Stelvio 8v stalling when idling

[Robmason]

The Stelvio 8v power unit in my Triking runs well as soon as it's on the move, the engine runs smoothly, no surging, dropping, nothing like that. Basically, the car pulls very well once on the go.

However, as soon as the rev's drop to below about 1800 rpm (for example when stopping or when manoeuvring into a parking spot), the car will sometimes stall, or idle very rough, other times she'll idle fine. Very intermittent behaviour.

The main problem is that the car won't idle constantly (cold or hot), the engine rev's surges up and down (between 1200 and 1600 rpm), sometimes it drops (misfires), I can both hear and feel this.

It’s a low mileage “re-conditioned” power unit (done by Triking) and has covered 800 miles since I bought the car new in June.

Does anyone have any suggestions / solutions before I start to fiddle with the car.

Many thanks

Rob Mason

[Lowpass]

Don't think I can provide any specific assistance as I suspect your engine management system will be different than my 1997 8v Centauro. I was able to find some very useful information on the WildGuzzi Forum and Centauro Owners Group Forum.

My engine exhibited symptoms somewhat similar but milder to what you describe, but as I said, mine will most certainly have a different (and cruder system than yours). My engine would idle fine at the specified 1200RPM but would periodically stall after extended idle. It also had a slight stumble just off or idle and would sometimes backfire and stall on take off if I started clutch engagement in the stumble area. I was able to eliminate my issues by adjustment of the Throttle Position Potentiometer, idle stop and my choke adjustment. I think the major culprit was the choke as it was adjusted such that it was always on even with the knob pushed all the way in. This caused the TPS voltage to be off as well as the idle stop. Once I got the choke adjusted so it had no influence on throttle position when pushed in, I was able to adjust the idle stop to get 1200 rpm and the TPS for the correct voltage at idle, and all is good. May not be your issue, but worth a look. You will want a Stelvio workshop manual if you don't already have one. My Centauro manual has been very helpful, though it can sometimes be a bit confusing with the translation from Italian to English. I assume your engine management computer isn't throwing any codes?

[MarkG]

Rob,
My T4 also has the Stelvio 8v engine, as does John T , JT Design, who has worked on the engine loom and the mapping for type 4s. John's later maps worked best for me. CO Trim also needs to be set correctly. Mapping uses GuzziDiag free software. Maybe give me a call?
Mark

[Lowpass]

From the Guzzitech Forum. Looks familiar....
https://www.guzzitech.com/forums/thread ... ues.19986/

[guzzitrike]

Guzzidiag and Beetle maps worked for me on my Stelvio, whether this can be utilised on a triking I am not sure but it will likely be better than the standard Guzzi set up which is there to satisfy EU emission controls.

[jtdesign]

Rob,
the irregular idle, especially if intermittent is likely to be the idle control valve sticking (the valve has a 4-way connector and sits in between the two throttle bodies). This is controlled from the ECU and is adjusted to give a 1200rpm idle once the engine is warm. It bypasses the throttle buterflies to provide the correct amount of air to the engine, the ECU itself controls the fuel, so if the valve does not position correctly the mixture will be wrong.
On the Stelvio bike the idle valve gets its air from the air box which also receives engine vent gasses (and oil) so the valve tends to get gummed up and stick. A bit of judicious application of carb cleaner to the valve can be helpful. There are two types of valve fitted, but I don't think either of them can be dismantled, so claning has to be done on what can be reached through the air ports.

I have prepared several maps for the 8V engine which differ from the Guzzi maps (and indeed the Beetle maps) because the exhaust arrangement on the Triking is so different from the donor bike. You will need Guzzidiag and a suitable OBD2/USB adaptor to re-program the ECU but I am quite happy to send you maps if you want - send me a PM with a contact number so we can discuss. As MarkG states, the CO trim adjustment is important but since your problem is intermittent I would not suspect that this is the main problem.

John.

[Robmason]

Thanks everyone for the comments. The issue (thanks to Mark and Alan at Triking for the diagnosis) was more straightforward than thought, and was a split in the Stelvio RH spark plug cap which is made from rubber. It was the original made in 2009. New 90 degree caps and integrated leads can't be used as they are not long enough (the leads that is) so the originals had longer leads fitted.
Triking supplied new straight caps/leads. Now fitted, the idle speed is the normal 1100 rpm.
Thanks again for the ideas and comments.
Rob