Freelander 1 1.8 emissions idle test fail - Finally solved!!

on torque go to graphing -graph type-line chart-y axis source-O2 voltage bank -ok -start loging.

Thanks Tony. Got it plotting ok. Interesting and will attach plots but all looked grim with trace up around the 700mV level at idle and looked ok at 1500rpm ish. Warmed up and took for a run and still the same. Took connector apart on o2 sensor 1. Cleaned and tweaked contacts and trace changed to all good!! So pic one is at start of test at idle, pic two is being revved and pic 3 is after contacts cleaned at idle.




Have I struck lucky? Will try again from cold, how long / warm should it be to kick in normal operation? Thanks for your help.

yep that's it with engine hot start data logging on one bank for accuracy ,rev it to 2k and let it idle ,if the wave go to 0 .0 v the o2 is shot

Tried again from cold. Can't repeat the fault in pic 1 above. All seems fine as far as I can see. No dropping to zero. Anyone had bad o2 connector fault?? Seems too easy!

andyfreelandy said:

Tried again from cold. Can't repeat the fault in pic 1 above. All seems fine as far as I can see. No dropping to zero. Anyone had bad o2 connector fault?? Seems too easy!

Click to expand...

Maybe the connector wasn't fully home, or had a foreign object between the contacts, which was displaced by parting them? Don't knock it if it worked.

Indeed - good bit of software though - £2 for bluetooth adaptor and £2.95 for Torque Pro !!!!
Will do mpg, fuel trim, rpm and more. Also, 0-60 times if you are so inclined !

That's a great result! And all from a bit of kit that would cost less than a new Lambda sensor

Great bit of detective work there

Friday MOT retest will tell what type of detective work it was!!! Having seen the change in waveform I think it is irrefutable but I could see no fault in the connector. I suppose it doesn't take much for less than a 1v signal to get lost in that environment!! Will be cleaning plugs, fresh fuel and a thrash when warm then ask for emissions test as soon as I drive in!!

Fingers crossed Andy

Just tested o2 again and flat 0v!! Peaks when revved so all is connected but no amount of contact cleaning or tweaking restores the good trace of yesterday!! Arghhh! Can the o2 behave intermittantly? Could be wire broken but not sure how to find it. Engine runs well with or without o2 it seems. Any brain waves please?!?!

O2 only connects to fuse and ecm. All checked and pins cleaned. No volts from sensor. Will try to get new one before Friday!!

Yes, sounds like the sensor is probably on the way out. Sounds like an electrical fault - broken wire may be? Is the loom connector intact? If it isn't, the replacement sensor will give the same problem.

Ok all wiring in car checked out ok. If you unplug and plug in sensor 3 or 4 times while engine running waveform 0.2v to 0.8v works until switched off then you have to fiddle again!! No fault codes. New sensor on order. Will try and get it to work for mot else will return when new one fitted. Tried to get working spare out of another car but won't unscrew. Suspect sensor doesn't look very old so hope it will shift more easily!

It's almost like you can jump start it by disconnecting and reconnecting!!

So - the MOT guy tried everything to get it to pass the emissions ! But every time the Lambda hit the right numbers the CO went high - like 2% and above.

O2 sensor didn't arrive in time and I monitored the oxygen pre and post cat sensors while he did the test. The front one was limping from 0v to 0.3v and the rear one occasionally dived towards 0v for no apparent reason. I serviced the car, put new fuel in it, gave it a good hiding on the way to the test centre and then drove straight in for the test but alas !!

Anyway, learning a bit about the 1.8K petrol and emissions - will be interesting to see if a new sensor (pre-cat) does the job and whether it cures the odd behaviour at the post cat sensor.

My money says it will - so fingers crossed!

You are on the money! Sensor turned up. Struggled but got old one out. Waveforms became text book. Ran back for re re test and passed!! So fast idle now 0.03 co and idle 0.2 co. Will log and publish o2 sensor waveforms now that it is working. Weird that my pic 3 above was spot on but didn't last. It was obvs the o2 sensor's last fling before it died. Will, of course, do an autopsy on the old one for information. Thanks for hints, tips and how to log waveforms from all who contributed.

The V6 makes a much prettier pattern!! Looks ok on the basis of what I have learned.

1.8 K series waveforms. Working O2 sensor. Pic 1 is 1000rpm. Pic 2 is 200rpm and pic 3is transition from 1000 to 2000rpm. For reference.

Those pesky O2 sensors going intermittent. Glad it's fixed now.