2003 DT225 running bad at idle

[seaox230c]

Just launched for this year and can't keep it going at idle...it will run rough for a few seconds or a minute then dies. I am running new clean fuel off an aux tank...I have verified good fuel pressure at the rail of 37-39 psi at all times. I have found that my timing is off at +10 degrees which I assume to be 10 deg AFTER tdc...its not marked on the wheel but I know which way it rotates and it shows 30-20-20 T 10 ...rotating towards the left. I have the factory manual and it is not too much help as usual. The plugs are not misfiring...just the timing is off. I get no failure warnings on the multi function gauge. I thought I had it narrowed down to the port cyl temp sensor which varies timing according to temp...when I pulled it out of the block...it ran good for 3 or 4 minutes at 3 ATDC which is correct but I cant get it there again...[I] replaced it and same result...+10 deg after the 3 sec startup...if I disconnect it it goes to failsafe -10Deg btdc but the idle is way high. I have verified the TPS rigging num times and all textbook numbers. It stays at +10 deg even if I push the throttle up which is a mystery. I have checked the resistances of the sensor at numerous different temp and they are all ballpark...shouldn't change the timing by that much

[Solarman]

Check the gear count coil & its distance, and condition. Also, check wire connections and condition of wires from port sensor and around magneto.

Good luck. Let us know when able.

[seaox230c]

Have I mentioned Suzuki's are impossible to work on....The port temp sensor is a dual combination sensor...one half the green to black is the cyl wall temp sensor and it should read a few thousand ohms when cold and approx. 500 when at operating temp...the other half feeds the ecu and is the violet and black wire. The cyl wall temp sensor basically matches the charts in the book at various temps....the other half..violet/black has NO mention in any section of the factory manual. It starts off around 40K when cold and drops to around 10k when warm.I have no written reference for this. When I disconnect or short the green to black...nothing happens. no change in rpm...no change in timing...no faults on the monitor. I substituted a decade box for the cyl wall temp sensor...when it goes below 380 ohm the timing is supposed to go to failsafe 10deg btdc...nothing. If I hook up the cyl wall temp sensor and disconnect the violet wire the timing goes to failsafe 10 deg btdc. If I hook the violet wire back up and the sensor is hanging on the side of the block-cool- the timing is perfect at 3 deg atdc as per the sticker on the engine cover but the idle is a few hundred high because it senses cold operating temps. If I put it in its proper holder within 30 sec the idle drops pretty low and the timing goes to 10 deg atdc and it sputters and backfires. I know the tstats are working because they are brand new and I can put my hands on both cyl heads...very warm /almost hot but not enough to burn or cause pain. Like I said...the factory manual makes no reference at all to the 2nd half of the port sensor...only the cyl wall side and that appears to have no effect on engine operation but it should according to the manual

[Solarman]

Does the starboard cylinder sensor on your motor also have 4 wires, and what do they read? Same colors?

Post back when able.

[seaox230c]

No the right bank has a round overheat sensor with only a green/red and black wire...it appears to be a dedicated overheat...when I trick it it sends an overheat signal to the monitor . I have only tricked it a idle so I don't know if it would limit the rpm to 3000 but it does illuminate the temp light and warning horn. I can find no written value for that signal just trial and error with the decade box... I gave some mis-information yesterday...I was doing all the work on the engine and didn't hear any warnings from the monitor gauge so I assumed no faults....I disconnected the green and white wire -cyl temp sender and I got the check engine light flashing 1-4...no warning horn. Then I dialed in lower resistances from 1000 down to around 50 once the green was hooked up to anything...no check engine light and no change in any other parameter...the timing is supposed to go failsafe 10 deg btdc at anything below 350-380...nothing stays steady at approx. 3 deg atdc for all values from 10000 down to 0...system is not working the way the manual says...but manuals have been written wrong before...its running nice with the sensor just hanging next to the block but I don't like leaving the left bank without any overheat protection and I'm sure im loosing some efficiency due to not compensation for cyl temp but if I reinstall it it runs like crap...probably going to get a new sensor and see how that works out

[Solarman]

If you're certain it is all related to the sensor, then go for it. I have seen many thermistors lose calibration, or sensitivity to temperatures during operations.

Good luck. Post back how it works.

[seaox230c]

problem is im not sure its related to the sensor...the manuals make no reference to the non-cyl wall side of the sensor and if I adjust the cyl wall sensor to simulate various temp...the system does not respond as written...The idle is now extremely smooth with the sensor just left hanging...better than ever but I don't know how that affects the engine at high speeds...it seems ok compared to prev outings.emp sensor and I should be able to manipulate the timing based upon temp changes of the cyl . I cant check the timing at speed until I get a second person to drive