Throttle problem

My 04' has developed a problem that only happens when she is real hot. It initially shows up as a little hesitation when the throttle is turned. 5-15 mins later it loses power and when you open the throttle appx. 3/4 she will run better but not good. As this progresses over the next 1/2 hour it is more and more difficult to keep her running by twisting the throttle.

At highway speeds she is barely manageable to keep running but the road speed will keep her going with a lot of twisting the throttle. The on/ off action of the throttle is so violent that running in lower gears can be very exciting/ dangerous! It almost feels like something cutting the ignition on/ off or an issue with the TPS (throttle position sensor) getting confused when it gets real hot.

If I shut off the ignition it will run normal for 10-20 miles and then it starts over. Once she cools down for an hour she will run normal. Does the ST13 have error codes? Maybe it is recording this issue. Right now I'm 300 miles from home (in STL) and going to start home early Sunday with the hope that the cool morning will help.

Any ideas would be appreciated. I'll try and get into the Dealer next week but it will be real hard to diagnose something that is not happening unless she has been run hard for 3-5 hours.

Time2Sleep
Neil S.

Since your out of your normall area is it possible you got some H2O with one of your last fill ups?

The bike will store error codes but I'm not familiar with their retrieval.

The only other thing I can think of is stopping the bike with the kill switch, which if I remember correctly will have the ECM start fresh with the next start. If it has had a hicup it should clear it and run fine.

To late for me to think of anything else.

I'm sorry to say I don't have any helpful ideas.
Please let us know what the trouble is once you get it sorted out.

A vacuum leak can give some of these symptoms.
But, I don't see any of your modifications affecting vacuum.

You can get the error code by using Jeff's technique (thanks Jeff!).

Good luck!
Mark

i would try to put in the stock FPR back in and see if the problem clears up. sounds like its getting to much fuel. pull the plugs and see if they are black indicating a very rich mixture.
mike

Mike, I thought about the FPR but, the symptoms are too on/ off for them to be a result of the FPR. If the bike had drivability issues sluggish, low power, slow to fire it could be the FPR loosing it's setting. FPR's are pretty simple devices: Spring, diaphram and a little vacuum ( I used to manufacture about 15k/ day FPR's for GM back in the 90's). When you have higher vacuum ie: closed throttle, it reduces the fuel pressure otherwise you might run rich in that scenario.

This could be coils breaking down, crankshaft sensor, TPS or mass flow sensor being affected by the heat. Maybe an O2 sensor, althought most EFI systems have a limp home mode if the 02's are not reaading correctly.

I'm still in STL, spending time with my 85 yo Mom. I'll head back to BNA tomorrow AM, early.

Neil S.

my money is still on a vacuum leak. It can look like a computer failure (Rod Hephner had an issue with a vacuum line to a cruise control) until the leak is found.

I have read that people hunt for vacuum leaks by spraying wd40 and listening for idle speed/engine noise changes.

Mark

Your problem sounds like a fuel issue and not an electrical problem. If you have some way to connect a pressure gauge to the fuel system after the filter, that will indicate whether or not the fuel pressure is eratic. Causes are most likely a fuel pump or obstruction in the filter or injector(s). I don't think a vacuum leak would be as severe as you indicate (not running up to 3/4 throttle) unless it was on 2 or more throttle bodies.

If the TPS was faulty or giving incorrect readings, the FI light would be lit or blinking.

I'm going with the FPR being faulty or a air leak to the FPR vacuum line.

Dave, Desty:

I agree with both of you. I have been in contact with some of the "Pros" around and they also think it's fuel pressure related or, maybe a vapor lock scenario. Since I'm not that familiar with the OBD on the Honda I will have to bow to the experience of others. I have heard that I am not the only one that has had similar issues.

Possible issues:
Fuel filter (limiting flow to fuel pump, changed Jan06')
Fuel Pump (due to age not pumping as well as new and even less flow when hot)

Today I will contact my Svc Mgr and see what he thinks and what course of action he deems necessary. Hopefully they have the portable scan equipment that they can hook up and ride with.

More to follow.

Neil S.

Just out of curiosity... has the tank been up lately to change the air filter? If so, it's possible that the vent tube was pinched putting things back together. It's very easy to do and would act like a fuel problem.

I think Mageerc is on to something. You might try to open the fuel cap next time it does it and see what happens.

opcorn opcorn opcorn

Let us know what they find.