200HPDI unstable idle

[arkansasboatman]

Hello all<br />I have a 2002 200HPDI that has an unstable idle. This condition started after replacing the power head. Have replaced seven other 200HPDI power heads with no problem. The engine starts and runs fine at all speeds and does not die at idle. <br /><br />Problem; for no aparant reason the engine will gradually increase idle to about 1500 rpm then fall back to 700-800 rpm. Watching the laptop while running YDS, the timing appears to be leading the RPM increase. The timing increases also during the increase of rpm. This will happen during the entire time the engine runs. I have varified all of the sensors, changed the injectors, changed the thermo sensor, replaced the connector for the thermo sensor with Yamaha bullet connectors to make sure I was getting a good signal from the thermo sensor. The O2 sensor housing has been cleaned and O2 sensor changed. All of the settings displayed in YDS are normal. There are no fault codes. During the power head change the throttle body and reed valve assemblies were thoroughly inspected,cleaned and torqued at assembly. Throttle valves were syncronized and TPS set. All new gaskets were used. I have spent many hours working on this problem and am stumped. Any help will be appreciated.

 

[mrn714]

Re: 200HPDI unstable idle

Have you attempts to blow all vacume / fuel lines. It sounds like a air / fule problem to me, but without the print out, can not be sure. Just a thought. Others will add.

 

[rodbolt]

Re: 200HPDI unstable idle

hello<br /> the laptop wont help. if the timing is changing it has to be told to do so by the TPS or the CPS. howerver certain failures will fix the timing at 7BTDC. are there any codes set? are all the orange wire 5 volt signals correct? remember the 5 volt reference comes fro 2 places on the ECU. what is the air gap on the CPS?it sounds like the timing is going between fixed at 7 BTDC and normal control. what is the injector pulse width doing as the speed increases? if the pulsewidth is lengthening then I would look very closely at the O2 sener and the TPS.if the timing is climping to 7*BTDC look for a sensor wire that is incorrect.<br /> do you have a list of the sensor failure codes and what affect it has on the engine?<br /> good luck and keep posting

 

[arkansasboatman]

Re: 200HPDI unstable idle

Thank you for the suggestions. I have all of the info on the sensors, failure codes and function. The voltage output of the TPS is not changing. I will have to recheck the air gap on the CPS. The best I can remember the 5 volt reference voltage is a little low. Can't remember the injector pulse width during RPM change. You have presented a lot of issues that I have missed. It looks like I need to hit the books to solve this one.

 

[rodbolt]

Re: 200HPDI unstable idle

hello<br /> I have a 200 HPDI here that runs about 4.7 on the ref voltage, its that way out of the ECU but so far no running problems. if the timing is going to 7* BTDC then there is a list of causes.<br />ign timing has 2 main determinants and one corrective the mains are TPS and pulser coil signal. the temp sensor is used as a corrective thing for warm up.watch the fuel pulse width when it surges. if no trouble codes are set then its not a malfunction of a part but a misoperation. the computer cant tell if a plug or ign coil failed. it just monitors whether or not the signal was sent to fire it.<br /> its been my observation that the laptop is not much good as a trouble shooting tool other then to tell me quickly what aint broke. usually if something actually breaks its easy to find.<br /> good luck and keep posting<br />there is a sensor failsafe function chart that may help or take readings and post them back