yamaha s225txrx jumps from 2000 rpm to 3400 rpm without moving the throttle.

TBTech24

Seaman
Joined
May 3, 2011
Messages
56
big jolt almost knocks you down. when increasing rpms to pull out of the whole rpms are steady in the climbing until about 2000rpm. Then it will jump after a couple second pause to 3400 rpm in half a sec. I checked the resistance of the CPS it was within spec on the higher side 228.7. volts where jumping around alot during the test so im kinda leary on the results. spec say at 1500rpm should be 3 volts and 3500rpm 4 volts. well it started out at .60 when i finally got a steady reading from the meter. then at 3500rpm it was 1.9 volts.
TPS read .48 volts with throttle body linkage off on the top butterfly. with it conected it read .64 volts. at wide open throttle it read 3.9 volts. specs say it should be within .48-.52 at idle and 5 i think at wide open throttlle.
engine runs well besides the jolting. im thinking the cps but not feeling the test results cuz of the jumping of the numbers in the meter while water testing the cps and tps. am i good on the cps or does anyone have another thought on the crazy increase in rpms?
 

TBTech24

Seaman
Joined
May 3, 2011
Messages
56
Re: yamaha s225txrx jumps from 2000 rpm to 3400 rpm without moving the throttle.

anyone have any ideas or had this happen to them?
 

frankjohnson

Cadet
Joined
Mar 17, 2015
Messages
17
If yours is an early to mid 90's V76 engine put a timming light on it to see if timming is holding steady. I had this happen on a 95 V76 when the knock sensor started giving bad signals causing my timming to jump from 7 degrees before tdc to 4 degrees after tdc.
 

TBTech24

Seaman
Joined
May 3, 2011
Messages
56
Yes the o2 sensor tested good. I cleaned it and reinstalled. Same problem occurred. I replaced the o2 sensor with the gaskets and problem went away.

Sorry for the late response haven't been on here in a while. thanks for all the help.
Ps when testing the knock sensor and the cps it was funny readings but still within specs.
 
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