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Lambda Sensor Failure?

G

gasser

Just got it firing!
Joined
Feb 20, 2013
Messages
23
Location
Worcester, UK
My 8V 1200 sport has recently started to run very rough and after much investigation I appear to be no further forward, so any help or guidance would be much appreciated. Symptoms are:-
1. Unable to hold a constant throttle at low speeds - it miss fires, jerks around and almost 8 strokes.
2. On a number of occasions, the tick over 'sticks' at 2000rpm.
3. When under heavy load with a wide throttle opening, the bike initially accelerates, then bogs down at approx. 4000rpm before eventually clearing its throat and then accelerating correctly.
4. When using the upper rev range, the bike seems to run fine, its only when in the low to medium rpm band.
5. Symptoms are more pronounced when engine is cold or warm. When engine is hot, I can still feel it doing it but it is far less pronounced.
In summary it feels like it is running way too lean and is being strangled.
My local Guzzi dealer has plugged the bike into the computer. There are no logged faults or errors, its is running the most up to date map (has done since last service 3000miles ago). He did re-set some parameters even though he said they were within required parameters (I think, throttle sensor, lambda sensor and air temperature) and eureka; it ran perfectly on the ride home. However, on using the bike some 3hrs later, all the original rough running symptoms had returned.
Actions I have taken:-
1. Tank drained and fuel pump removed to ensure no water etc was in the fuel (nothing found)
2. Spark Plugs checked - no colouration on them at all (newly fitted some 700 miles ago)
3. Valve clearances checked - all correct.
4. Air box removed - no foreign objects found (running a K&N since service 3000 miles ago)
5. Injectors removed and visually checked for any blockages - nothing found.
6. Crank sensor checked - measured 697ohm - within tolerance.
7. Air temp sensor checked - measured 3.06ohm - within tolerance.

I also checked the O2 Lambda sensor. I got a reading of 0.01ohm's. Is this correct? According to the manual I have I should be able to measure 12.8ohm's at 20c. Ambient temperature was 25C. Is this the culprit?

Any help would be much appreciated. Thanks
 
Hi Gasser,

A mate of mine had a very similar issue on his Griso recently. Turned out to be the spark plug caps were damaged (from a routine service) and were sparking/shorting to the surrounds instead of inside the cylinder head. This in turn toasted the O2 sensor (running way too rich) which, in turn, made his bike run like a pig (as you would expect).

Repairing the damaged spark plug caps and replacing the O2 sensor did the trick. Not to mention fuel consumption corrected itself, afterwards.

Worth looking into this as you state the plugs were replaced some 700 miles ago. Is this when the trouble started?
 
Hi Tony. The symptoms were present before I changed the plugs. My local guzzi mechanic was suspicious that it was the plug leads/caps, but on checking visually plus via his computer diagnostics no problem in this area was found. What perplexes me is that when I rode the bike in, running like a dog, all he did was plus his diagnostic tool in. Nothing was physically touched on the bike. He refreshed the parameters using his laptop, and then the bike ran beautifully, possibly the best it has run in quite a while, only for it to revert to miss-behaving again when I used it some 3hours later, and continues to do so. Having conducted my own, admittedly crude tests over the weekend, the only specification that appears to be 'out' is the O2 sensor. According to the service manual (the 2v Sport version - but I understand the O2 sensor is exactly the same as the 4V/8V), I should be getting 12.8Ohm's across connector pins 3&4, when all I can measure is 0.01Ohm's. I am no expert, but this suggests there is no resistance present suggesting a broken heating circuit within the O2 probe? I am very reluctant to spend £120 on a new one as I am not yet convinced this is the root cause, especially as no error code for the O2 sensor was found during the diagnostics. Should I accept that because no O2 sensor error code was found within the diagnostics, the sensor must be good and I should ignore my measurements/findings?
This is beginning to drive me nuts!
 
As Tony says it sounds typical of plug caps. Why did it run after the parameters were re set? Who knows? Perhaps that just made the conditions in the combustion chamber more amenable and easier for the spark to jump the gap at the plug.

A shorting plug cap won't show anything up on the diagnostic tooling. Its a tool, not a crystal ball! Its not designed to miraculously tell the person holding it what is wrong with the bike. Would you expect to plug it in and have it tell you you have a flat tyre or that the steering head bearings need greasing? The purpose of Navi/PADS or the other aftermarket tooling is to be able to check and adjust certain items of an electronic nature. It won't tell you if the spark is shorting to earth.

Checkng that is very easy. Simply take off the HT lead covers off the rocker covers, start the bike, look and listen. You can usually hear the snap of the spark shorting to earth and most times it will be visible, especially if you do it in the dark. Apart from anything else checking and/or replacing the caps is cheap! Just do it! If there is an issue with the caps it'll cure it. I personally would use NGK SB05E's and snip the screw fitting off the end of the HT leads. Yes you have to bend the leads to get them under the covers but they cure the problem of the easily damaged stock caps. Having said that I don't think I've had one fail for a couple of years now but removing them does require care and sometimes, even if removed 'Right' they still seem to fail.

Pete
 
Thanks for the insight Pete; and indeed you too Tony. I had dismissed the plug caps/leads due to the local guzzi mechanic being adamant that if they were shorting it would show up on his diagnostic tool when he plugged it in. I have always removed the caps using the zip tie around the cap head method, but as you say, perhaps they still do fail. I have now dismissed the O2 sensor as I disconnected it and on running the bike, the symptoms were exactly the same; so I am now assuming that the O2 sensor is ok.

I will run a spark test in a dark room a little later and let you know how I get on.
 
Quick question Pete. As you say the NGK caps are an inexpensive part so it does make sense to change to them, but what method is used to secure the existing spark lead to the existing cap? Is it a push fit or does it screw in the traditional manner? Probably a stupid question but do not want to run the risk of damaging the leads.

Thanks
 
The only special thing about the HT leads is that they have little screw in ends that, well, screw in to the later plug caps. If you want to use the NGK's you need to snip off the threaded brass end of the lead and then just screw the NGK cap onto the lead.

Some bikes. Stelvios specifically, may have leads that are a tad too short after the end is snipped off. No big deal, just buy a metre of HT lead and replace them both. Its not expensive or difficult.

Pete
 
I have checked the leads/plug caps with bike running in a dark room and could not find any signs or evidence of failure. However, have ordered the NGK SB05E's and will fit when they come in and advise the outcome. Fingers crossed this will cure it.
 
gasser said:
. I have now dismissed the O2 sensor as I disconnected it and on running the bike, the symptoms were exactly the same; so I am now assuming that the O2 sensor is ok.
Click to expand...

Sorry if this is a dumb question, but if your bike was running well and you unplugged O2 sensor it would then run shite, right.
So if it is running shite, and you unplug it - and there is no difference, it would indicate to me it was faulty.

ie. When a 6 cylinder car is running on 5, disconnecting 1 plug lead at a time and then replacing it will indicate which plug/lead is faulty. If it drops onto 4 cylinders when you remove a lead, you know that cylinder WAS working fine.
WHEN NOTHING HAPPENS, YOU KNOW THAT INDIVIDUAL CURCUIT HAS A FAULT.
 
Ghezzi, your point is spot on; some times you cannot see the 'wood for the tree's'.

Quick update, I have now replaced the plug caps and also the HT leads from each coil, and it has not made a scrap of difference. My symptoms remain. On the up side, at least this has ruled this notorious element out.

This brings me back to my original point, the lambda sensor. I have now cross referenced the sensor and it is the same for both the 2V sport as well as the 4/8V. According to the specs I have for the 2V, I should measure 12.8Ohm's across pins 3 & 4, yet I only get 0.001Ohm's. So is this the problem? What is conflicting with this though is that according to the diagnostics, there are no error codes on the lambda sensor; so if no error codes, presumably it is working ok? Does the diagnostics only assess/measure if the sensor has the correct voltage and not the resistance? So if voltage ok, ECU 'brain' thinks it is ok?

As I understand it, a faulty Lambda sensor will cause the ECU to default to running the injection rich? This may be consistent with the bike flying once above 4,500 to 5000rpm when it uses the fuel its being given, but running rough below that when it gets more fuel than it needs?

Trouble is a replacement sensor is £120 so its a big risk just buying one to see if it fixes it without having any real evidence to back this up!

Bizarre.
 
Sensors are available for a lot less off fleabay. My personal feeling is the problem lies elsewhere. Has your bike still got its original exhaust system? If so has the Catalytic honeycomb become clogged or come loose interfering with flow? Just a thought.

Pete
 
There was a case recently on the Wildguzzi forum of a Belgium guy who had a similar problem which was down to badly machined lambda threads in the exhaust . This caused damage to the sensors themselves when they were fitted at the factory.
http://wildguzzi.com/forum/index.php?topic=63167.0
You do really need some diagnostic software.
 
Had an interesting discussion with a NTK technician this morning, and on stating that I could not get any resistance reading across the two heaters wires on the Lambda sensor he pronounced it as 'dead' and no longer fit for purpose. He was of the view that this was causing my running problems, but was also perplexed as to why no errors were found doing the original diagnostics.

Well I have waved the white flag of surrender and taken it back into my dealers today. At least I was able to produce quite a comprehensive list of what has been checked/tried and eliminated up to this point. The mechanic stated that if there are still no errors showing on his diagnostics, and he cannot find any other reason for it, he is going to swap my lambda sensor with one off a new Stelvio in the showroom to see if this has any effect, which I thought was very fair. He did say that he had never experienced a problem with one before and therefore never replaced one.

I will keep you all posted on the outcome.
 
With Centurion or VDSTS you can observe the lambda voltage of the running bike. If there is no change in voltage then the sensor is faulty. I would hope the factory software could do the same.
 
Well the bike has now spent two days in the dealers being thoroughly checked out with static and real time diagnostics. The Lambda sensor was specifically checked and is working perfectly. Suffice to say, nothing could be found wrong with the bike. Even more frustrating is that on road test they could not replicate the symptoms, yet within half a mile of me collecting the bike, it was up to its usual rough running, unable to take full throttle at 4000rpm 'tricks'.

I have owned the bike for over 3yrs, having done over 16000 miles, so I know its not running right.

I have no idea what to do now.
 
I have a 2012 Norge with 18,000 Kms on it. I did in fact pinch a Spark Plug lead, and understand those symptoms. It was really easy diagnose from the snaping sound at the valve cover. I do not believe this to be your problem.

I too have experienced EXACTLY the same issues you are currently struggling to overcome. Try this:

1) Check the 10 mm exhaust pipe nuts at the head. If loose it could burn a new O2 sensor again.

2) Change the plugs

3) Install new O2 sensor(s) as required.

4) Test drive and be happy.
 
Something else to consider...

Wire loom under tank/airfilter by left pot. May be touching.

Water/Condensation inside clocks.

Both produce symptoms like described I've read here.

Also GuzziDiag is free software that may help diagnose Lambda issues.

Cables are cheap too:

VAG OBD2 II 409.1 KKL USB Car Diagnostic Scan Tool Cable Com Fault Code Reader

Fiat , Alfa Romeo or Lancia 3 Pin OBD to 16 Pin OBD2 Adaptor Diagnostic Cable

Both for around £15 :)
 
Thanks for all your suggestions and tips. Plugs had been replaced, the dealer assessed the O2 sensor as being fit for purpose using the diagnostics. He also compared my O2 sensor with one off a Stelvio NTX he had in the showroom and according to him both matched perfectly. This tends to dis-prove my theory that it was the O2 sensor, which I was convinced was the source based on my own research
To be fair, the bike is better than it was, although definitely not right. I took a non-motorcyclist pillion for a ride and she too could feel it miss behaving, so I know I am not going mad.
 
I had similar intermittant simptoms on my Stelvio, nothing showed up on my VDST took it to Haywards and they identified the RPM sensor. They sold it to me and I fitted it myself, problem solved, did your dealer try changing the rpm sensor?
 
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