is my TPS dead or dying?

Technical Big Block Tonti and Loop Frame models
1

Investing in GuzziDiag software and hardware, I attempted to tune my 2001 California Special, (Power Commander had died on me some years before) and I felt performance was deteriorating after 21 years of just general cleaning and rigorous maintenance. I found that the TB’s had some serious play in the L/H TB. New bushes and seals fitted to sonically cleaned TB’s, injectors checked and cleaned, I had another go.

Although I initially struggled to get the idle down to 1100RPM, (I noted that the CO trimm was originally set at -35, I changed this to 0, don’t ask me why) after multiple attempts at getting 1100RPM I reset the CO Trimm to the original -35. Finally, the Cali seemed to be running much better, more responsive and seemed much happier!

After being laid up over the cold and dreary winter months, I finally sprang into action on a warm pre-spring day and tried to start my 2001 California Special, ha, flat battery.

Battery fully charged and I found it very difficult to start (degraded fuel, I thought). Eventually she fired up, popping through the exhausts and spitting back through throttle bodies (TB’s). I should imagine the neighbours thought there was a shoot-out taking place in our little close. Changing the spark plugs made no difference. Very weak fuel mixture, me thinks! Clean fuel and a quality TB/injector cleaner made no difference.

After rereading the TB setup procedure and checking that all readings were within the recommended tolerances, although starting and running better, the Cali was still spitting back through the TB’s at low RPM and popping on the overrun. I had a spare TPS, so sprayed this and the original with contact cleaner and fitted the spare TPS, I found a slight overall improvement after every attempt at eliminating the spitting back and jerky acceleration and cruising at low RPM, but all to no avail.

I eventually disconnected all electrical plugs, relays and fuses and sprayed them with a cleaner, the oil temperature sensor was quite corroded and some of the relay blades were slightly corroded.

Is a faulty TPS causing these problems?

With the original TPS fitted and following the factory procedure for setting the TB’s from scratch, with a slight change.

  1. Set disconnected L/H TB to 150mV.

  2. Adjusted TB idle screw to read 520mV.

  3. I then increased the L/H TB reading to 620mV by releasing and moving the TPS.

I found the running improved, but this didn’t eliminate the poor running experienced earlier.

Repeating number three above I released and moved the TPS to read 720mV.

This setting eliminated the poor running experienced prior to this, However, I need to run the Cali much further and longer to ascertain that other important factors are not adversely affected.

Are the above symptoms indicative of a faulty TPS?

What are the symptoms of a faulty or broken TPS?

Any comments or suggestions that will lead to the elimination of these problems and allow me to revert to the factory settings will be much appreciated.

2

Hi!

With the greatest respect, i have just read your ‘set up’ procedure and it doesn’t really make any sense. Below is a ‘copy and paste’ from a previous thread.

A couple of thoughts!

You are disconnecting the Lefthand Link Bar when setting the base TPS setting?

I do mine useing a Multimeter and a Breakout Lead.

Let me try and run thru this step by step!

Disconnect L/H Link Bar and back out L/H ‘sacred screw’ so that it does not touch the Adjuster plate and the butterfly is 0 deg (fully Closed)

Rotate the TPS itself until you achieve 150Mv then useing the L/H ‘sacred screw’ winde it in until you achieve 176Mv (butterfly slightly open) + or - about 15Mv on both

Reconnect Link Bar. Make sure Byepass Screws are 1/2 turn out. Run engine upto temperature. Balance idle using R/H sacred screw. Run engine upto 2500/3000RPM to balance fast running using Adjuster in the middle of the Link Bars (Sometimes on the L/H Throttle Body)

That should give you the correct Idle and CO. If the CO is slightly out you can adjust using Byepass Screws, though you shouldn’t have to! Final setting of Idle, use the Idle Adjuster screw

I hope that all make sense, Nik

It may just be the way i am reading it!

You should get a smooth linear increase in voltage from the TPS as you adjust it. If not, its probably toast!

Good luck, Nik

3

Hi, Nik. Thank you for the reply. Should have mentioned that I use this procedure ( Brad The Bike Boy: Throttle Position Sensor setting procedure for Moto Guzzi California and Bellagio ) for setting the TPS and tuning with GuzziDiag. As mentioned, unless I reset the TPS higher than the recommended 520mV, the Cali does not run well at all.

The TPS mV seem to advance slowly, not erratically, as the throttle is turned. I found some info online regarding checking the resistance of the TPS. I’m going to try and find it again, to see if this helps.

I don’t want to pay 600 odd squid for a new TPS, in the same vein I don’t want to buy parts from PRC or USA, either.

Regards

Mog

4

Hi Mog

Just read thru ‘Brad The Bike Boy’ In Section 9, he states that the TPS setting should be 486 - 528mV, which is, i believe incorrect. It should be 176mV once you have set the TPS base setting at 150mV and then screwed in the ‘Sacred Screw’

I will double check this on monday when i’m back in the shop but the system i use is from ‘Guzzioligy’ because i found over time that the Guzzidiag doesn’t really work with this particular problem and as i mentioned earlier i alway use a Multimeter and a Breakout Lead with , assuming everything else is correct, very good results.

From what you said about your TPS in your reply, it sounds as though its good, if the mV’s progress smoothly as the Throttle is opened.

Nik

1 Like
5

A minor point: IIRC you may get a spit and misfire at around 2500rpm. It’s a hole in the rev range put there to pass noise regs. This is something that I’ve read but not experienced, but I’m pretty sure that a PO of my 1997 Cali 1100ie did experience it as when I opened up the ECU I found the bike had been chipped with one of the (then) recommended German fixes/upgrades.

6

Not applicable to my problem, DiaGThank you all the same.

1 Like
7

This wouldn’t work in my case, Nik.

As I said I have to set the TB idle opening At 720mV to eliminate the poor running.

8

Just a few thoughts from my own journey with this.

Have you eliminated all potential contributing factors? Everything adds up or at least it did in my case. I thought my issue was the TPS but found many other things along the way. The TPS is a base setting for the ECU fuelling maps. But fuel pressure, fuel supply etc can all contribute to the issue. Also valve clearances?

I had both of my injectors out and thought they were both ok. But on very close inspection (injector pressurised with fuel on the bench and a magnifying glass) I found that one of them was leaking very slowly. Also when I dug deeper I found the tank was absolutely full of crap, the pump was partially blocked, the main filter had never been changed, and the fuel pressure regulator was inconsistent and needed replacing.

I haven’t checked it yet but I also need to look at the temperature sensor because the feedback from that will affect fuelling. What I’m trying to get at is that I think it can be much more than just throttle body and injectors. Everything affects everything.

Lastly I found it virtually impossible to use guzzy diag to read the bass setting for the TPS. Speaking to Mark at beetle maps he said always do the base setting using multimeter. I ended up replacing mine with one from Cali works.

9

Hi Nik. Just reading through your description there. I’m not sure this applies to a 2001 Cali? All of the adjustments are on the left hand throttle body on mine. The right hand throttle body has the factory set screw. As in the one you shouldn’t touch.

10

There are differences from the early 1100i and the later 1100i / early EV. The later EV is different again, but the setting up is basically the same. The 1100i has horizontal Bypass Screws whereas the EV has Vertical, as an example, but not all of them. Typical Guzzi!

As for the ‘Sacred Screws’, if you have a copy of Guzzioligy, just follow Dave Richardson’s (or mine) instructions and you will realise there’s nothing really sacred about them.