Titanium engine stumble and cough

[TrogloBiker]

Hey. My 2004 titanium has developed a cough. It occurs only when I'm cruising through town with a steady throttle between 2,000 and 2,800 rpm. It started a few months ago and has gotten a little worse. I looked for obvious signs and saw some extra soot around the right throttle body intake boot. I tightened the screws down and put new spark plugs (BPR6ES). Still does it. Runs down the highway perfectly, and pulls real strong, but as soon as I come down into town and run a steady speed it starts again. The cough is coming through the air cleaner. Are there any other obvious things to look for? Throttle position sensor? The air cleaner is KNN with some holes drilled in the plastic cover. Put 20,000 on the KNN with no trouble until recently. Fuel filter is fairly new, and I stay away from ethanol. (learned the hard way at about 10,000 miles) Any ideas would be appreciated.

[bigbikerrick]

 My Aluminum does the same thing, I have suspected the TPS, but have not done anything about it yet.  Rick
                                         
                                                                                      :pop

[guzzisteve]

Depending on miles, clean throttle bodies, set TPS base, sync throttle bodies & set air screw, set idle mixture.

[fotoguzzi]

can you get software on it ? might be a trim adjustment is in order..

[Chuck in Indiana]

Just for grins I would check for a vacuum leak around the rubbers that hold the throttle bodies on. They tend to crack where the clamp bites into them.

[menzies]

Just for grins I would check for a vacuum leak around the rubbers that hold the throttle bodies on. They tend to crack where the clamp bites into them.

What Chuck said, my 02 Special Sport was presenting the same symptoms, replaced the rubber boots on the injectors and all is good.

[fotoguzzi]

Just for grins I would check for a vacuum leak around the rubbers that hold the throttle bodies on. They tend to crack where the clamp bites into them.

spray something in the area and see if the idle increases?

[Orange Guzzi]

Take the tps off and pop the cap to see what is inside. It will pop right apart and go back together with out any issues.  I was surprised to see that mine was bad from the factory.  As you can see in the picture, the contacts are deformed.  This caused the tps to make contact in several locations at the same time. 

[TrogloBiker]

Thanks, I'll do that today. It's supposed to be almost 50 degrees here today.

[scra99tch]

Spray a little propane around intake rubbers (less messy than WD-40).  Check for soot around screws on manifold.  Had a casting flaw close to screw head that went straight into cylinder.

Other than that TPS adjustment and CO trim increase.

[Kiwi_Roy]

Poke a sewing pin through the wire going to pin 11 of the ECU (that is the slider of the TPS)
Measure the Voltage from the pin to chassis, it should ramp up smoothly from about 400 mV to around 4.5 Volts as you slowly open the throttle.

I have a short wire ending with a blue crimp connector tapped into the TPS slider wire, it makes it easier to do a throttle balance, the blue crimp
connector is just the right size for a meter probe.

[TrogloBiker]

Thanks for all of the suggestions. I did go out and spray starting fluid all around both throttle body boots while the bike was idling. No difference. When our 50mph winds die down I'll check it further.

[Tom]

Guzzi engines don't "cruise" well.  Raise your rpm's or drop a gear lower.  Usually 1st gear in town.   :+1 on the TPS may need the contacts cleaned.