GT-40 Surging at Start-up

[jedgell]

I have a ’95 w/ the GT-40. Its always starts right up when its cold. My problem is after it has sat for about 30-60 minutes after it’s been run. When I start it after it’s had the 30-60 minutes off, it starts OK but immediately starts surging. It will surge between 500 and 1500 RPM’s, it does this for about 30 seconds, and sometimes quits. The engine is running smoothly, its just not maintaining a constant RPM. Most of the time I have to turn the boat off and back on again to fix it. Other than that small problem the boat runs great. Another member at the lake has the same problem with their Nautique w/ the GT-40, though I think its worse on mine. Could it be the idle control valve/motor? If so how can I fix it? Its not a huge problem, but can be annoying. Thanks in advance for the help.

[skinautique]

Do you have cruise on your boat?

[jedgell]

Yes, I installed PP over the winter, but the surging problem was happening before I installed the PP. It doesn't surge while driving, only right at start-up.

[NautiqueJeff]

Since it was happening before your installation of Perfect Pass, this probably isn't your cause, but you can do one quick check on your PP installation just to be sure that it isn't contributing to your problem. In the photo below, make sure there's no gap between your Perfect Pass cable and your throttle cable when your boat is in neutral. This is a common cause of engine surging in neutral. It probably isn't your cause, but it is a quick thing to check.

[skinautique]

It is hard to say what it could be with the EFI system. It could be a number of things. I honestly don't know what to suggest without being able to hear it.

[ag4ever]

I would think it is the idle control motor. Fords were notorius for having a surging idle when that was dirty. You might try cleaning it with carb cleaner.

[nms1991]

Jedgell you may have to take into a dealer to find out what it is, I know there is a good correct craft dealer in texas that could fix it with the correct books and knowledge of the ford efi system

[jedgell]

Where is the idle control motor, and how do I clean it? Can I just spray carb cleaner right on it?

[nms1991]

It is on the throttle body unit where you mounted you cruise control cable to. it is on the side facing the back of the boat. it should have only two wire coming out of it. Yes you can use carb cleaner on it but i would use a throttle cleaner for fuel injection.

[vortech347]

I have the same problem on my 99 w/GT40

I have had this problem since the first year owning my boat. I took it in 3 times to the dealer under warranty. They checked the TPS, replaced the thermostat since it was running very cool and checked fuel pressure, idle speed, etc.

Nothing fixed it.

I am going to clean the IAC to see if it helps. I also just put in new plugs and have been running a lot of fuel injector cleaner through the motor to make sure the injectors are clean. It seemed to run better yesterday but it still surged and did die one time.

I have a call into my dealer to ask the techs what they think. Once I find out what they have to say I will post it here. Since they looked at it 3 times under warranty they should be pretty forthcoming with info for me to fix it myself.

[jedgell]

I tried to clean the IAC, but didn't know how to do it. I removed the IAC from the throttle body and sprayed some throttle body cleaner in it, but it didn't help. Is there a better way to clean it? If the problem is the IAC its probably worth replacing it, depending on how much it costs. A friend has the same year w/ the GT-40 and it does the exact same thing. It only does it when the engine has run for a while and gets hot, then cools down for about 1/2 hour. Anyone know what else could be causing the problem? Thanks for the help.

[AirJeff]

Anyone find a fix for this one? We just picked up a 2002 with the GT-40 and have the same problem from time to time. We've put about 10 hours on it and I would say it does it about 30% of the time, never killed though. I've just rev'd her up a couple of times and brought it back down and the engine idled fine, anoying though.

[MNSuperAir]

Did anyone find a cure for this? I have the same problem. It does go away once underway but surges at initial idle. It has died in the past also.

[hwajr]

I have a 96 GT 40 that has been acting the same way. In addition it bogs on acceleration and will not exceed 3500 RPM. I called PCM and spoke with Mark (803.345.1337x108) who is their GT 40 technical guru.

He said it sounded like a fuel pump issue and suggested testing the fuel pressure, which should be at 38-42 at idle. Had it tested and the reading was 20. The mechanic said considering the age of the boat that both high and low pressure fuel pumps should be replaced.

They were ordered today and will post up on results. Pressure regulator was previously replaced with no improvement.

[AirJeff]

hmm, makes me wonder if it could also be caused by a dirty filter....Which reminds me, I should change mine.