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Penta 5.7 GSI idle issue

Maverick944

New member
Volvo Penta 5.7 GSI- pls help! Having an idling issue and very open to advise... my engine idle bounces in a manner very similar to a sticking IAC.... when I start the engine it bounces. It will intermittently smooth out and then start bouncing again for no obvious reason. Putting it under load and then shifting to neutral can result in the idle bouncing or it might smooth out... the symptom does not change whether the engine is warm or cold... runs great off idle and isn’t lacking any performance when under way...


Before this season began, the dealer replaced the transom seal. The motor was out. Last season is was smooth as glass. Could be coincidental... so far the marina has sent the freeze frame data to the local volvo rep and they don’t see any sensors or values out of normal. They’ve been throwing parts at it since. So far they have checked for vacuum leaks, replaced the MAP sensor, fuel pump, ignition coil, cap, rotor, wires, throttle body (new iac and TPS included), injectors were also replaced. also, the idle continues to bounce with the IAC disconnected and also bounces with the TP sensor disconnected. Base timing is also correct.


The symptom remains. No fault codes are being set.


Does this setup have the equivalent to a park/neutral switch that would be found in a car? I’ve heard TBI 350’s had similar symptoms when the park neutral switch was bad... it’s supposed to vary the idle based off whether the engine is in gear or neutral....


We’re running out of ideas... thoughts and advise are welcome!
 
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