Mysteriously bad fuel economy

[bixxer bob]

That persisting lean 0.04v value explains why its trimmed itself rich. Air is getying in somewhere when it's not supposed to; now you just have to find the leak.

[Aryeh56]

Well lads, its been more fiddling and guessing and not really any signs of improvement. I had an odd thing happen last week, though. There was a broken wire on my bike, a Black and white one which runs from the front brake to the brake light fuse. I had fixed it with solder a while back, but the solder came undone last friday and left me without a tail light. I'm delivery driving these days, and it was the middle of a shift, so I ran to the autopart store and got some crimp-on connectors and a cheap pair of pliers. When I fixed this cable which isn't even for the actual brake system, let alone engine managment, the bike started purring like a happy kitty again. I have not felt it run that smooth since these troubles started. I've spent hours pouring over the whole circuit diagram and I've got no explanation at all. It's bullsh*t. Doesn't make any sense.

Moreover, even though its running silky smooth again, it's still getting stupid bad gas mileage. I've done a mix of city and highway riding and I'm getting around 31.5 mpg. The rough running also briefly re-appeared yesterday...even though my brake light still works. (Boy, that's a weird sentence!) Since I'm entirely out of guesses I took the advice of a buddy of mine whose an auto-mechanic. I finally spit up the cash for an infrared thermometer so I could check temps on the exhaust headers. Sure enough, cylinder two is reading 20-50 degrees colder than the other two in a variety of running conditions. It also takes significantly longer to heat up than 1 & 3. Based on finding this, I'm gonna check Bob's suggestion about the secondary air injection again in more detail. I'm gonna rent a bench at the local shop so I can do this indoors, which means I can get deeper into the system than I was willing to before.

If it's not the air injection, what are some other likely culprits? Could the injector have gone? Something with spark or ignition? Once again I'd appreciate any advice you guys have. You've all been awesome thus far.

[CaptainTrips]

Is it as simple as the center cylinder is not firing? I would pull the spark plug and have a look at it. Also, check the rubber intake boots for cracks and fitment that would throw off the fueling computer.

[bixxer bob]

A point I forgot to include, the air valve in the airbox could also be faulty.  If you have Dealer Tool  software there's a test for it .  Running the test simply opens ans closes it a couple of times.

[eddieb]

Originally Posted by bixxer bob

I had a, period where my 2013 model had adapted itself rich and fuel consumption was high. It turned out to be an air leak on the air injection system.
How it works is this... In order to meet emission targets, air bleeds from the air box, through a valve to reed valves in the cam cover. From there the air follows two galleries through the cylinder head and into the exhaust where it transfers into the header pipes. Injecting air here burns residual fuel in the exhaust thus cleaning the emissions but also causing exhaust popping. The difficulty here is the ECU  monitors the exhaust mixture via the O2 sensor in certain circumstances and trims the mixture either rich or lean depending on what the O2 reads. Bleeding air into the exhaust will cause a false reading (lean) and the ECU will richen the mix. To prevent that happening, as the ECU reads the O2 sensor it closes the airbox valve thus shutting off the bleed air.

Having understood that, its easy to see that any air leak downstream of the valve is going to cause a rich mixture eventually. In my case it was a web from the gasket for the three plug holes that had become trapped in an air gallery after a valve clearance check and preventing a good seal.  Took some finding though

Hi, this (air leak in the air injection system) sounds like the cause of the problem I'm experiencing! My bike went to a local dealer for a valve clearance adjustment service and came back running very rich and with terrible fuel consumption right afterwards. I've had the bike for 6 years / 80000km with consistent fuel consumption over this period (depending on riding style), so raised it with the dealer: The dealer rechecked everything and informed me that nothing was amiss and that the fuel consumption I now see (about 12km/l) is normal (although I consistently averaged around 17.5km/l the past few years).

I’ve rebuilt motors and gearboxes on other (simpler) bikes before (I am a hobbyist mechanic), but have not worked on my Triumph before: Is the gasket you refer to the one for the 3 plugs that fit underneath the CAM cover (see here )? Any advice on how to spot and fix this?

To try to identify and resolve the source of the fuel consumption issue so far, I’ve replaced the plugs and air filter, ran injector cleaner through the system a few times (I know this is not always effective), tested the O2 sensor, made sure there is no friction (e.g. stuck brakes) and did the 12 min reset – all with no difference to the bike’s fuel consumption.

I also checked the header temps with a thermal reader when running the bike:  the readings were all over the place when idling, with up to 30-degree difference between min and max reading at about the same time, and no clear warmer or colder header (the warmer/colder headers would alternate over time). At higher revs (3500rpm), the no 1 header is consistently running about 80 degrees colder. It could be an injector-related issue, but all 3 new plugs are pitch black from running rich (after only 600km), so I suspect running very rich is the ultimate cause of the temp differences (maybe the plug is not sparking properly due to carbon build-up). 

Any thoughts on what else I can check / other lessons learned around sudden fuel consumption issues?

[NiK]

Gasket between engine and exhaust?
I had it replaced on my Tiger 1050 some years ago. AFAIR a kind of ticking noise coming from the frontend alerted me.

[bixxer bob]

Given that it started after the service, it must be something that was disturbed during the service.
If the valve clearances were done, then a problem similar to mine is a good shout.
The cold running on one plug suggests that one isn't firing properly so may be soot build up, but also may be a problem at the coil stick plug.
Any which way, you'll need the tank off for a look-see.
Before you do that, you could do a couple of ECU adaptations and see if that helps. It probably won't but it's worth a go.

Adaption is done automatically when following conditions are met:
Gearbox in neutral , clutch engaged.
Coolant temperature 80 - 100 degrees Celsius.
Airbox temperature min 21 degrees Celsius.
Engine idling for 10- 30 seconds.

To force adaption:
Start engine and warm it up until above conditions are set.... adaptation will then take place automatically.
Blip the throttle every 30 sec to start another adaption cycle.

[eddieb]

Originally Posted by NiK

Gasket between engine and exhaust?
I had it replaced on my Tiger 1050 some years ago. AFAIR a kind of ticking noise coming from the frontend alerted me.

Thank you for the feedback Nik – I’ll have a look!

[eddieb]

Originally Posted by bixxer bob

Given that it started after the service, it must be something that was disturbed during the service.
If the valve clearances were done, then a problem similar to mine is a good shout.
The cold running on one plug suggests that one isn't firing properly so may be soot build up, but also may be a problem at the coil stick plug.
Any which way, you'll need the tank off for a look-see.
Before you do that, you could do a couple of ECU adaptations and see if that helps. It probably won't but it's worth a go.

Adaption is done automatically when following conditions are met:
Gearbox in neutral , clutch engaged.
Coolant temperature 80 - 100 degrees Celsius.
Airbox temperature min 21 degrees Celsius.
Engine idling for 10- 30 seconds.

To force adaption:
Start engine and warm it up until above conditions are set.... adaptation will then take place automatically.
Blip the throttle every 30 sec to start another adaption cycle.

Thank you for all the great pointers Bixxer Bob – I’ll work through the list and hopefully get to the bottom of the issue soon!