Logo
FULL SITE MENU

Idle surge gt-40 EFI

M

mark12

New member
Does anyone have any info for an idle surge problem on 1996 PCM Gt-40 EFI engine.Boat has new plugs,fuel filter/separator,new fuel pump and runs great off of idle but surges approx between 500-800 rpm's when at idle.Is there a idle controller or does the control module the only control for the idle?
 
Just for an update or anyone else who experiences this same problem.The problem in my case was the IAC (idle air controller) which is located on the throttle body(back of engine along with the throttle position sensor(top of engine plenum).The PCM EFI manual is difficult to understand much less help troubleshoot.Using an ohmmeter to check the resistance of the solenoid is redundant as the book shows,here is the best way to troubleshoot if you know how to use a multimeter.First check for voltage (key on engine off) on either wire at the IAC soleniod and using the cover plate bracket as your ground.As long as you have voltage on either wire the (ECM)control module is fine.Remove the IAC and spray carb cleaner on plunger from the backside.Let sit for a minute then blow out excess with compressed air or suck out with shop vac then shake to make sure all carb spray is gone.Do not leave carb spray in and install it will eat up plastic components/plunger inside.Start engine up with IAC connected gently tap on the outside with a plastic mallet or screwdriver handle,then disconnect while running for about 20 seconds engine will be real erratic and reconnect it should smooth out if valve is repairable.If valve does not free up sadly you will have to replace it to the tune of $200 plus.Please note you must check for vacuum leaks first/make sure you have a new fuel filter/adequate fuel pump pressure and are experiencing no other problems.The way to tell if this problem is to move engine off idle out of gear to approx 900-1000 Rpms and if it runs smooth this is possibly your problem.This is only a rolling idle/surging idle problem not a driveability issue.If you have other symptoms refer to PCM EFI diagnostic manual and check all the things they list for matching symptoms.I have the manual(GT-40 Pro boss only) if anyone needs assistance e-mail me at [email protected]
 
Back
Top