gt40 EFI HELP

At the strt of the season my boat would crank, run a few seconds and shut down. After a lot of trial and error, luck and help from folks on this forum I found that the problem was that it was not getting enough air for combustion. I could pull off the pcv hose and it would run great just at a higher rpm. I ran it around the lake then hooked the pcv back up and it runs great,,,, as long as you don't idle too long. I have been trying to teach some grand kids to ski and that requires a lot of idling. After a few minutes it starts to run rough and shuts down when in gear. The only ;solution is to run it aroung the lake for a few minutes at 34-36mph then it idles fine for another few minutes. I feel like it is not getting enough air at idle to fully combust the gas so it builds up. I can smell it sometimes.. I have repaced the pcv valve and cleaned the spark arrestor . Any nuggets of wisdom will be appreciated, Thanks Don W

I guess it was "cured" for a month

I still think you have IAC related issues like maybe the passage around the throttle plate that the IAC regulates the air flow through is plugged or restricted and your throttle body needs a good cleaning especially that passage.

It's going in through the throttle body and at idle the IAC valve meters the air through an internal passage in the throttle body when the throttle blades are closed.

The valve gets a signal from the computer telling it how far to be open but if the passage is plugged it won't matter how far it's open.

Don

Quit naming all your threads the same, it gets confusing   

Now you have 3 with the same name

Here's a link to the thread from about a month ago for reference

link

It looks like he replaced the IAC valve, not sure how voltages were checked or what they were at different positions. as the manual talks about.

All good suggestions. I replaced the IAC valve early on and it was not the problem.It was then that I found out about the air because when I removed the IOC it ran fine, but when I put the new one on it did the same thing. How would I check for restricted airflow and clean it- injector cleaner? From what I have learned there are only three vaccuum hoses: one to the PCV, one to the map gas- (there is a filter here, white, about 3 inches long that I need to get off and check- and one to the fuel pressure regulator, which appears to go through the above filter and to the map gas sensor. Does that sound right?

Thanks. I like the idea of removing the throattle body and soaking it. There is a new wrinkle. Tried to ski this morning but The boat started surging and check engine light is on.Maybe if I can determine what is causing the light to come on....

Don W wrote: Thanks. I like the idea of soaking the throttle body. There is a new wrinkle. I tried to ski this morning and the boat started surging and the check engine light came on. Maybe if I can figure that out...

I had the stumble and surging when my LPP started to fail. I replaced it and the issue went bye bye. I do think your throttle body or IAC is acting up too. KENO is like a remote surgeon for this stuff.

With the IAC removed you can first blow some WD40 into the throttle body at the IAC mounting hole and then blow high pressure air hoping to clear the passage.
Finish by blowing Carb cleaner to remove any trace of the WD 40. IF you leave oil/WD40 in the opening it will attract dirt and clog again but I think the slippery WD40 may help clean out any crud in the passages.

You can hook up a Fuel Pressure gauge and watch pressure while you run the boat. I use a pressure gauge with a 5' hose so I can hook it up and place it somewhere to observe while it is running.   A second person can help and record what you witness. It is a quick way to establish fuel pressure and rule it out as a cause.

For many years now, 20 at least, I have been using a quart of ATF, automatic transmission fluid in my fuel injected cars and this boat. Put one quart in to a full tank and it lubricates and cleans the fuel injectors pretty well.   I use it about once a year.
Learned this trick from Diesel mechanics years ago.   It is cheap compared to FI cleaner and has smoothed out a few cars that had sticky injectors.
Some of the early FI cleaners were hard on the Orings but ATF has worked with no issues.
I am sure the EPA would not want it used as it is not approved. But it works.

Sounds like the original problem may be fixed but the new issue you first mentioned a couple of days ago is still there.

I think I'd check that all the connectors for the sensors are plugged in properly as a start and look at Lewy's post from yesterday.