scooby94

The yellow vacuum line that is attached to the top of VST tank goes down to a Tee and plugs into the bottom of the intake near the throttle body. The other line off the Tee goes to the mechanical fuel pump port. I ran the boat last night and it still is breaking up under a load going onto plane around 2800rpm and it will not go over 4500rpm. The fastest that I am getting is 53mph.

scooby94

I forgot, there seems to be NO vacuum leak at or around the hoses. The other yellow vacuum hose under the throttle body has vacuum and goes for where #2 cyl is to behind the throttle body. I don't understand why that line is there or what it is doing. My other ? is should I have vacuum on the yellow line on the top of the VST tank.

mats

Going back one step, summarizing the problem;
1. You get code 33
2. Plugs are black
3. Engine is breaking up at 2800 rpm. You only get 4500 rpm and 53 mps. Could you elaborate on "breaking up"?

What did mph and rpm did you get before?

scooby94

I was getting around 60mph, rpm I don't remember. The motor feels like it's breaking up around 2800rpm trying to go up on plane ( Breaking up = the motor is missing/stumbling/hesitating). Would a pickup coil inside of the distributor cause this. Not enough timing. Because on the baja's they have a hole in the hatch cover that drained water on top of the distributor. I have sealed that off since, but I had the problem before I sealed the hole up.

scooby94

I will also miss at some cruising speeds below half throttle.

Ted G

iTrader: (1)

Yes! I just had a problem with slight miss and tach fluctuation over 3500 rpm. Changed the module, no good. Changed out the distributor as a whole since I had some rust showing in there-PERFECT! I got the whole dist assembly for a 96 502 off eBay for 69 bucks brand new. I was thinking I would need to move the little screens when I got it but it already had them installed.

mats

I would start by checking fuel pressure when the engine breaks up ( check with the vacuum hose disconnected from the fuel pressure regulator). The pressure should be rock steady all the way up to WOT. If it is not you have all the classical places to look (filter in the VST tank, fuel pump, fuel pick up ,etc)

If that checks out I would check the ignition with a timing light. Check that the flashes are consistent in the break up situation. If there are misses you know where to dig further.

GOODT

ok maybe missing something here but if your worried about the yellow hoses dont they are just safety's....... in case the fuel pump diaphragm leaks or so if the vst needle sticks that


now that out of the way




are all the plugs black ?????

scooby94

All the plugs are black, except for #7, it is half black and half clean. I thought that the VST diaphragm was bad, but I checked that and no holes are in it and the spring is good.

GOODT

did you check your fuel press