99 Drifter running poorly at low speeds

[cptarmy2002]

Well turns out I did everything right in the Throttle Body install you will still need to adjust the TPS. Turns out that although they are set at the factory, you must go through the entire resetting process in order to make the bike run right.

I tried to adjust it, but realized that it was a bridge to far for me to get to that back bolt with the T25 socket so I took it to my local private shop (not a dealer) and they fixed it all for $125.00 That was worth it for me, so instead of being $800 for a new TPS installed it was ~$200. I figure that was a good deal considering and now I'll get another 35K out of my bike...

Thanks for the help!

[cptarmy2002]

Exactly the one that I was referring to...I have the one from the fuel pressure regulator and the throttle body connected correctly...I will plug the other hose and see what happens...thanks for the quick response!!!

[Troll]

The fuel pressure regulator has a T fitting. one side goes to the port on the throttle body, the other goes to the pulse air control valve. If that hose were to be sealed off, the pulse air system would be effectively disabled. This is basically the same as the "marbleing" people do to stop the exhaust popping. Plug this hose and see what happens. If the vacuum signal is low going to the regulator it will make the system rich, like you were pulling up a steep hill. Sealing off the hose will keep manifold vacuum on the regulator and should restore a proper mixture. As always...let us know what's happening.

[cptarmy2002]

I've been thinking about this one for a while. You have a 13-14 year old motorcycle. Fuel lines and vacuum hoses deteriorate on newer vehicles than yours. If this happened suddenly I would suspect a vacuum leak. Under the tank is a rat's nest of both wires and hoses...and mice have been known to eat them...but my first thought would be to check out the fuel pressure regulator. I've replaced a lot of these over the years on cars, primarily due to the effects of alcohol. There is a single vacuum line running to it, and if the line leaks, or the diaphragm were to rupture, the engine will run VERY rich. There would be no code, nor would the ECU even notice the engine was running rich. The system is called open loop, and there is no feedback to the computer to tell it what's going on, outside of voltages from the sensors indicating engine temp, load and throttle position. There is a plastic T fitting that runs to the air switching valve, which shares the manifold signal. If the hose leaks, or is disconnected, the regulator will deliver full fuel pump pressure to the injectors...just a thought.

Help - I've been off and on the board for the last two years and just ran across a problem that I can't figure out...the Throttle Position Sensor went bad so I sourced a replacement Throttle Body and installed it all over the last 2 days. Bike starts but won't idle very well and there is faint black smoke coming out of the exhaust (running rich). One thing that I know I didn't get right was from the picture Troll posted in this thread (hope I liked it correctly above).

I broke the old T-Fitting Part #92005 when I took off the old Throttle Body, but the replacement came with the full T-section on it (everything from the throttle body T-Fitting and both tubes), so I installed the left side one to the fuel pressure regulator side, But I have no idea nor can I see where the throttle boost tube goes (Part #92191)? I can't see any other fittings or places for me to put it nor the remnant of the old hose hooked up somewhere else?

If this helps, I've done the following Mods - V&H StraighT shots w/ PCIII mapped to it, K&N air filter and I did the cam chain extenders. Bike has 36K miles and has run perfectly for the last 2 years when I got it at 22K.

Any Advice?

[Troll]

Guilty conscience? I never even gave you a thought.

[CDNRatMan]

  Sir Troll, I take exception to your statment.....I did nothing on this guy's bike.....

is a rat's nest of

so please rephrase your response.......lol......

[Hammer]

No lighting changes.  No Power Commander.  Only does it when I have done quite a few miles.  After it cools off it runs fine.  Runs just fine under throttle on the freeway but not at a low constant throttle.

[Troll]

Just a stray thought...(like stray voltage), but do you have a power commander or other fuel tuning device installed? These have been known to really mess things up at times...

[chief]

Have you added any lighting or increased the wattage on the headlight or both?

[Hammer]

I will check that out this week.  I have no codes, so that might be a solution.  It runs just fine under load but not at a slower sustained speed.

[Troll]

  I've been thinking about this one for a while. You have a 13-14 year old motorcycle. Fuel lines and vacuum hoses deteriorate on newer vehicles than yours. If this happened suddenly I would suspect a vacuum leak. Under the tank is a rat's nest of both wires and hoses...and mice have been known to eat them...but my first thought would be to check out the fuel pressure regulator. I've replaced a lot of these over the years on cars, primarily due to the effects of alcohol. There is a single vacuum line running to it, and if the line leaks, or the diaphragm were to rupture, the engine will run VERY rich. There would be no code, nor would the ECU even notice the engine was running rich. The system is called open loop, and there is no feedback to the computer to tell it what's going on, outside of voltages from the sensors indicating engine temp, load and throttle position. There is a plastic T fitting that runs to the air switching valve, which shares the manifold signal. If the hose leaks, or is disconnected, the regulator will deliver full fuel pump pressure to the injectors...just a thought.

[chief]

Ok... start simple. No modifications to the bike just prior to poor performance I presume.

1. Check the position of the choke knob... not really a choke, but make sure its all the way in.
2. a low fast idle speed can be a problem.. lots of people adjust the fast idle in an attempt to make the drifter idle like a harley.
3. improperly set idle speed.
4. Make sure nothing is impeding the throttle body operation
5. Make sure the air filter is clean and check the duct work if you haven't modified the air box.
6. Low battery voltage can cause problems at low speed so verify you have a healthy battery.
6. Spark plug/wire inspection and spark test
7. Could be one of the sensors or injectors etc... so run an ECU fault test.

[Hammer]

I have already done that.  Just started doing in one day about a month ago.

[chief]

Run a couple of tanks of injector cleaner through it, see if that helps... start simple.

[Hammer]

I have a 99 1500 Drifter.  Have had it since 2001.  It just started running badly at slow speeds  (20 to 50mph).  Feels like it is trying to cut off but if I give it throttle it goes well.  Runs just fine on the freeway when you have to keep throttle on.  Any suggestions?