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Discussion Starter · #1 ·
i have a 03 600. I have had issues with it since i bought and this is the last thing to fix. For some reason the throttle bodies are not operating correctly. when you turn the key on they are supposed go from fully closed to fully open to half open. Mine go full closed, full open, full closed. checked the secondary throttle switch, replaced wire harrness, synched throttle bodies, replaced ecm. At 3/4 throttle bike runs perfect then if you open throttle wide open at any rpm it has a horrible flat spot. the fuel is getting cut out and i have no clue what is causing this. any ideas?
 

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Have you tried adjusting the stps? It's similar to adjusting the tps except you need to use a multimeter instead of the lines on the cluster.

Check the tps while your at it and see if that solves your problems.:thumbup:
 

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Discussion Starter · #8 ·
if you mean the butterfly valves on the throttle body then they do. They act wierd though.
when you turn the key on they are supposed to go from 1.fully closed 2.fully open 3. half open
mine go 1. fully closed 2. fully open 3. fully closed. im not sure what is causing the butterfly valves to operate like this
 

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Did you follow the proper procedure for syncing the tb's? If you adjusted anything incorrectly it'll leave your tps out of whack and since the stva reacts to tps input, it'll jack your whole setup.

If your sure that everything is correctly sync'd and adjusted (idle, tps and stps) then like Tee said, you probably have either a malfunctioning stva or stcu. Both of which will store a code in the cluster.

I'd love to help you out, get back with more info and we'll go from there.:thumbup:
 

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Discussion Starter · #11 ·
the throttle bodies are synched almost dead nuts. tps is just above the middle line. I am guessing a little so i bought the sensor thats in the tail (in pic). the one i have does nothing when i disconnect it, the bike acts the same. Do you know exactly what this sensor/computer does? how do you adjust the stva?
 

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How did you set the secondary throttle position sensor? What were your full open/ full closed values?

They should be-
open=4.0v
closed=0.8v

My guess is your stps is off and its fooling the ecu into thinking that its half open when it's really closed. Does that make sense?

Also make sure that after you make your adjustments and tighten down the two set screws that your values remain the same. Sometimes the sensor will move a bit while tightening the screws.
 

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Discussion Starter · #13 ·
okay that makes sense now. My dad tested that sensor with a meter and using the repair manuel for refrence. The readings were all within the specs. would it matter if they werent exactly what you stated. also we tested it with bike on but not running. then closed the valve manually and took a reading. then opened it fully took another reading. Is this the right way to test it?
 

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Discussion Starter · #14 ·
okay that makes sense now. My dad tested that sensor with a meter and using the repair manuel for refrence. The readings were all within the specs. would it matter if they werent exactly what you stated. also we tested it with bike on but not running. then closed the valve manually and took a reading. then opened it fully took another reading. Is this the right way to test it?
 

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You want to get it pretty much dead on but a little off (like 0.1v or less) isn't going to cause the problem your discribing.

When you had the meter hooked up did you watch the meter while you moved it from closed to open? It should ramp up evenly and smoothly. If the voltage jumps from like 0.8v to 2v to 4v then the sensor is worn out. It should rise/fall in 0.1v increments.

What have you replaced so far? You mentioned the ecu and the stcu, anything else?
 

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Discussion Starter · #16 ·
the wiring harrness was cut up so replaced that. coils, ecm, thermostat and i bought throttle body control unit that goes in the rear tail. However the previous owner had replaced this part. im just thinking maybe the havcked up wiring harrness caused this to blow. When i remove it the bike acts the same.
 

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Ok, thats the stcu. If you've got the shop manual there is a procedure to test it.

The tps sends a signal to the ecu and then the ecu sends a signal to the stcu telling it to open or close the stva. The stcu sends a signal to the stva and the stva position is read by the stps and relayed back to the ecu.


Check to make sure the ecu and stcu are communicating with each other.

Were you able to check for any codes by jumping the dealer switch in the trunk? That would be a great help in pinpointing your dilemma.
 

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Discussion Starter · #19 ·
did you mean resitance or voltage? and how do you get a voltage reading? do you back probe the connectors with the ignition on? also do you know the procedure to adjust the stv sensor i cant find it in the manual? when you do the test on the stcu do you do it with the ignition on back probing the connector?
 

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You can test the stp using resistance. 0.8k-3.9k ohms closed/open.

To check for power to it from the stcu, back probe the yellow and black wires and read voltage from 0.8v-4.0v with key on.

If you've replaced the ecu and the stcu already and your still having problems, all that's left is the stva and the stps or faulty wiring.

The stcu is wired directly to the ecu, follow the wires and check for damage. Do the same for the actuator/stps lead.
 
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