300 hpdi idle surge

[muller2357]

have a 2004 300 vmax hpdi
idle surges up and down especially in neutral but also when idling in gear
motor runs great off idle no problems but am worried this idle problem could develop into other problems
i read a lot of posts here with surging hpdis but they all seemed to have issues in the midrange and high rpm areas
this idle only issue has me confused
any ideas are appreciated......not opposed to going to a dealer but just came from one and after they looked at it they said there was a mud dobber nest under the cowl and told me the motor ingested dirt and this dirt is holding a reed open they wanted $500 more dollars to inspect the reeds
i dont know if i believe this and if they are wrong where does that leave me
i'm a gm tech and see guys guessing all the time and wasting customers money
i know for a fact the place i went didnt even connect my motor to yds.....how can you diag an engine performance problem without scanning the ecu

 

[Inducted]

Re: 300 hpdi idle surge

When in neutral the ecu does cut out cylinders. It is quite noticible when running on the hose. Not as much in the water. Malfunctioning O2 sensor will NOT throw a code. The throttle valves must be syncronized properly as well as the TPS, if not it will affect rpm's. Find a dealer with certified tech and YDS. A yamaha manual and a voltmeter and some technical experience and you can synch the throttle valves yourself. Good luck !!!

 

[muller2357]

Re: 300 hpdi idle surge

thanks for the input
i have sync the throttle and the tps today according to the manual and it has gotten way better
wasnt going to do that because that is one of the things i just paid the dealer to d.....did it anyway and it helped quite a bit
you mention an 02 sensor but im not sure this 2004 has one.....or does it?
what does it use to control fuel?
if my tps isn't set just right could it lean out the motor?

 

[Inducted]

Re: 300 hpdi idle surge

Maybe no O2 sensor on that engine. You do want to get your TPS setting correct. The TPS is a primary input for the ecu so is the pulsar coil. The other sensors help with fine tuning. Water temp sensor inputs for cold start enrichment. I'm looking at TPS output voltage at idle 0.58-0.62. I'm not sure if this is accurate for your engine?

 

[muller2357]

Re: 300 hpdi idle surge

yeah inducted .58 to .62 is what my manual said also for tps running at idle
it seems like i have to open the throttle blades too much at idle with the idle speed screw to obtain .60 volts
i have it set at .575 and the surge is very slight over .585 and the surge gets pretty noticeable
im thinking of replacing the tps and readjusting....also trying to see if there is an o2 or not

 

[yamatech43]

Re: 300 hpdi idle surge

There are no o2 sensors on these engines......you have to follow the procedure to set the tps....you can't fudge....the throttle plates have to be SHUT completely. If you can't get the reading....then you can't...replace.