help.....got some sort of a dull alarm sound in the car before the idle speed jumps up 200 revs then back down....any idea

 

What?? Could you describe the problem you are experiencing a little better? What are you working on (year, engine, drivetrain)?

 

Theory 1: Previous own did a diesel engine swap, the alarm is the glow plugs priming the cylinders before ignition.

Theory 2: Its the engine bogging down as the rpms are too low, the idle jumps 200 rpm to normal range, 'dull alarm' goes away.

Theory 3: ????

Theory 4: Profit