Odd RPM jump and single beep

Ezgoin

3 times yesterday while idling, my RPMs jumped up for 1-2 seconds, I got a single Beep, then the RPMs dropped back to normal and everyting was fine.  What might be causing that?  (2005 262 Captiva with the 8.1 liter and Bravo 3)

212rowboat

I'd like to tell you it's a simple IAC 'mapping' issue, where the plunger hits a rough spot on the mechanism and hangs up instead of smoothly passing the range it's trying to set, but.... there is a danger here that you ought to consider that could really mess your engine up if left unattended, that in the early stages will behave the same way.

pick up a fuel pressure gauge- the analog kind that screws into your fuel rail via the valve port, and that logs the highest pressure reached during operation... you're looking for ~consistent~ pressure across the entire RPM range and regardless of load... your pump and regulator are 'sposed to maintain a precise pressure to the injectors, else they've no means of adjusting trim accurately...  

hopefully you rule the pump and regulator out- and if so, look at cleaning the IAC with throttle body cleaner... if that checks out, look for a vacuum leak by carefully spraying ether/staring fluid around the intake manifold mating-to-heads-and-block area in very short bursts on a running engine. 

Ezgoin

Good thoughts. Since I bought this boat 6 weeks ago, it's searched for a consistent idle rpm. After a few hours of use it seems to idle a bit smoother, but in gear and just off idle it seems to search and has a slight surge. I've kinda figured it's probably an IAC valve issue since I could find no indication of a vacuum leak. I wonder if the two issues are related.