Excessive Engine Braking - Not TPS!

[Reclaimer033]

I need some help. I don't know what to check next. About 5 weeks ago my bike started engine braking more than normal. Before, it would coast fairly well. After this started, I would let off the throttle and would end up way too close to the tank. I started searching the sites for answers. I tried adjusting the idle screw. That worked for about a day. Then it developed the dreaded TPS symptoms, idling around 500 rpm, stalling out when down shifting, fuel mileage around 30 mpg. I checked and the sensor had not been replaced. I got the sensor replaced and those symptoms went away, but the engine braking is still there. It would be such a big issue to me if it wasn't intermittent. It usually doesn't start doing it until about 5 - 7 minutes into a ride. I commute 30 minutes one way on city streets. It will start doing it, then three or four stops later, it won't. The two or three stops after that, it will start again. My fuel mileage is still down around 40 mpg. I used to get 48 - 50 mpg before this all started. I've changed plugs, and the air filter. Pulled off the exhaust and cat to make sure nothing was plugged up. (they are back on now) I have no aftermarket performance parts on the bike. It's stock except for my GIVI case on the back. Please help. What's next? Tear into the tranny? Oh, yeah: 2004, silver, 19,000 miles.

 

[tuningfork]

1. maybe you need to sync the throttle butterflies in conjunction with setting the idle speed and tps?

2. brakes dragging?

3. check the inlet air temp sensor, pressure sensor, and coolant sensor...all are used for air-fuel settings which could affect your mpg and overall operation.

 

[wrightme43]

New means New it does not mean good.
The new TPS may be bad.

 

[Reclaimer033]

1. maybe you need to sync the throttle butterflies in conjunction with setting the idle speed and tps?

2. brakes dragging?

3. check the inlet air temp sensor, pressure sensor, and coolant sensor...all are used for air-fuel settings which could affect your mpg and overall operation.

I haven't synced the throttle bodies yet.
I've done the onboard diagnostics checks of the sensors, but I haven't checked the actual resistance of the sensors. I will try to get to that this weekend.
The brakes squeak, but they don't drag.

 

[Reclaimer033]

New means New it does not mean good.
The new TPS may be bad.

I've checked the onboard diagnostics (15 - 101) but not the actual resistance. Looks like I'll be busy with the multimeter this weekend. If it is still bad, I would think it will be much harder to replace a second time for free.

 

[wrightme43]

Well if they put a bad part on its not your fault.

 

[tuningfork]

Following the diag tables in the manual for the FI system, they suggest to also check the air injection system.

The fact that it is cyclical seems to indicate the coolant temperature may have an affect...the air-injection does monitor coolant temps.


Here's some snips from the manual:

page 7-6 (what to check if operation is not normal AND the check engine light is not on: )

Check the operation of following sensors and actuators
in the diagnostic mode (Refer to “Diagnostic
mode table” in chapter 7.)
01: Throttle position sensor (throttle angle)
30: Ignition coil #1, #4
31: Ignition coil #2, #3
36: Injector #1, #4
37: Injector #2, #3
48: Al system solenoid





Page 7-32 in the 2004 manual.
AIR INDUCTION SYSTEM
AIR INJECTION
The air induction system burns unburned exhaust
gases by injecting fresh air (secondary
air) into the exhaust port, reducing the emission
of hydrocarbons.
When there is negative pressure at the exhaust
port, the reed valve opens, allowing secondary
air to flow into the exhaust port. The required
temperature for burning the unburned exhaust
gases is approximately 600 to 700C (1112 to
1292F).


AIR CUT-OFF VALVE
The air cut-off valve is controlled by the signals
from the ECU in accordance with the combustion
conditions. Ordinarily, the air cut-off valve
opens to allow the air to flow during idle and
closes to cut-off the flow when the motorcycle is
being driven. However, if the coolant temperature
is below the specified value, the air cut-off
valve remains open and allows the air to flow
into the exhaust pipe until the temperature becomes
higher than the specified value.

 

[tuningfork]

more diags page 9-2:

INCORRECT ENGINE IDLING SPEED
ENGINE
Cylinder(s) and cylinder head(s)
- Incorrect valve clearance
- Damaged valve train components
Air filter
- Clogged air filter element
FUEL SYSTEM
Throttle body(-ies)
- Damaged or loose throttle body joint
- Improperly synchronized throttle bodies
- Improperly adjusted engine idling speed
(throttle stop screw)
- Improper throttle cable free play
- Flooded throttle body
- Faulty air induction system

ELECTRICAL SYSTEMS
Battery
- Discharged battery
- Faulty battery
Spark plug(s)
- Incorrect spark plug gap
- Incorrect spark plug heat range
- Fouled spark plug
-Worn or damaged electrode
-Worn or damaged insulator
- Faulty spark plug cap
Ignition coil(s)
- Broken or shorted primary or secondary
coils
- Faulty spark plug lead
- Cracked or broken ignition coil
Ignition system
-Faulty ECU
- Faulty crankshaft position sensor

 

[Reclaimer033]

I have a copy of the owner's manual and the service manual. I guess I will start in on the air induction system too. I'll keep you guys posted. Does anyone need any pictures of any particular part since I will be disassembling my bike once again?

 

[interactive3]

I don't know about the MPG and engine performance issues, but I can tell you that my 2006 has a substantial amount of engine braking if I'm not on the throttle. The intermittent thing is unusual. Keep us posted.

 

[Denver_FZ6]

Can you relate the amount of engine braking to the idle speed? My thought is your idle speed is varying, it will directly relate to how much drag the engine produces.

During initial startup, the system keeps the idle high to warm the engine up quickly, during this time you wouldn't get as much engine braking. Once operating temp is reached, the system reduces idle speed to normal, and you would then experience more engine braking.

Short of something catostrophic like cracked head or burned valves (unlikely), I can't see anything inside the motor that would vary the amount of braking it produces. More likely vacuum leak or fuel delivery issue.

 

[tuningfork]

how did you make out?