed by the cat and sometimes the engine temperature sensor.