Loss of power

[androu]

I've read through all the threads about engine problems with hard starting, etc. and the spark plug cap issue, and everything else I could find. I didn't see anyone else describing the exact problem I'm having, so here goes. At highway speeds, fifth gear, around 75 or so, temperature around mid-range (i.e. normal) I have experienced what I would call a lack of throttle response. The engine doesn't die or sputter, I'm just unable to accelerate, even with full twist of the throttle. If I gear down, I can get the revs higher, but still no increase in speed. It's almost like the speed limiter most newer Japanese bikes have now, execpt at around 70-75 mph. If I pull over and shut the ignition off, the bike will restart immediately and function normally, and I may not have the problem again for several days. It's happened about 4 times now and is quite sporadic, happend twice on one ride, then not agian for a long time. No engine warning light or any other abnormal indications, just lack of throttle response. Never happens until I'm on the road for a while at high speed, engine good and hot. I can ride around town and it never happens, only out on the highway at speed. Ideas? I guess I could swap out the plug caps since that's a known issue with at least some of the 2010 models, and it's pretty easy and cheap, but I'm not confident that's the probelm.

 

[Phil Tarman]

Strange...very strange. Have you talked to a dealer? I'd try the plug caps, I think, but I have no idea if they'll help or not.

 

[Warren]

I really have no idea but at 75 mph on the highway as compared to the city you are asking for a lot more fuel delivery. It almost sound like fuel starvation. If it were an old bike I would say check your gas cap vent but with a fuel injected bike I am not sure if that could be the problem or maybe its the fuel pump. I would take it to the dealer.

 

[androu]

I really have no idea but at 75 mph on the highway as compared to the city you are asking for a lot more fuel delivery. It almost sound like fuel starvation. If it were an old bike I would say check your gas cap vent but with a fuel injected bike I am not sure if that could be the problem or maybe its the fuel pump. I would take it to the dealer.

Yeah, it feels like a fueling problem when it's happening. It may have happened at slightly slower speed as well, maybe 65-70ish and is always "fixed" by shutting off the ignition and re-starting which makes me think it's an electronic issue rather than an actual clog or venting problem with the fuel system. It's tough to troubleshoot since it only happens sporadically. I think I'll take it out this weekend and try to duplicate the issue and pay more attention for any signs of a cause this time.

 

[Rmcapozzi]

Can you swap ECMs with another NT in the area?

Yeah, it feels like a fueling problem when it's happening. It may have happened at slightly slower speed as well, maybe 65-70ish and is always "fixed" by shutting off the ignition and re-starting which makes me think it's an electronic issue rather than an actual clog or venting problem with the fuel system. It's tough to troubleshoot since it only happens sporadically. I think I'll take it out this weekend and try to duplicate the issue and pay more attention for any signs of a cause this time.

 

[dnktng]

It's tough to troubleshoot since it only happens sporadically. I think I'll take it out this weekend and try to duplicate the issue and pay more attention for any signs of a cause this time.

I was getting a temporary loss of power at ~60mph when the NT was have MAP sensor problems and a possible air leak under the rear throttle body due to a loose band clamp. From what I remember the loss of power was about 5 seconds or less and I never noticed a MIL when it happened, but the event was stored on the ECM. I suspect that the ECM was getting the MAP sensor fail and going into the Fail-Safe mode which does limit engine speed. Not sure what revs it is limited to, but I recall between 4-5000 rpm. I never noticed the MIL come in and clear while trying to control the herky jerky motorcycle, plus glare, and other things occupying my mind when everything is going wrong. If you haven't already done it, it may be a good idea to see if your ECM has stored codes that may have been missed.

If you haven't replaced the original spark plug caps, that can only help. They are cheap... Honda part number 30700-MEW-922.

Agree the problem behaves like lack of gas issue also.

 

[androu]

I was getting a temporary loss of power at ~60mph when the NT was have MAP sensor problems and a possible air leak under the rear throttle body due to a loose band clamp. From what I remember the loss of power was about 5 seconds or less and I never noticed a MIL when it happened, but the event was stored on the ECM. I suspect that the ECM was getting the MAP sensor fail and going into the Fail-Safe mode which does limit engine speed. Not sure what revs it is limited to, but I recall between 4-5000 rpm. I never noticed the MIL come in and clear while trying to control the herky jerky motorcycle, plus glare, and other things occupying my mind when everything is going wrong. If you haven't already done it, it may be a good idea to see if your ECM has stored codes that may have been missed.

If you haven't replaced the original spark plug caps, that can only help. They are cheap... Honda part number 30700-MEW-922.

Agree the problem behaves like lack of gas issue also.

I'll check the code for sure. I doidn't realize they could be stored without the MIL.

 

[androu]

Yeah, I thought about the fuel pump but it seems weird that it works fine after I stop and restart the engine. Worth looking into though.

A common issue on the Deauville forum is the fuel pump failing. You'll still get fuel because it'll be gravity fed, but you won't get enough at high speeds. Also, you'll lose part of the capacity of your fuel tank.

Chris

 

[NoVa Chris]

Do try the spark plug caps. The fact that the engine needs to get hot (which of course heats the caps) is the one indicator that points to the caps. The actual symptom your are experiencing does not sound like caps. They tend to produce a more dramatic high RPM loss among other symptoms. Main thing is they are cheap and easy to swap, so I would start there.

And you don't even need to get the Honda replacement caps. I put in a pair of NGK angled resistor caps (VDO5F), from my dealer, for about $6 each. They have worked fine.

Please do report your results!

 

[seagrass]

I would strongly suggest it is a fuel problem. My guess would be a blocked fuel filter or a faulty fuel pump that fails to provide enough flow at high speed after a period of time. Turning the ignition off and back on may allow the fuel pump to operate again at full flow.

I know of a problem where there was a foreign object in a fuel tank and at high flow rates the object was sucked against the fuel pump and restricted flow, once the ignition was turned off the object fell away from the pump and fuel then flowed OK until the next time it happened. I do not suspect this is your problem but it is interesting to note what can happen.

 

[mikesim]

I think the relay and gravity feed issues on the Deauville forum apply only to the older carbureted Deau's. If the fuel pump heads south on a 700, you are dead in the water, Does the bike simply refuse to accelerate more, or does it fall on it's face when WOT is applied? If it is simply a fueling issue then I would suspect the bike will fall on its face since with the throttle open a lot more air is introduced with no corresponding increase in fuel.

Mike

 

[DirtFlier]

Checking for fault codes stored within the bike's computer is a good starting point but I'd still replace the plug caps if they are original.

Recently, I had two no-start situations while on a 4-day trip to the Blue Ridge Mtns. Each time I was able to get the bike restarted then the bike ran normally and the MIL light never came ON, probably because it was an intermittent failure. Once home I checked for fault codes and it showed #19 (Crank Position Sensor) so I replaced that part and it's been OK since then.

 

[Rmcapozzi]

That's kinda where I was with the fuel pump too. Seems more sensor/engine management to me based on it not "falling on its face" at WOT.

Checking for a stored DCT is a good idea. A strange issue for sure.

I think the relay and gravity feed issues on the Deauville forum apply only to the older carbureted Deau's. If the fuel pump heads south on a 700, you are dead in the water, Does the bike simply refuse to accelerate more, or does it fall on it's face when WOT is applied? If it is simply a fueling issue then I would suspect the bike will fall on its face since with the throttle open a lot more air is introduced with no corresponding increase in fuel.

Mike

 

[androu]

I think the relay and gravity feed issues on the Deauville forum apply only to the older carbureted Deau's. If the fuel pump heads south on a 700, you are dead in the water, Does the bike simply refuse to accelerate more, or does it fall on it's face when WOT is applied? If it is simply a fueling issue then I would suspect the bike will fall on its face since with the throttle open a lot more air is introduced with no corresponding increase in fuel.

Mike

It doesn't die, it keeps running but gradually slows down and can't accelerate at all. The first time it happened I was going up a slight grade, so tried to give a little more throttle to maintain speed and just couldn't, even wide open.

 

[androu]

I'm going to go ahead and swap out the plug caps, since I already have a pair, and try some highway riding this weekend. I'll report back next week.

 

[mikesim]

Plug caps won't hurt anything, but likely will not fix anything either based upon the symptoms you describe. Try to get the fault codes from the computer if there are any stored in it. My SWAG diagnosis would be a MAP sensor based upon the symptoms you describe. But, anyone's guess is as good as mine without any evidence of failure.

Mike

 

[androu]

OK, I checked the codes via the MIL flashes and got nothing. MIL just stays illuminated with brown wire jumped to green per the manual. Changed the plug caps and rung it out pretty good this weekend, lots of high speed cruising on the highway in around 100 degree temps with no issues. I'm still not 100% convinced, but so far, so good.

 

[elizilla]

The NT's fuel pump is cooled by the gas around it in the tank. Does this happen when the tank is somewhat less full, and there's less cooling for the fuel pump? Maybe the fuel pump has a heat related issue.

 

[charlie b]

It does sound a lot like a fuel starvation issue.

When it slows does it feel like one cyl isn't firing or do both quit? If only one then I'd look at injectors. (it may not be obvious that it is a single cyl dropout with the muffler on the NT, have to carefully notice change in firing frequency).

I'd also not rule out a computer/sensor problem, even with no codes.

 

[androu]

Nope, has happeded at various fuel states, including mostly full.

The NT's fuel pump is cooled by the gas around it in the tank. Does this happen when the tank is somewhat less full, and there's less cooling for the fuel pump? Maybe the fuel pump has a heat related issue.