Need throttle position sensor!

[kecup]

Hi everyone, it seems the TPS on my 97 1100 Sport-i has failed, after an unnamed local guzzi shop performed a top end rebuild which included TPS repositioning and cleaning (so I was told). The bike never run proper after the service so after putting some 50miles only in more then a year I decided to investigate. No matter on what position the TPS is the voltage output is always 5V, never the .140V recommended for the idle position, or any other number. It appears I need a new TPS, checked MGCycle but no success. Where could I get one? I am in Los Angeles but will never deal with MG Classics again. I can do with used TPS, does not need new one. My Sporti has the TPS mounted at the top of throttle body.

 

Pavel

[docc]

In October 2008 I got my replacement TPS from Harley-Davidson PN 27271-95 US$44.63

 

Plug (set) and play!

[Cliff]

The assumption is that you are measuring it correctly. If it was giving 5V I would say it would run a lot less than proper. It would probably not start if that was the case.

 

Just think, if the ECU saw 5V, it would think you had full throttle and fuel it accordingly. I'd be very suprised if it would run at all.

 

One of the 3 wires going to the TPS is 5V, one is ground and the other is the signal.

[kecup]

The assumption is that you are measuring it correctly. If it was giving 5V I would say it would run a lot less than proper. It would probably not start if that was the case.

 

Just think, if the ECU saw 5V, it would think you had full throttle and fuel it accordingly. I'd be very suprised if it would run at all.

 

One of the 3 wires going to the TPS is 5V, one is ground and the other is the signal.

 

Fuel actually seeps from the intake after the bike runs on idle - I am assuming the fueling is constantly in the mode "throttle fully opened". 5V is what goes to the TPS. My experience is the following (I might be wrong - my mechanical knowledge is next to none):

1. After the service at MG Classics the bike run, with poor idle and with a nasty habit of RPM hanging after one closed the throttle (by this I mean exactly that after closing the throttle, the engine RPM remained at 3-4th. for some 3sec. before going down slowly). Bike needed opened throttle to start.

2. I called back the shop complaining about poor idle (half of the cases the bike died in traffic after one closed the throttle), and was told by the owner that I should always hold the throttle opened a bit:)

3. I decided to increase the throttle RPM by turning the screws on the throttle body linkage. This allowed more air into the intake on idle, via opening the butterflies a bit. Bike had reliable idle now but developed a very dangerous habit - when hot in traffic, with CLOSED throttle, the RPM would steadily rise all the way to 6th., no going down, one always had to kill the engine to gain control.

 

So I think the excess fueling (if this is the case - we will have to check with new TPS) on idle was manageable at the expense of the full closure of the throttle butterflies (and resulting poor idle). When I set the idle higher by opening the throttle butterflies a bit (via screws on the linkage) - air was allowed into the intake and mixed with a lot of fuel made the engine run independent of the throttle. By carefully tuning the throttle bodies one can find a balance between the two - bike has poor but some idle, and the uncontrolled RPM rising is more or less manageable. One puts it totally out of control when trying to increase the idle by allowing more air into the engine. I should mention that I never had any problems with the bike before the service and I got the bike from them that is a plain danger to drive.

 

Pavel

[kecup]

In October 2008 I got my replacement TPS from Harley-Davidson PN 27271-95 US$44.63

 

Plug (set) and play!

 

Thanks a lot - will do that.

 

Pavel

[Wits]

Hi Pavel

Has the TPS been taken out of the throttle body by the guzzi shop? Could have been put back into the body incorrectly.

As the voltage never drops below 5V.

Never having taken the TPS out of my 1100 sport, that only solution I can think.

Wits

Shropshire UK

[pasrider]

If you're in the greater LA area, I'd recomment RTL Moto in Huntington Beach My link. Sean used to service my Cafe Sport when he worked at MG Classics; he was the one who did all the work on the newer models, and left MGC early this year.

[emry]

I'm with Cliff, you measured the voltage on the wrong wire. 5 volts is the supply voltage. If you read that on the sensor wire (what is read by the ECU) it would think you were beyond wide open all the time. I also doubt it would run for long, if at all. Think fouled plugs.

 

If the TPS is really "shorted" you will have 2 wires with 5volts and the third should be the ground, otherwise measure again.

 

I have seen TPS short high but never past 4.5 volts or so, if the ground wire has resistance it will push the TPS signal high, but never to the full 5volts.

 

Why didn't you take the bike back and have them take it for a test ride.

 

Normally a rich mixture will cause idle speeds to drop quickly, sometimes even die on closed throttle. Lean mixtures (think air leak) will cause the idle to hang high durinng closed throttle, which will get worse as the bike get even hotter from the lean mixture.

[Cliff]

It sounds like a few tweaks have crept in. Creeping to 6th with idle throttle. Wow.

 

You should go back and do the TPS calibration from scratch. Make sure the air bleed screws are set. I use 2 turns out.

Set the idle to 1200 when warm. Anything lower and you risk the stalls.

[Kiwi_Roy]

The TPS has 5 Volts on one end, and 0 Volts on the other.

The slider slides from the 0 volt end towards the 5 Volt end as you increase the throttle setting.

when it's set up correctly the slider is a little way from the 0 end (140mV) with the throttle closed.

At full throttle it's about 4.5 Volts.

 

The only way the slider will measure 5 Volts is if it goes open circuit or the ground wire is open

[gstallons]

Pavel, do you know how to use an analog or digital volt/ohmeter ?

[Kiwi_Roy]

Here's how you can check it's connected right (assuming you have the same ECU)

Unplug the connector from ECU and measure the resistance between the different

sockets, you need a small wire or pin for this.

Note 2 checks that each end of the TPS is connected (not open circuted).

Not all TPSs are the same resistance, that doesn't matter, it will give the same

Voltage at any given throttle opening.

Note 3 checks that the slider is connected and traveling from end to end, this

should be a smooth transition from low to high resistance as you open the throttle.

Note 4 just checks it from the other end, this time it goes from high to low Ohms

 

ECU Test Points.pdf

 

Update, I just changed the drawing

[kecup]

Hi Pavel

Has the TPS been taken out of the throttle body by the guzzi shop? Could have been put back into the body incorrectly.

As the voltage never drops below 5V.

Never having taken the TPS out of my 1100 sport, that only solution I can think.

Wits

Shropshire UK

 

Do not know, they said they've cleaned and repositioned it - assuming you have to take it out for cleaning.

[kecup]

I'm with Cliff, you measured the voltage on the wrong wire. 5 volts is the supply voltage. If you read that on the sensor wire (what is read by the ECU) it would think you were beyond wide open all the time. I also doubt it would run for long, if at all. Think fouled plugs.

 

If the TPS is really "shorted" you will have 2 wires with 5volts and the third should be the ground, otherwise measure again.

 

I have seen TPS short high but never past 4.5 volts or so, if the ground wire has resistance it will push the TPS signal high, but never to the full 5volts.

 

Why didn't you take the bike back and have them take it for a test ride.

 

Normally a rich mixture will cause idle speeds to drop quickly, sometimes even die on closed throttle. Lean mixtures (think air leak) will cause the idle to hang high durinng closed throttle, which will get worse as the bike get even hotter from the lean mixture.

 

We measured the voltage for whole afternoon, all possible combinations among all the three wires, TPS in place, TPS taken out of the TB but connected (in this case the different positions made by rotating the slider manually). We used digital voltmeter. Results: two wires with 5V regardless of what we did with TPS, one wire with nothing.

 

I did not take the bike back because was leaving the country for three months, have other bikes which I ride instead and have more important things to do on Sat morning. Was also extremely angry with other aspects of this service (like brand new paintjob mysteriously scratched on two places while the bike was at the shop, cylinder oil leaks and so - just did not want to argue with people - one reason for going to this shop was their reputation - some of a cold shower to my experience:) But that's okay.

 

If there is an airleak why the problems disappear completely (together with idle:) when the throttle butterflies are set fully closed at idle?

 

But anyway - will have the new TPS for weekend - hopefully we shall see the light at the and of the tunnel:)

 

Really appreciate the advices.

 

Pavel

[Kiwi_Roy]

 

Do not know, they said they've cleaned and repositioned it - assuming you have to take it out for cleaning.

 

The TPS is a very simple device, just like the volume control in a radio.

You may be measuring the voltage on the wrong wire

One is allways +5, another is allways zero, the third wire Voltage varies in between, with the throttle opening.

If you look at the ECU plug the wire going to pin 11 is the one to monitor, slice a little insulation off it and

measure from there to ground. Another way is to drive a dress pin thru the wire and connect your meter to that