Motorcycle Repair: Suzuki Boulevard C-50 2006, sophisticated test equipment, computer controlled systems

Question
QUESTION: This fuel injected 2006 Suzuki Boulevard C-50 intermittently surges and bucks at low throttle setting, just off idle.
It seems to be most prevalent at low speeds and in lower gears. (20-30 MPH 1st, 2nd and 3rd gear)

This has happened since new, with or without an aftermarket tach hooked up and at all engine temperatures. It seems to happen more often in warm dry ambient conditions. When driving in traffic at 20-30 MPH just as the slack is taken out of the throttle cables the engine surges as if the fuel is being turned off and on.


ANSWER: Steve,

this is most likely due to a lean
fuel mixture. Newer fuel injected bikes
seem to be set very lean to pass emissions
and import standards. The only
solution is to have them dyno tested
and remapped with something like
the power commander device:
http://www.powercommander.com/powercommander_iii_usb/powercommander_all_download
Tinkering with the fuel injection is out of the hands of the
backyard mechanic for the most part.
Computer controlled systems need more sophisticated test
equipment to keep them in shape.
Sorry I can't suggest much else,
you could check for loose or bad computer unit
connectors and loose battery cables or ground wires.
Sometimes a loose connection or bad grounds
can cause ignition problems.
.


---------- FOLLOW-UP ----------

QUESTION: Thank you for your quick response. I was called away for awhile but made it home for Thanksgiving. It was 56 degrees and the bike ran great. I know once it gets to 70-80 degrees it will start surging and bucking again. What I don’t understand is why no one else seems to be having this problem. I live and drive in Massachusetts and New Hampshire where it doesn’t get extremely hot in comparison to Florida, the Mid-West or other parts of the country. I’ve not seen on any other web site where anyone has experienced this problem.
1. Would this be something in the dealer set up or the import set up?
2. Does a dealer have a dynamometer or is that a specialty shop?
3. I thought fuel injection eliminated problems with temperature and altitude?

Any and all help in understanding this would be greatly appreciated.

Thanks


ANSWER: Steve,

the fuel injection is amazing but a much more
complicated fuel system electronically.

-It may have been working perfectly when new
but now has a small glitch somewhere.
A good dealer can hook the bike up
to a device that checks for trouble codes
and possibly it can diagnose the problem
component without trying to change things
without knowing what the problem is and
wasting money.

-Some bigger dealers also have dynometers that
can check the bikes performance from
slow to top speed and help to indicate
what needs to be done. There may be other
shops that can do this also.

-Fuel injection takes information from these
sensors:
-engine coolant temperature sensor
-crankshaft position sensor
-speed sensor
-atmospheric pressure sensor
-camshaft position sensor
-intake air pressure sensor
-intake air temperature sensor
-throttle position sensor,

it sends all this information to the electronic
control module or computer where it
sorts it out and then adjusts the fuel system
and ignition timing accordingly.

-This can make a great running engine
unless some sensor fails or connector comes
loose. As you can see it needs to be
checked for error or trouble codes
by a qualified dealer because of
all the sensors involved.

-The computer ECM is under the seat,
sometimes just checking it's
connector might help,
it can be as simple as a loose wire or
battery cable or as complex as the many
sensors make it. Very good system when working,
a pain when it's not unfortunately.





---------- FOLLOW-UP ----------

QUESTION: Thanks

I’ve had three dealerships check the codes, check the connections and two of them checked the throttle position sensor. They all stated there are no hidden codes and everything checked fine. I had one mechanic try blocking, balancing and then disconnecting the PAIR system. That didn’t work either. Suzuki won’t do anything until a dealership duplicates the problem. Suzuki won’t honor warranty past one year even though I’ve reported it several times. I’m afraid I’m going to be stuck with this problem in the spring on my own. I took it out again for about 100 miles and it ran perfectly. The ambient temperature was 42 degrees. I really believe it’s tied to ambient temperature at that particular throttle setting (just off idle). Suzuki stated not to ride at that setting. In the heat of summer you can feel it surge and buck as you go through that setting. All temperature senders were checked by the last dealership and tested fine. Two of the dealers stated they can’t get inside to change the mapping.
Could this one have been set too lean?
Both dealers wouldn’t check it for me and I no longer trust the third dealership. Is it difficult to check?

Thanks for your help.


Answer
Steve,

it is odd that no error codes show but
maybe the problem is come and go.

-I personally suspect either a sensor
or the way Suzuki protects the fuel
from excess heat.

-When the engine coolant temperature is hot
say around 225F degrees,
the control module or computer increases
the fuel by 15% to cool the fuel.
This may be the surging you feel as the
fuel injection increases it's delivery.

-This is just a result of design and
can only be affected by a remapping device
like the "Power Commander" I mentioned before.

-If you make sure your bike has a good
thermostat or cooler thermostat
and bleed the cooling system of any air
pockets, it may help to keep the bike
from changing to it's hot engine fuel mapping.

-this also would explain why it only happens
in warmer weather.