how do I increase idle speed on GT 40

[eseybold]

have 2000 SNOB gt40 EFI - runs great - all tuned up, new fuel pumps, filter, plugs, cap,, wires rotor etc- we ski everyday and it runs great all day but the idle is too low in gear( 580 -600rpm, supposed to be 650) and sometimes it is hard to start when hot .....sounds starved of gas when it is cranking.......if I start with a little throttle it will start....or maybe not...if I let it sit it will start. Does not run hot.
........................do I simply tighten the idle control screw on the engine until baseline rpms go up or should I look to replace my TPS,MAP sensors etc. Good fuel pressure(35psi) at the FCC. Could it be a fuel sensor relay going bad? I already bought a spare relay but have not installed it. Ethanol in my gas ? Sometimes if I disconnect the battery and reset everything - she starts just fine. Any help would be appreciated. Thanks

[jjgag60]

Incresing idle speed

I would not touch the idle screw, usually it has a red cap over it and it is for a reason. The TPS on our boats is not adjustable so the orientation of the idle screw tells the computer what to do. I read somewhere on our ECC- IV systems, we are either a closed or open loop so when the boats starts, it does not use the ECC (computer) to start. Once it is running, then the computer starts getting readings from the sensors. You should check the ECT and the ACT sensors they cost about $18 each and are a lot cheaper than the MAP and the TPS. NAPA can order the parts for you. The ACT sensor reads the amount of air flow coming in and tells the computer how much gas to give it. Print the manual for the Gt-40 off this website. It tells you all the spec on what voltage the sensors should be and how to check your MAP sensor. I would also pull some of the spark plugs and check their color. They need to be the color of a brown grocery paper bag or spark plug white. If they are black then you are running rich. The local dealer can hook your motor up to a “STAR” tester and it will check all the sensor for you while it is running. If you replace any sensor, make sure you disconnect the battery for an hour, so the ECC shuts down. We have a learning ECC and it will revert back to its old setting for a couple of on/offs before you will see a change in what you replaced. Let us know what fixes your problem.

[eseybold]

plugs all look fine.....unfortunately, before reading your advice, I turned the idle screw a bit and it seems to have solved the problem for now. Tomorrow I will turn it back to where it belongs and remove my ACT sensor and get a replacement. In addition I will clean my spark arrestor to make sure we are gerting adequate air flow . I appreciate the advice....

[2gofaster]

The ACT reads air charge temp, not amount of air, on a speed density, open loop, Ford EEC based system, which is what the GT40 is. It calculates the volume of air ingested based on the pressure read by the MAP and the temperature of the air(ACT). When you crank the engine, the system sets the IAC(idle air controller) at a certain opening amount and that, along with the air vented passed the open throttle blades, should give enough air to start the motor. So in this case, either the throttle blades have moved a bit(and this is possible just based on wear of the plate against the set screw), or the IAC valve is gummed up or sticking a bit. You can safely change the idle in a small range using the set screw on the throttle body. If that works, leave it. The other option is to pull the IAC and clean and/or replace it. But an IAC is about $70 whereas moving the set screw is free. As long as it doesn't surge, you will be ok. Surging comes from the TPS being misadjusted based on the opening rate/position of the throttle body.

[eseybold]

It was a fuel relay....I think

........ BTW I neglected to let you know that rarely, while pulling a skier at 34mph, the boat would abruptly and briefly lose all gas( half a second) then pick up again. As if someone shut off fuel for a second. Electronics still worked however during the brief hiccup.
Today I went to the boat ready to replace the MAP, ATC, fuel relays and TP sensors.
It started cold no problem. I let it run 30 seconds and shut it off while still cold. It took 4 crankings before it fired up again. So it is not vapor lock since the engine was cold. I then turned my idle screw back down to where it should be and cleaned my idle control valve and throttle plate. It started fine and idled very well at 650 rpm with no surges. I took it for a spin, got up to engine temp and shut it off.......it would not start despite multipl cranks. I disconnected the batttery to see if it would reset the ECM - no luck. I then replaced the fuel pump relay and bang - ran like a champ all afternoon with at least 5 start and stops - no problem. I will still replace the other sensors since I bought them and they were not too costly(about $35 each for MAP and TP sensor). For now the problem is fixed with the relay. I took the relay apart and I see nothing wrong with it but I did not volt test it.
Ironically when we were done skiing I went to hit the stop botton on the dash pad and the engine would not turn off ! I disconnected the ignition module to shut it down and took my key pad apart and dried it - as of now everything works just fine.............thank you for your help !