Power loss - LM

Had the Le Mans for a couple of months now. Generally love it but I’ve noticed on the last few rides that I get a momentary loss of power at cruising speeds 70 - 80 mph. Also it stalls occasionally at traffic lights. What’s that all about then? I use Shell V Power fuel if I can and it came from a dealer who gave it a full service before delivery (I assume).
Oh yeah it’s got a PC III fitted as well but no other mods.
Any ideas?

couple of things to check

  1. Battery any low battery will give weird things

Copper grease on the lambada sensor in the l/h head under fairing

inlet rubber cracked I had that it LOOKED ok but would cough at low revs especially after a hard run and sometimes cut out from lights as I pulled open the throttle I found it after a week of looking and head scratching

Ah, could be the inlet manifold. The outer part is looking a bit ropey. A warranty item do you reckon? Might be hard to persuade them…

I’ll check the lambda sensor as well. At risk of sounding thick, what does it do exactly?

The ‘Lambda’ sensor is located in the crossover and measures the o2 in the exhaust gasses in closed loop fuel injection sytems. The earlier v11’s were not fitted with one and run on a open loop system.
The v11 have an engine temperature sensor located in the cooling fins on the left hand head (between the jugs). Earlier big block fuel injected guzzis had a different style temperature sensor fitted in the left hand rocker cover.
Any one of the fuel injection sensors or connections in the fuel injection/ignition circuit could be causing the problem.
You could test for intake leaks with the engine ticking over spray inlet with wd40, or an unlit blowtorch and listen for a change in engine speed.HaydnR2013-06-04 00:26:45

Sorry …heck for an ol fart like me tis but a sensa…

Unlit blowtorch could be fun if it backfires. Rubber inlets arn’t too expensive and a lot easier to change in warm weather.

Well, tried the blowtorch trick and still here! No change in engine rpm, so probably not the rubbers. Try the sensor next. Is it something that is known to fail?

Weeel yeh it can fail OR just need some extra help to creat an electrical cct, I put coppergrease around it. Check the PCIII as well. I had a hesitation spot at low revs which is very common due to how they set the ECU to cover emissions. I had Twiggers re do it and after the open pipes, coppergrease around the sensor and new inlet rubbers all is well

OK, Confused of Cardiff here: according to the workshop manual (and HaydnR), the Lambda sensor is on the crossover, but I can find no evidence of it at all (at least, no electrical connection) and wondered if this was a pre-sensor model (2003 - mine’s a 2002). GB - it would have to be in the exhaust system somewhere, surely, as it actually samples the exhaust gases, rather than being attached to the cylinder head…Despite the blowtorch test being negative, I have my suspicions so will investigate further.It’s not a major problem, but a bit irritating nonetheless, so I would like to fix it

No the 2002 does not have one in the zorst, there is a sensor in the head lh side you have to take off the fairing… It was me misleading it is not a lambada but some other sensor…

That will be a temperature sensor, which is why it’s worth while putting copper grease under it to improve the thermal conductivity to the sensor.

Ah ha! OK I’ll try that this evening. I am therefore assuming that lack of lambda sensor makes fitting a Stucchi crossover much easier when the time comes…
Time to start saving

do the ecu’s on these have eobd output, would be much easier to connect up and read the values of the sensors etc and spot whats wrongalso have the fuel filters etc been done to ensure no blockagesI presure the exhausts dont have cats in them?

Yep it does my Stucchi has an 'ole in it for said sensor and as i got it 2nd hand = chaep I had to pop to Halfords to get a plug to bung up said 'ole.

Tell you what on mine I swapped out the fuel filter, a fairly easy job if a bit of a faff, the dealers told me they had rarely actually changed one of these as the huge filter under the tank is designed for a car…a V8 no less and technically good for well over 30k miles. BUT with modern (crap) fuel the difference was noticable and just to check I flushed the old filter, there was loads of that red crap in it.

By the way any fuel filter with the right size spigots on it that is round will fit… Bro in USA gets his from a car spares shop …Guzzi ones are megga bucks BUT I think Motomecca and possibly Gutsibits have car type ones cheaper that fit OK.

I got the bike from Motostrada so I am hoping that the filter was at least checked if not renewed prior to delivery…
Will be in touch with Gutsibits and Muzzi when I’m in a position to get a crossover.

2002 are pre lambda sensor. All v11 have 4 sensors and 6 actuators (late model v11 also have a lambda sensor):

Throttle Position Sensor (TPS) this tells the ecu what postion the throttle butterflies are in and then ecu computes how much fuel to add.If these go out of calibration the bike will run rough. The tracking on the flexible circuit board inside the sensor can wear causing dead spots in power. Located top of right hand throttle body

Crank sensor. tells Ecu crank position for ignition and injection timing. When these fail the engine will cut out, a failing sensor could begin to break down when the engine gets hot, a poor connection could cause intermittant power loss at any time. Located just forward of LH cylinder

Air and Engine temperature sensors. when these fail the bike will run but fuel consumption will be poor and the engine will run rough. Air temp ensor located on front of airbox above right hand throttle body. Oil temperature sensor located in the left hand cylinder head between the cylinders.


2 coils(plus leads caps and spark plugs) unlikely for both to fail together which would cause complete loss of power but either side could fail on any of the components giving noticeable reduced power and stalling.

Fuel Pump. failiure of the pump will cause the engine to cut out.

Injectors. unlikely for both to fail at the same time, power reduction if either fail.

Tachometer. using the signal from the crank sensor the ecu controls the signal to the tachometer.

With diagnostic equipment the sensors can be monitored and the actuators tested to assist diagnosing component failiure. You can also view any faults on these stored in the ecu log.
Well worth getting a diagnostic setup if you plan on keeping/maintaining the bike yourself see this post on the v11 forum for further info http://www.v11lemans.com/forums/index.php?showtopic=17865&hl=

If not get a guzzi/aprilia dealer to check diagnostics with their axone/navigator equipment.

The fault could also be elsewhere.

Ignition key switch
Kill Switch
side stand switch
fuses/relays relating to the fuel pump/ecu (original siemens relays known for problems, precautionary measure replacements from pyro dan http://www.dpguzzi.com/ )
Connectors to any of the above

failed inlet rubbers/leaking exhaust clogged fuel filter are more likely to cause a constant rough running cough or splutter.

Crikey Haydn! I think I’ll start with the simple fixes and then get a degree in electronics!!! I’ll get happy with the copper slip and take it from there.

That sounds a bit weird! You know what I mean…

Ha ha, go easy with that copper slip. I know my post was a bit heavy, I got a bit carried away at 2am.

It is worth checking if the relays are siemens as they are a known cause for problems.
Does the fault happen every time at cruising speed and stall often?

Here’s a start for your electrical studies:


Thanks Haydn,No, it’s not a major problem - just a very brief hesitation at anywhere between 60 and 80 mph, and only at fairly constant speeds - it behaves perfectly when I’m accelerating, but it doesn’t like idling at traffic lights on a warm day after an enthusiastic ride - cutting out quite easily, although it starts again quite happily.It’s more of an irritation than anything else, and I like my bikes to run predictably and without glitches!I’m planning on getting a batch of relays from Pyro Dan as the standard ones are a known weak spot. As long as all goes well, I’ll install them over the winter - it’ll be a good time to get to know the old bird as I’ve never owned a Guzzi before, let alone a bike with FI and only 1 rear shock!As a matter of interest, although the bike is on an 02 plate, it’s insured as a 99 model and the link you gave me for the schematic is for the 99 model - does that make sense?Hugh

Welshguzzi2013-06-12 23:05:44