Wildguzzi.com
General Category => General Discussion => Topic started by: Moguedfu on June 06, 2026, 03:50:25 PM
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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.
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Do some searching here. There was a company called I think California cycle that sold the right TPS for about $90. Best to start with new. FWIW my 01 would only run right at +30. At +27 it was lean. Setting to 540 should work fine. They fail because the gas drips into them and dry up. It should have been placed on top of the throttle body. Did you take the injectors to a diesel shop for a real cleaning? Have you replaced the fuel filter and cleaned the tiny screen in the shutoff valve?
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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 do not understand your step #3.
You set the TPS baseline at 150mv with the throttle plate closed in step #1, then at step #3 you set the TPS higher (richer). And at the same time, you set the CO trim leaner.
So do you want leaner, or richer? Why not leave the TPS at the correct setting, then just tweak the CO trim if needed?
What all the trouble you are having, I would replace the TPS. But it doesn't sound like a typical TPS issue.
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Follow this guide. It works:
https://archive.guzzitech.com/EVTuneup-Jeff_B.html
When you do the 150mv setting for the TPS, the tie rod between the TB's is disconnected on the LH TB. Then the idle screw is fully back off on the LH and RH TB. Then the TPS is set to about 150mv. Then use the idle screw to bring the volts up to about 525mv.
Now read the guide and remember to look at the specifics for what I just wrote.
TB balance is also something that needs to be done.
Tom
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Wanye is correct.
Loosen torx screws on TPS with everything off and backed out (linkages, and allen set screw).
Twist TPS until 150mv, using a voltmeter, not the software. Make sure voltmeter is on the correct leads.
Tighten torx screws on TPS now, with allen screw aim for the .520mV. That is the baseline check. Once everything is hooked back up it'll change the voltages I believe.