5.7 GSI Starting, Iding issues

flaMtneer

Cadet
Joined
Mar 6, 2008
Messages
6
'99 VP 5.7L GSI PWTRCE, SN 4110186008, 550 hours

Sorry in advance for very long post, but I'm trying to give you guys as much background as possible. I have found several posts on here with similar issues but haven't found any that go all the way to a solution. I'm starting to think the shop working on this is stumped and they are very good as far as I know. I'm hoping someone on here can give me some ideas of what to have checked that we may be missing....so here goes...

First a little background - Blown head gasket in April 2011. Had head gasket replaced and head checked, valve springs R&R'd, New raw water pump, Tstat, plugs, o/f, fuel filter. All done by reputable shop. Began running only ethanol-free at this time.

Didn't run boat much last season, but when I did it seemed ok. (Maybe 10-15 hours)

April 2012 - First time out boat ran great for about 1.5 hours - pulling tubes, etc - then developed problem on hard throttle up where it would cough and sputter and there was a strong fuel odor in the exhaust. If I was very light on the throttle I could get on plane then boat ran fine. Took to shop (same shop that did head work) and they found injectors were dripping fuel which was laying on throttle plate and getting dumped in at throttle up causing engine to get too much fuel. Plugs were all fouled from running rich. Sent Throttle Body out for rebuild. At this time they also did the yearly service which included: Compression Test, Cap/Rotor, Plugs, Fuel filter, Impeller, Oil/Filter, outdrive service.

Picked up boat and first time out engine started, on first pass around the lake there was a single backfire, but it never happened again. Throttle up was much better but at times could still feel slight hesitation, but nothing like before. However, engine would not come down off high idle. After running for about an hour we sat and floated for probably 20 mins. When ready to head back engine would not start. Would crank, catch, then immediately stall. Finally after many attempts got engine to stay running by putting in gear quickly after engine caught. Other than high idle, single backfire, and no start boat ran fine.

Back to shop - they adjusted IAC and throttle cable and lake tested.

Picked up boat, went to lake. High idle gone, boat started immediately, but now had a small surge at idle speed and at times there was a sound like a pulley rubbing that disappeared as soon as I gave it throttle. The surging was not enough to really register on RPM gauge but you could still hear and feel it. After another hour or so of good running on plane engine coughed and sputtered under moderate throttle - one time - then ran fine (other than weird little surging at idle speeds). Stopped and floated for about 1.5 hours and then engine would not start. Exact same issue as before.

So...back to shop. They checked fuel pressure - pumps tested ok. Replaced anti-siphon valve which they said was causing the noise at idle. They also found one injector dripping fuel and sent TB out again for repair. This was 3 weeks ago. TB back on Tuesday, lake tested yesterday. Shop "Not happy with idling - going to try new IAC".

So, this is where I'm at. Since May 1st I've had boat in my possesion for maybe a week and have about 3 hours on water. I'm not a mechanic so I'm learning this as I go. Hoping someone has been down this same path and can offer solutions/suggestions.

Thanks!
 
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