Throttle Position Sensor glitch on 1999 VFR?

[Frederic Marchal]

My 1999 Canadian yellow VFR has about 128,000km. It has recently developed a hesitation or stumble when I turn the throttle slowly from a steady speed. Engine speed around 4000-5000rpm.

It clears itself up as you give it more throttle.

Doesn't happen all the time. In one given ride, it will do this a few times, then it won't happen for a while, then do it again.

Also, I get a visible puff of black smoke at full throttle. Not oil - the engine does not burn oil. Black, like running very rich.

My factory manual adresses a similar condition that points to the TPS. I'm going to follow the test procedure: checking voltage at the plug terminals.

The plug is under the throttle bodies.

Has anyone any experience with this?

If TPS is defective, can it be replaced? My Parts catalog doesn't list any pat number for the TPS.

Frederic

2000 Rosie

1999 Irene

VF500 '86 Junior

VF500 '86 Jr2

[Skidmark]

Fred, I have a '98 and as I recall the TPS is factory set on the throttle body. If the sensor is bad you may have to replace the whole throttle body, (unless someone knows of a trick I've never heard of). You may want to re-post this question in the 5th Gen forum. You'll get more responses there.

Also, check the flapper on top of the air cleaner. That air flap is designed to open at 5K rpm. There are two valves and a reservoir associated with that flapper.

Good luck

[HispanicSlammer]

If its an electrical fault with the throttle postion sensor you would have a FI light indication, most likely its just a dirty fuel injector, clogged and needs to be cleared. You can check for FI stored faults by shorting the blue taped connector on the left rear of the bike on the subframe then turning on the key, count the fi blinks if there are any.

Also there is a slight flat spot in the stock fuel mapping anyhow around that that rpm range, compounded by clogged injectors. I doubt its a TP sensor issue. Has the bike been sitting over the winter? Gummed up injectors probably.

[KanadianKen]

Could this be a fuel Pressure Regulator issue? Perhaps bumping up to the higher pressure might help?

[VFR Capt.Bob]

My bike has started doing this which made me think it was the battery going south. It just sputters like it's getting no fuel and will stall in city traffic. I just went through the wiring and charge system which seems fine so now I'm trying seafoam in the tank to clean out the injectors. Gonna ride it to work tommorrow and report back if it helped.

[kaldek]

None of you have considered the MAP sensor, your vacuum lines, or a starter valve synchronisation yet.

I strongly suggest you have a look at those. Check your vacuum hoses are connected, tight, and don't slip off the intake tracts unless you use a screwdriver. Then do a starter valve sync (because the MAP sensor is affected by these) and see how you go.

It won't help with the WOT rich running though - that's something else entirely.

[Frederic Marchal]

Thanks everyone!

It’s been a perplexing problem because it doesn’t happen all the time. I’ve focused on the TPS because the Manual’s trouble shooting guide point only to the TPS for my symptoms. There is a mechanical component in the TPS, and as I've spent a lot of miles with the throttle in the same range, there could be physical wear. The WOT smoke issue could also point to a faulty TPS.

Hopefully, the voltage readings will tell.

At any rate, my first line of attack is to go over the entire bike and check all connectors, hoses, MAP and PAIR circuits and sensors.

Over the years, I’ve routinely checked, cleaned and lubed most of the connectors within reach. Corrosion does set in! I use a dielectric grease on all connectors.

My Factory manual provides specs. for most everything. I can do volts and OHMs, but I don’t have access to the pin box for the ECU.

This I know: valves are adjusted properly, compression and leakdown are well within spec.

I’ve just synchronized the starter valves this winter.

The battery is good.

If it were the injectors, would you recommend one of those pressurized cleaner kits?

If it were the TPS, Honda won’t sell it to you unless you buy the entire throttle body. I’d need a second mortgage!

I’ve researched the web and found a site that sells replacements for Honda/Accura engines. One model looks the same and has the same JT3R number but a different suffix. I’ll research further as needed.

With thanks!

Frederic

2000 Rosie

1999 Irene

VF500 '86 Junior

VF500 '86 Jr2

[HispanicSlammer]

I doubt it could be the tps unless you wrecked it or took a hammer to the thing its pretty bullet proof. I got 124k miles on mine and its rock solid if your feeling play on the throttle thats more likely to be play in the cable rather than a bad tps. It would definitly have a fi indicator fault if there was physical damage that caused fuel issues, the ecm will detect out of spec voltages associated with the postion of the shaft any play there would trigger a fault. From what you saying your getting a spit of fuel at a certain throttle postion then it clears up as you move the thottle. It probably a lean part of the map then up into a fat part of the map, clogged injector is not atomized so its making it seem like a problem in the mechanism and its smoking as it adds improperly aired fuel. So please check for a code before procedding with the tps. do the easy cheap fixes first then move on to replacing parts.

I just took my fuel rail off and sprayed them out with carb cleaner then soaked them in seafoam overnight, bought a new set of seals for $30 bucks at napa autoparts, I have the part numbers in Kaladeks injector thread in the maint guides section. You need new orings and seals for each injector as recommended by the manual and put the throttle body back together, I hooked up the fuel lines and airbox and she started right up. Fuel treatments work too. But my way was rather effective on my issue, mine would not start at all and no fuel was comming out of the return line.

Used bikes and parted out bikes can be found rather cheaply, a guy here on vfrd sold a complete throttle body for a fraction of the oem price. Check ebay and the other big sites before trying to buy new parts like this.

[RollinAgain]

Does the bike have a Power Commander on it by any chance?

Rollin

[Frederic Marchal]

I'm going to follow Hispanic Slammer's advice.

I've found the Seafoam, and am ordering the gaskets.

I'll keep you guys updated

Frederic

[Frederic Marchal]

Update:

I'm preparing to purge the injection circuit with Seafoam, I'll let you know the results.

2 questions/comments:

1. When i turn on the key, I don't get any blinks. But I tried the self diagnosis by shorting the Service check connector, as indicated in Page 5-6 of manual.

All I got was the FI lamp blinking at 3 second intervals. I stopped counting at over 30 blinks with no sign of stopping. The manual stops at 20 blinks. I also performed the reset procedure then tried again - same result.

What am I doing wrong? The only difference is that the tank is removed from bike, so pump circuit is open. Lights are also disconnected.

2. Re: I tried the voltage test referenced for TPS, MAP sensor and IAT sendor. All specify a 5 volt reading on specified harness terminals. I couldn't find 5 volts in any combination.

But I did try resistance on the TPS and got a nice increasing resistance as I turned the throttle. I therefore assume the TPS is no longer the main suspect.

Any comments?

Frederic

[HispanicSlammer]

if its 3 seconds between blinks that is just one blink, and then cycling through with one blink again.

a .5 second pause is the count between blinks (blink .5 seconds blink = 2 )

a 1.3 pause then blink = 10 blinks (blink 1.3 seconds blink = 11 blinks)

3 seconds between blinks is a recycle of the diagnois so ( blink 3 seconds then blink = the same thing 1 blink repeting itself)

1 blink the code is a loose or poor connection on the map sensor, in the wire, or unhooked vacuum tube. The map sensor is right on the airbox right hand side.

[Frederic Marchal]

Revision to last update...

Re: my item #2: I had forgotten that the side stand must be down during these tests. I now have 4.93V readings.

Frederic

[scarygary]

Hi Frederic,

Any more follow up on the sputter problem. My VFR has developed the same symptoms and I am tempted to clean out the injectors. (88000 kms).

Thx. g

Revision to last update...

Re: my item #2: I had forgotten that the side stand must be down during these tests. I now have 4.93V readings.

Frederic