gti le rfi hesitates on applying full power

[aviationfw]

I have just installed a rebuilt 787 rfi. I have run the diagnostic scan tool with no faults and reset the TPS with the tool. THe original TPS showed 7.6. now after the reset it shows -0.4 and runs much better I have 2 identical 2003 GTI LE RFIs. the other skis shows -4.4 and 3.6 for its TPS. It runs fine.
THe problem I am having is the new rebuilt engine runs fine at full power and all the way down to idle and back up as long as I use a smooth throttle pressure on acceleration. If I pull the throttle to full open very quickly, the ski does not accelerate and produces a lot of smoke. the spark plugs show rich mixture again an RFI engine no carb. eventually after maybe 7 seconds the ski takes off and accelerates to full power, this only happens on a quick pull of the throttle, a smooth pull has no problems and if a pull hard and the engine bogs down at low RPM then if I release the throttle to 1/4 and pull smoothly it recovers to full power. MY other ski same model will pull you out of bed with no hesitation when i applied zero to full throttle instantly. I have tried swapping rave valves swapping computers and new spark plugs, again the same problem persists. I also had the problem before I replaced the rebuilt engine. Any input on this problem would be greatly apppreciated to point me in the right direction for troubleshooting

[dsolie]

Re: gti le rfi hesitates on applying full power

Why did you have to install a rebuild?

[aviationfw]

Re: gti le rfi hesitates on applying full power

last engine had metal come off piston rings. I think may have been run dry of fuel and oil. during a fuel flow test with the injectors and spark plugs removed either that or just run dry of oil during operation. This is a rental ski and I only get to see it while at the resort. Best thing to do was to get a new SBT overhauled engine and start from scratch. Hence the rebuild.

[dsolie]

Re: gti le rfi hesitates on applying full power

Well if you are having problems with the filter or fuel pump, it may be causing a lack of fuel on demand for a throttle stab like that.

[aviationfw]

Re: gti le rfi hesitates on applying full power

I don't want to send you down the wrong path with the fuel pump testing that was just one of the many things we looked at to see if it might be a fuel problem. But the ski preforms well at full power for extended periods, so I don't believe it is a fuel pump or fuel filter problem. I just can't figure out why it hesitates from idle to full power it has no problem with a smooth acceleration or even 1/4 throttle to full power instantly. it is just that initial idle to full power quick pull that bogs it down. I would have put it down to bad technique on my part except my other ski does not have this problem when I reform the same test. i wonder if I close the rave valves if this would help fix the problem as currently they are at the recommended level position with the caps. I am a little scared to screw them dowm because this is a .5 oversize piston and i heard it may be necessary to sand the rave down in this case, i am hoping that they already have been sanded as during the rebuild we where not able to get the mto touch the pistons.
Thank you for your continued interest. my ski by the way is in the Philippines, our nearest service center is 1000 nm away by boat. hence all the questions.

[dsolie]

Re: gti le rfi hesitates on applying full power

Causes for hesitation.. Lean condition, issue with MPEM timing curve, poor port matching / port heights too high or low, fuel system issue, issue with stator timing, issue with injectors.

[aviationfw]

Re: gti le rfi hesitates on applying full power

Thanks for the reply, I have new injectors so that is not the issue had same problem with old injectors. I tried swapping the MPEM with other ski. Problem still there so it is not the timing curve. Stator timing I am not familiar with, but I have installed new rotary valve and double checked the timing angles they where good old engine had the same problem as well. Today we replaced the metal slide of the rave valves. Driving the ski it appears the problem has lessened somewhat but is still there. the census of my mechanic and I is that the engine is receiving to much fuel at once and is flooding before the engine has a chance to build rpm to burn the fuel. I noticed that the idle is very low and appears to be on oe cylinder. I believe this is normal for a GTI LE RFI to idle on one cylinder,
But the rpm appears low as it sounds like a knocking sound when it is at idle. It does not stall so I am thinking if I increase the idle rpm this might help with the pick up. Before you ask what rpm is, my gauges do not have any power, I have to trouble shoot this next, the local seadoo guy jumped the connecting plugs with scotch clips the little blue auto connectors a few months ago to fix the same problem, I guess due to pin corrosion on the plugs. I would have prefer just to buy a new set of electrical harness. But at least now I have a way to disconnect the power supply form the MPEM to the gauges and connect directly to the battery without feeding battery power back to the MPEM through the harness. I understand feeding power power back to the MPEM through the harness is a great way to trash the MPEM for good. I will update you with my next se of findings.