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2004 GTX 4-TEC Supercharged rough sub-idle cut out

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Grantthegreat

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Hello all!

I bought my GTX about a year ago at 118hrs and have since put about 40 hours on it. Didn’t properly winterize it, but I live in Mississippi and it didn’t drop below freezing for more than a few nights well into winter, plus the jet ski was stored out of the water (won’t forget to winterize next season). Come spring, I replaced the spark plugs, charged the batteries, replaced a bad starter relay, put some fuel injector cleaner in and it ran great for about 20 hours.

Then, I started having some issues starting it. The engine would turn over, but the RPMs never made it to the idle range, ~1800rpm, and the engine would cut out and die. So, I pulled out the spark plugs and they were decently black/fouled (they had about 20 hours on them already—we use the jet ski frequently), so I replaced them and changed the oil and filter when the filter arrived around the same time. Still the engine would crank and peak below idle rpm and choke and die.

I read on the forums always to check battery connections, so I did that. The previous owner installed a second battery to help power the Bluetooth speakers he installed. I noticed a connection broke to that battery, so I fixed that and checked both batteries to ensure they were fully charged. I don’t have a load tester, but both batteries were at or above 95% voltage-wise. Since the engine turns over and sounds like it wants to start, I don’t believe the batteries are the culprit.

Next, I pulled the spark plugs and they appeared to be wet and smelled like fuel. I set them down, covered the spark plug holes and went through the “crank engine” procedure to clear anything that might have been in there. By the time I went to clean off the spark plugs, they were not longer wet. I assume they were covered in fuel and it had evaporated. Reinstalled the spark plugs, and tried starting the engine (video below). It started right up! However, it was still idling rough and below idle rpm. After a few seconds, it cut out and died.


At the end of the video, you can see all of the white smoke coming out of the exhaust. It smelled like fuel, which made sense to me because of the several unsuccessful start attempts, I figured there would be excess fuel in the engine. However, it was still in the exhaust after I cranked the engine. After some research, everything points to coolant causing the white smoke. I don’t know what burned coolant smells like, though. Also, I haven’t noticed the coolant levels dropping (perhaps because the engine isn’t running long enough to burn a lot of coolant off), nor have I noticed any milky-ness in the coolant reservoir.

In summary, here are some symptoms:
-engine turns over, rpms don’t reach idle and runs rough, then dies
-white smoke in exhaust, smells like fuel

I constantly check for P-codes before and after trying to start the engine, but there aren’t any.

Some potential causes I have thought of:
-bad batteries (I don’t believe this is the case)
-faulty fuel injectors, injecting too much fuel (explains the excess fuel on the spark plugs when I pulled them)
-bad supercharger, not getting enough air into engine (previous owner said he replaced it with, I believe he said, one with metal blades instead of ceramic). But if it failed, I wouldn’t expect the engine would turn over at all.
-bad ignition system/coils (would explain the rough idling, maybe causing misfires, which wouldn’t ignite all of the fuel, explaining the excess fuel on the spark plugs)
-blown head gasket (most likely culprit—explains the white smoke, coolant causes misfires or abnormal rough rpm before cutting out)

Any tips or recommendations of things to troubleshoot next? I appreciate your help in thinking this over with me!

-Grant
 
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