Engine dies at idle

[jmstige]

I was out yesterday and after about an hour of surfing/stop and go type operations - the motor died on me at idle. After starting it up - it idled just fine and we drove back to the slip. While parking it - I went to bump it into reverse and it did it again. Luckily we were able to grab the boat and all went well there.

The boat has NEVER done this before and it has me concerned. Would low battery levels cause something like this? Is there anything I can check this AM before we head out. I was just going to make sure both batteries had a full charge.

[hoopykat]

Not likely a battery problem, as the batteries only start the boat and power the stereo and other accessories. Once the boat is running, the alternator supplies power to the engine. Could be bad gas, or water in the fuel, or a dirty fuel filter. Maybe the idle speed is too low. Start there and see if it idles better.

-Mike

[jmstige]

Well - maybe bad gas...I said batteries because it seems like we have starting problems when the perko switch is in the 3 or 9 o'clock positions - but if we have it in the 6 o'clock position (both batteries) - we start up right away every time.

It only did it once today at the end of the day (almost to the slip) and I was going to neutral a bunch to see if it would die. It never did when I tried to reproduce the problem. It only seems to want to die at critical/unexpected times.

I guess I'll monitor it for another tank of gas - but if the problem continues, would the fuel pump be a reasonable replacement? We are planning on pulling it out and doing a fluid change/plugs/cap/rotor in the next couple of weeks anyway.

[jmstige]

Well - it hasn't really died on us like this for a couple of weeks - but we have developed another problem right around the same time...

At random times - it takes 3-7 times to get it started after shutting it off when picking up a boarder. When it does start - it sputters and runs like crap for about 5-10 seconds until it reaches 600 rpm and then all is good. The next time we stop / start - it starts on the first crank and runs great right away.

We have run thru a couple tanks of gas, changed plugs/cap/fuel filter...

I'm now starting to think fuel pump/cooler/regulator. The problem I'm having is that I've read all the threads on vapor lock - and it isn't doing what is described there...Never a problem bogging down when accelerating when hot.

The only thing is - this problem has started when it got real HOT down here in TX - like 101-105.

I've changeb out the easy/cheap stuff - the fuel pump/cooler/regulator is more expensive when I'm just guessing at the problem.

Any suggestions on isolating this sort of problem? I'm really trying not to take it to that $90 / hr place to find the problem.

[jsz]

By any chance, is there black dust around the motor? Belt dust from my Goodyear Gatorback belt caused me stalling problems that took me a while to figure out. After putting a normal belt on and cleaning the IAC (idle air controler) the stalling went away.

[lee]

Try cleaning or changing your IAC.

[dogbert]

Is that a DIY, lee?

[lee]

Yes it is. The IAC is mounted on the intake manifold right by the air intake. It will have two wires hooked to it. The IAC can be cleaned with carb cleaner.

[dogbert]

Thanks!

[Fast1911]

Possibly an alternator going bad?

[dogbert]

It's probably the IAC.

BTW, this happened to my neighbor's '02 21v the other day. Our dealer's service manager says they've been seeing a lot of this lately. Not sure if it's heat related (we've had 40+ 100 degree days).

[jmstige]

I think that resolved the issue...Thanks everyone.

I cleaned it out w/ some carb cleaner on Saturday and it started just fine all weekend...

It was much cooler this weekend, so I'll need a 100+ degree weekend of use to be 100% sure the problem is gone.

[jsz]

Did you notice if there was black dust over the motor? If so the IAC will clog again. I'm speaking from experience here. A different belt helped but I'm wondering if a pulley is slightly off. There is another post here on how to check for that.

[chuckhoenig]

Would someone be able to post a pic of this? I'm having the same problem, and was unable to find it on my motor. I replaced the fuel water separator last year, and I'm going to do it again this week.

I've got an 03' 21i with a 350 MAG MPI.

Thanks!

[ereed969]

I am having simailiar problems. I have black dust all over from the belt. My boat shuts down after cruiseing for about 30-40 seconds. Does anyone thing that I could have the same problem