can anyone diagnose engine ‘surging’ prob?

[NewTo700V]

It sounds like to me that you are not building up enough pressure on the fuel rail to support the engine under a load. This could be directly related to fuel flow. A restricted fuel flow will not allow the pump to build up to the required normal operating pressure.

I would suggest that you do the Fuel Flow Inspection called out in 6-41 in the OEM Honda Shop Manual.

I really don't think it's fuel. His bike is running fine for half an hour or so. If it was a fuel presure issue that would be showing as soon as he hits the road. Also the bike is specifically complaining about TP sensor voltage with the MIL light.

I'm really betting on a connection issue. I went through this exact scenario a few months ago. Testing the TP sensor as per the shop manual is a waste of time. Get to the connectors, unplug them. Give a little spray of DeoxIT to the pins, allow to dry. Put back together and go ride.

 

[toowired]

I really don't think it's fuel. His bike is running fine for half an hour or so. If it was a fuel presure issue that would be showing as soon as he hits the road. Also the bike is specifically complaining about TP sensor voltage with the MIL light.

I'm really betting on a connection issue. I went through this exact scenario a few months ago. Testing the TP sensor as per the shop manual is a waste of time. Get to the connectors, unplug them. Give a little spray of DeoxIT to the pins, allow to dry. Put back together and go ride.

if it helps w diagnosis i would say that ‘sputtering’ is not the best adjective in this case. it’s more like sudden decrease in throttle although without retarding throttle. natural rider reaction is to increase throttle. after 1 to 3 seconds, engine suddenly roars back. runs ok maybe 30 seconds or more, maybe a minute or two, cycle repeats.

yes, bike runs great first 20 minutes or so. then engine light comes on, problem starts and persists remainder of ride. way earlier i confessed i let the bike sit too long without starting or riding (on battery minder though, started just fine). hence i originally thought problem to be bad gas.

 

[Brillot2000]

if it helps w diagnosis i would say that ‘sputtering’ is not the best adjective in this case. it’s more like sudden decrease in throttle although without retarding throttle. natural rider reaction is to increase throttle. after 1 to 3 seconds, engine suddenly roars back. runs ok maybe 30 seconds or more, maybe a minute or two, cycle repeats.

yes, bike runs great first 20 minutes or so. then engine light comes on, problem starts and persists remainder of ride. way earlier i confessed i let the bike sit too long without starting or riding (on battery minder though, started just fine). hence i originally thought problem to be bad gas.

The fuel system is simplified to Supply, Pressurize, and Delivery. Supply is the fuel tank and is constant. Therefore the factors that really come into play are pressure and delivery. The pump pressurizes the fuel and the fuel injectors deliver it. The Throttle Position (TP) sensor is the key to telling the ECU the position of the throttle and has a direct effect on the amount of fuel that is delivered at any given time.

This could be a longshot, have you replaced the spark plug caps recently? There has been a known issue with defective spark plug caps. This could be a possibility as the resistor in the plug cap will heat up. A bad resistor will change its resistance, which in turn could affect the spark intensity and engine performance. I am just saying.

If the engine light or MIL as it is referred to. There will be a code stored in the ECU. Typically it can be checked with the engine not running, kill switch on, and with the side stand down. The MIL will blink in a series to get a code number. Long blinks are equal to 10 and short blinks are equal to 1. 1 Long blink followed by 8 short blinks would get you a code of 18.

 

[ARKNT]

Always check simplest things first. Hope you have a garage that isn't too cold right now.
With engine code 8 the computer thinks the throttle is closed so it defaults to engine map setting for closed position. At least seems to fit your symptoms. I would first continue on TP checks.
System charging/battery voltage. Then move on to the TP connections and sensor checks while you are in there in position to measure them. Your failure seems to be regular so that may make it easier to find than some of the more intermittent failures.
There seems to be a few reported connection issues so look close there.
If that isn't it move on to other possibilities. Good luck.

Brad

 

[toowired]

Always check simplest things first. Hope you have a garage that isn't too cold right now.
With engine code 8 the computer thinks the throttle is closed so it defaults to engine map setting for closed position. At least seems to fit your symptoms. I would first continue on TP checks.
System charging/battery voltage. Then move on to the TP connections and sensor checks while you are in there in position to measure them. Your failure seems to be regular so that may make it easier to find than some of the more intermittent failures.
There seems to be a few reported connection issues so look close there.
If that isn't it move on to other possibilities. Good luck.

Brad

hi brillot2000 i get code 8.

brad, sorry if it’s a dumb question, there’s been a lot of info flowing. what would be the TP checks to perform before checking the connectors?

 

[moriniman2011]

Cheapest simplest thing first is to change the plug caps for NGK ones at a few bucks each (standard procedure on almost every NT700), then just check the connections into the airbox are as well as the ECU. Other engine/electrical bits apart from the regulator/rectifies and its connector and the starter switch very very rarely give problems - though I realise there is a MIL light showing on this occasion.

 

[NewTo700V]

Plug caps are not going to cause at speed hesitation and flash 8 TP MIL. The symptoms for the plug caps that prompted that service bulletin years ago were rough idle at higher temps. You guys are sending the poor dude all over the bike. The bike says TP sensor and hesitates. Start there by cleaning connectors and putting back together, there's nothing on them to "check".

 

[Phil Tarman]

A great big Plus One to what NewTo700V said above. That fixed mine according to the tech who did the cleaning/checking/putting back together.

 

[mikesim]

Plug caps are not going to cause at speed hesitation and flash 8 TP MIL. The symptoms for the plug caps that prompted that service bulletin years ago were rough idle at higher temps. You guys are sending the poor dude all over the bike. The bike says TP sensor and hesitates. Start there by cleaning connectors and putting back together, there's nothing on them to "check".

Amen!! The MIL is providing you a clue! It would be in your best interest to pursue that clue first before you resort to guess work!

Mike

 

[Brillot2000]

hi brillot2000 i get code 8.

brad, sorry if it’s a dumb question, there’s been a lot of info flowing. what would be the TP checks to perform before checking the connectors?

MIL Code 8 specifically points to the Throttle Position (TP) Sensor. The "Voltage High/Low" refers that the ECU is not seeing any changes in the voltage being read back by the ECU. That part is not listed separately on the Honda microfiche and is sold on the throttle body assembly. I think that someone here on the forum found a part number for a replacement part. You'd have to do a little searching to prevent spending up to nearly $900 for new a replacement throttle body.

The clue to me is that the bike runs fine when cold. Either a connection is developing a high impedance connection when heated or the TP Sensor itself is failing after being heated up. I quick way to check it would be to use a can of Dust-Off Duster. Hold the can upside down and spray the liquid coming out directly into the TP Sensor. The fluid will freeze the sensor and drop its internal temperature. If the bike smooths out and runs good again. BAM, There's your problem, the sensor is bad.

Good luck on your quest.

 

[ARKNT]

You don't need to do checks on TP before doing connection checks, basically at the same time since you will be at the connection locations. The service manual (you may not have yet) has some voltage checks to do. Voltage supply and output volts. You probably need the manual for the specifics, wire colors etc. With the sensor itself unplugged the resistance should be .5 to 1.5K ohms. (assuming you have a multi meter) Keep in mind yours may be somewhat intermittent since it fails after warm-up.
You may fix the issue by unplugging/replugging the connectors, cleaning the contact points as they are manipulated. If so good idea to use contact cleaner and a little grease to prevent later corrosion of the contact surfaces.

Brad

 

[dnktng]

if it helps w diagnosis i would say that ‘sputtering’ is not the best adjective in this case. it’s more like sudden decrease in throttle although without retarding throttle. natural rider reaction is to increase throttle. after 1 to 3 seconds, engine suddenly roars back. runs ok maybe 30 seconds or more, maybe a minute or two, cycle repeats.

yes, bike runs great first 20 minutes or so. then engine light comes on, problem starts and persists remainder of ride. way earlier i confessed i let the bike sit too long without starting or riding (on battery minder though, started just fine). hence i originally thought problem to be bad gas.

The way I understand it, and I could be wrong, but...

A TPS error code also has a fail safe of 0 Degrees. So when your ECM detects a TPS error (either hi or lo volts....not a proper signal detected) and gives the MIL, it also substitutes a signal to the ECM that the throttle position is 0...shut. After the ECM detect normal signal from the TPS 1-3 seconds later as you describe the normal TPS signal will be reinserted to the ECM and away the engine goes.

While you have the TPS error and MIL you still can rev and ride. I believe the engine will actually rev above idle because the actual throttle valve is really open, but the ECM sees the throttle as shut and should inject less fuel...and rev lower than expected for the actual throttle position.

It sounds like you have an intermittent TPS error, likely to be caused by wiring connectors. If it isn't wiring connectors from the ECM to the TPS...then it may be the TPS and thing get difficult and more expensive.

 

[Brillot2000]

I found the thread and the post where a member used a Throttle Position Sensor from a Yamaha, P/N 1SL-85885-02-00. Refer to post #16, Throttle Position Sensor TPS Part Number.

The JT7H TPS is used on the Honda Element, Accord, CRV, and Acura RSX just to name a few. Since this part is for automotive use, the price drops below $20. There's a long list of these parts available on eBay, throttle position sensor JT7H.

Just in case you need one.

Hope that this information is useful to you.

 

[Hondafan]

That is great information for all of us. Thanks for taking the time to find and post it.

 

[NewTo700V]

I think it's great you guys know where to find and follow test procedures, but in your enthusiasm some are completely glossing over a key line Honda themselves put in the service manual at the very beginning of the Ignition chapter. :ROFLMAO:

This is word for word from the service manual. It's bullet point number 7 under Ignition System; Service Information; General:

A faulty ignition system is often related to poor connections. Check those connections before proceeding

 

[davis_ecd@yahoo.com]

So do any of the JT7H Honda car TPS actually work like the Yamaha part???

 

[WVRider]

Do the test that was suggested above and we will then have a clue on what to suggest. Your description of the bike baffles me however. I know the NT is not a powerhouse, but it is quite happy and comfortable cruising on the Interstates at 80-90 mph! How fast do you want to go? There are many of us who have over 100K miles on our NT's and have traveled to all of the lower 48, Canadian provinces and Alaska and if that's not "true touring" I don't know what is. If your riding style dictates keeping the bike at 5K rpm that's perfectly Ok and it won't hurt it a bit. Hondas like to rev. But I think you would find it a lot more relaxing to ride with the engine at a lower rev count. Unless I'm in hilly country, putting along at anything over 3K rpm is delightfully smooth and quiet.

Mike

Ditto to Mike's comments. 80 - 90 is easily doable. I seldom go less than 80 on interstates cause I like to be ahead of everyone and not get boxed in. Out west the two lanes are 75 mph and 80 was easy. Doubly baffled..

 

[DirtFlier]

If I rode around in 1st and 2nd gear, I'd also think the engine was surging! The bikes with fuel injection, including the NT700V, are very touchy to even tiny movements of the throttle unlike bikes with carburetors and this situation is magnified in the lower gears. Is this your first bike with fuel injection?

By the time I cross an intersection from a stop, I'm already in 2nd going to 3rd and and upwards, even in a town environment. There is NO reason to have the engine revving like crazy while going 35 MPH and it doesn't make it any safer - it just makes the bike more nervous and touchy. The speed you travel and the gears you use are two different things; to wit, you can ride in 4th gear at 35 MPH and nothing terrible will happen to the engine or transmission. You won't have the instantaneous acceleration of being in 2nd but do you really need that?

Avoiding a deer jumping onto the road is best avoided by using the brakes and swerving - you can't really do it with quick acceleration. And unless I have a need to do so, I don't downshift and use engine braking as I'm slowing for a red light. Most times, I'll downshift through the gears with clutch lever pulled IN and not use the engine as a brake.

When you go on your next ride, please upshift....upshift...upshift... You'll find your ride much more enjoyable.