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Poor Fuel Consumption

7K views 19 replies 10 participants last post by  voxmagna 
#1 ·
Well, I'm back with another question.

Some of you may remember that I had a problem getting my 02 RS to run a few weeks ago. So I completely stripped apart every piece of the fuel delivery system, cleaned em, and got the bike running. That was a major accomplishment. :dance:

I've noticed over the last couple of weeks that I have a very strong gas odor when I start the bike, and occasionally when I pull up to a stop. I've also only been getting ~30miles to the gallon, compared to the usual 40mpg that I had before. I've done a complete inspection of the bike when its running, and there are no leaks that I can see.

If the bike is running rich, would that cause extra gas to be expelled through the exhaust?
Maybe a bad O2 sensor causing this?

I firmly believe that these symptoms are inter related.

I've searched through the forum, and haven't found anything that I think matches this.

If anyone knows of a particular thread that address's this, please point me in the right direction.

Thanks again!!!
chris
 
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#3 ·
rasbutan said:
If the bike is running rich, would that cause extra gas to be expelled through the exhaust?
Gun the throttle and look at the exhaust pipe; does a visible cloud of black smoke shoot out? Also sniff the exhaust while the engine is idling; is there a strong raw gas smell?

If you suspect the O2 sensor, this might be of some help.
 
#5 ·
Many things can cause excessive fuel consumption.
1) It could be a leak.
2) High fuel pressure, causes a rich mixture, starting problems, etc. Normally this will cause a lot of black smoke and a black soot to collect on the rear turn signal next to the exhaust.
3) EFI sensors that are incorrect. This includes any sensor that inputs to the ECM to control fuel. O2 sensors are included on that list but have less control over the mixture than many believe. Temperature sensor has LOTS of power over mixture, many times more than O2.

These are but a few ideas. On a car we could connect our handy, inexpensive scan tool and quickly check may of these. Don't have that easy option on your K.

Good luck.

Hans
 
#6 · (Edited)
Check a plug or two first after a warm up and ride of about 5-10 miles. If they are looking black and sooty it sounds like over rich. If the bike has been running very over rich for a while, the O2 sensor may have got blocked up.

Before changing anything else I'd try to find a dealer who will do a 1/2 hour Moditec diagnostic check. It could save you a lot of time and money. The TPS sensor adjustment may be wrong and that will get picked up in the test, as well as the O2 sensor, timing and temperature sensors.

But first make sure you've got no actual leaks and the gas tank filler cap is pushed right down.

I had another thought, does your bike reach it's normal running temperature within about 5 minutes, or is it slow getting there, do the fans ever switch on? I have a vague recollection that an engine temperature sensor is what moves the ECU from rich cold start to a leaner map. Yes there is a thermistor temperature sensor exclusive for the ECU and it's not the one that drives the temperature guage. Sorry I don't know where they put it, but a Moditec test will save you wasting a lot of time.



 
#8 ·
Shouldn't be more than 1/2 hour labor, but say you just want the Moditec diagnostics done and a report - steer them to rich running, TPS,O2 sensor, timing, engine temperature and normal cut-in check for the fans. At least afterwards you might learn if you are chasing a real problem. Ask if you can hang around the bike while the tech is running the diagnostics and you'll learn a bit. They won't need to take any plastic off as the diagnostics connector is under the seat, unless of course you want them to go the next step to adjust or fix. They can also check for ABS faults at the same time.



 
#10 ·
voxmagna said:
Shouldn't be more than 1/2 hour labor, but say you just want the Moditec diagnostics done and a report - steer them to rich running, TPS,O2 sensor, timing, engine temperature and normal cut-in check for the fans. At least afterwards you might learn if you are chasing a real problem. Ask if you can hang around the bike while the tech is running the diagnostics and you'll learn a bit. They won't need to take any plastic off as the diagnostics connector is under the seat, unless of course you want them to go the next step to adjust or fix. They can also check for ABS faults at the same time.

They quoted me between 30 min and an hour based on whats wrong. They also asked me to strip the tupperware....I presume to fix a problem if they find it. I'll RE-ITERATE that I only want the test run. Sometimes the shop manager doesn't quite listen to what I want done. I also set up the time for the end of day on Friday: 1) so I can get in the back and watch, 2) The guys might work a little faster gven the end of the week :thumb:
 
#11 ·
Have that covert videocam on so you can post something on Utube. Would make a change from the usual bike cockpit shots.

Well, if the kiddies can post their phonecam shots of teachers in 'compromising situations' this shouldn't be so bad!

If your problem is TPS adjustment, they'll find this quickn easy and it's much more accurate for them to do it on their machine and wouldn't take long. They'd need access to the throttle body area and for a short ride you could probably just leave 2 or 3 screws in each panel. Make sure before you take the bike in you have plenty of throttle cable slack lock to lock and the slides make a nice click in the shutdown position. Mine hadn't and the first thing they said was 'TPS out of adjust'. Fortunately I was there and remembered I'd foolishly taken out slack when I first got the bike. That was my running rich problem and after I slacked it, their Moditec put the TPS bang in the centre green. Since then I discovered the bike has a small tank, so now I expect the 180-190 mile range to amber low fuel and frequent gas stops - but the seat forces that anyway.

Last thing Friday is a bad time as they'll want to get away quick. Have some chilled beers handy!

It was the best money I spent, Good luck.



 
#13 ·
rasbutan said:
Well, I'm back with another question.

Some of you may remember that I had a problem getting my 02 RS to run a few weeks ago. So I completely stripped apart every piece of the fuel delivery system, cleaned em, and got the bike running. That was a major accomplishment. :dance:

I've noticed over the last couple of weeks that I have a very strong gas odor when I start the bike, and occasionally when I pull up to a stop. I've also only been getting ~30miles to the gallon, compared to the usual 40mpg that I had before. I've done a complete inspection of the bike when its running, and there are no leaks that I can see.

If the bike is running rich, would that cause extra gas to be expelled through the exhaust?
Maybe a bad O2 sensor causing this?

I firmly believe that these symptoms are inter related.

I've searched through the forum, and haven't found anything that I think matches this.

If anyone knows of a particular thread that address's this, please point me in the right direction.

Thanks again!!!
chris
My 04 GT is doing the exact same thing. Huge clouds of black smoke under heavy throttle (more than usual) and puffs every time there is a slight acceleration. After a 2600 mile long weekend the left side case and turn signal are covered in soot and the spark plugs indicate a rich running condition. In addition she doesn't like to idle when cold. The colder the air temp the worse it is. I've swapped out the air temp sensor with no change and I'm leaning towards the coolant temp sensor as the culprit. The O2 sensor is probably also fouled.
 
#14 · (Edited by Moderator)
Well, here I am...freshly back from the dealer. I'll come right out and say it, it wasn't a cheap trip. And if I'm not careful, I may end up on 2007 K12S....damn sexy bike!!

They pulled the bike in and I went in to shoot the breeze with the guys. There was a bit of a commotion about the place as tomorrow is their annual open house. They had the place packed with new bikes!! Damn K12S! :yeah

I spent 45 minutes going from one bike to the next, sitting on and enjoying that new bike smell :yeah

Finally the shop manager came in and gave me the run down. It looked to be the O2 sensor. I've scanned the graphic portion of the output. Take a look at the attached pics.

As was explained to me, a normal output would be a nice shallow sine wave sitting right in the middle of 200 and 650mV. The pic shows the first test run of mine being flat, not great but not horrible. He said after showing me that sheet, if all the tests had come back looking like that...he'd have ruled out the O2 sensor.

During the second run, you can see the sensor start to tank below the 200mV level.

The third run then shows a sine wave, but WAY out of whack(thats a technical term BTW.) At this point, he said they decided to do a fourth run just for good measure.

The fourth run shows the whacky sine wave becoming more eratic.

After showing me these, he said that in order to be absolutely certain it was the O2 sensor that they should replace it, rerun the test. The replace each of the other sensors and rerun the test. Totaling at least 4-6 hours to accomplish this. I took the stack of graphs and decided that I'd take my chance that this was the problem.

So, it cost me $190 for a new O2 sensor, ~$40 for the labor(just to plug in a god damn machine :wtf , this 'hobby' is expensive. :wtf

So, tomorrow morning I'll make an attempt to replace the sensor and report back on my findings. Also, there were some more pages of the report but it was all text regarding the steps if anyone wants to see them.

Let me know what you think.
Chris

BTW...did I mention that K12S is damn sexy?!

EDIT: Pics to follow when I can figure out why they're not posting.
Edit 2: Added pics after getting email - Ray

O2 Test First Run

O2 Test Second Run

O2 test Third Run

O2 Test Fourth Run
 
#15 ·
Make sure the pic's are less than 1Mb in size...

If they're too big and you can't reduce them, send them to me (may have to do it two-three at a time) to razel@k-bikes.com and I'll massage them into view.

By the way, I managed to get a dismal 28MPG going from Big Bend, Texas to Hunt, Texas. Turns out the winds are a lot stronger than they feel. 100 miles and a R1150R was on reserve, and a K1200S was saying it only had 35 more miles left of fuel.
Triple digits may have a factor...



 
#18 ·
When I last checked mine with a 'scope, I seem to remember the stoich mid point sits at 350mV.

The first pic flat lining at about 350mV looks like it was taken soon after starting from cold whilst the sensor was heating up and locked out by the ECU - this would be normal. From there to the last pics, the O2 sensor is shown switching either side of the 350mV stoich but you should be seeing a flat top square waves at the upper and lower limits. I think they are incorrect to tell you it should be a sinewave. The sensor is in a high impedance amplifier loop with lots of voltage gain. When the sensor loses sensitivity the max/min peaks will round off - perhaps they see this most often, but my fresh new sensor was showing flat like the books said it should.

The next clue to low sensor sensitivity is the rise and fall edges moving to max and min. These should be as near vertical as possible not rising gently and sloped. One thing I couldn't work out in the pics from the time axis, was the rate at which the switching was taking place. I have a vague recollection of several times per second being good.

The new sensor should look different, hope it works better for you. My Bosch universal non-oem sensor got rid of the soot on the muffler and I got 2-3mpg improvement.

Did you get any readings back from the engine temperature sensors?



 
#19 ·
voxmagna said:
When I last checked mine with a 'scope, I seem to remember the stoich mid point sits at 350mV.

The first pic flat lining at about 350mV looks like it was taken soon after starting from cold whilst the sensor was heating up and locked out by the ECU - this would be normal. From there to the last pics, the O2 sensor is shown switching either side of the 350mV stoich but you should be seeing a flat top square waves at the upper and lower limits. I think they are incorrect to tell you it should be a sinewave. The sensor is in a high impedance amplifier loop with lots of voltage gain. When the sensor loses sensitivity the max/min peaks will round off - perhaps they see this most often, but my fresh new sensor was showing flat like the books said it should.

The next clue to low sensor sensitivity is the rise and fall edges moving to max and min. These should be as near vertical as possible not rising gently and sloped. One thing I couldn't work out in the pics from the time axis, was the rate at which the switching was taking place. I have a vague recollection of several times per second being good.

The new sensor should look different, hope it works better for you. My Bosch universal non-oem sensor got rid of the soot on the muffler and I got 2-3mpg improvement.

Did you get any readings back from the engine temperature sensors?
I don't think I did, but I'll look through the paperwork again.

When I pulled the old unit, the tip was white. Any ideas why? I would've thought it would be black.
 
#20 ·
That far back near the manifold is the hottest part. It's when the gases get further through the muffler and cool that you start to see the unburned carbon deposits. There's been various posts suggesting when O2 sensors should be changed. Unless its been poisoned, it should go for 30K miles easy. I'd change then and at least that should be one less part in the ECU to think about.

You don't come across them much these days, but I still have a Colortune kit with all the thread adaptors. I like it for peeking inside to get a bit more info and to persuade me if a motor is running rich or lean. I tried it in my KRS on startup (when the O2 sensor is flat lining) and the combustion flame was yellowish. By the time the fans cut in and the motor was up to temperature the combustion was running blue. So I concluded changing the O2 sensor a success and went riding. Whilst looking at the O2 sensor output I did some other experiments with propane gas to unbalance the loop and move the stoich towards rich whilst watching for correction, but that's for experts with a fire extinguisher handy.



 
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