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Discussion Starter #1
I'm troubleshooting an unstable idle issue on my 2002 900 Sport. LT Snyder 3rd edition pp 146-147 recommends pulling the ECU wiring harness, attaching leads to pins 11 and 22 on the harness, then turning the ignition key on. If TPS is spot on you should get a reading of 150 millivolts. Seems easy enough.

My problem is that the reading I get is zeros and yes I know where the millivolt setting is. I've attached pictures of my Weber-Marelli 1.5 ECU and the wiring harness pinouts with my leads inserted into pins 11 and 22. Anyone have an idea on this?
ECU.jpg
pins 11 and 22.jpg
 

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lol. ya goose.

you need to backprobe the ecu connector with it connected to the ecu. the supply voltage to the tps comes from the ecu, so with the ecu unplugged there is no voltage in any of those wires.

or you can backprobe the tps connector. i think it's the outer two wires on one of them. one is 5v constant, one earth and the other the variant output. the 150mv refers to the base setting with the throttle blades fully closed.

this may explain the steps better. or just confuse you more.

 

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I use dressmaker pins when i backprobe electrical connectors, the type with big coloured plastic balls on the end so i can use red for + etc. they're fine enough to not damage the connection inside the plug case too
 

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Discussion Starter #5
A careful examination finds markings on the wiring plug that connects to the ECU. Those markings are located on the back or outer side of the plug and allow you to find pins 11 and 22 (specific to my Marelli 1.5 unit). I inserted sewing needles into the appropriate wires and checked millivolts as per Snyder. My readings were way off. I chipped the yellow paint off the screws at the TPS and made the adjustment there followed by the idle stop screw adjustment as per Snyder.

Result: total success in the form of a stable idle (1500 rpm in my case). I'm not sure what a dealer charges but this fix can be done for the cost of the Snyder manual, hand tools and a voltmeter.
 

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Discussion Starter #7
My understanding it it takes special equipment or software to adjust the idle speed. I'd love to her otherwise though. We're talking about a 2002 900 Sport ie
 

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you need a diagnostic tool to adjust the mixture, but you also need a gas analyser to see what it is. you can do it somewhat by feel, and if it's way wrong it's somewhat obvious. get the guzzidiag / iawdiag software and a cable from lonelec.

the actual idle speed is done with the air bleeds.

did you go through the link i posted? it's all in there.

loose closing clearances can make it idle poorly too.
 

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Yeah 1500rpm is too high.
This is some of the reason for the cost of fuel injection setup being high as it is a cascade of adjustments.
adjust sync= changes TPS
Adjust idle stop screw= changes TPS
TPS= changes fueling
No way to understand what the air fuel is = throwing darts in the dark.

It is not hard to do just follow the steps but it can be a number of steps to get it as it should be. Some are simply happy with it not how it should be and that is fine too, poor idle at 1100 or great idle at 1500 if either makes you happy you are done but know that neither are correct. The cost of the tools to do the job right is the price to get it as it should be, if you are not willing or able to spend the money and time then most of the time there has to be a compromise somewhere. Nothing wrong with that as we make choices all the time, pick you battles.

Just attaching all the "stuff" to set up fuel injection can take between 1/2-1 hour depending on model so that should let you know it is neither quick nor easy to do some times. Every time i hook up to a carbureted bike I stare at it for a few moments thinking I must be missing something as it is too quick and easy in comparison. Don't rip off the Efi just yet though the carbs have their own issues. Never fear you are getting closer with every new tool and job completed so given enough time you will figure it out.
 

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To simplify reading TPS voltage on my 916, I opened the connector and soldered in 2 wires to the relevant pins on the ECU connector and have a terminal block connected to a short lead (by the diag plug).

Makes connecting a voltmeter a doddle, meaning I don't need 2 sets of hands whilst adjusting TPS settings.

 

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Discussion Starter #11
Thanks again for the tips. It's actually been too cold here in Maryland for a proper test ride. I suspect the 1500 rpm idle is going to come down a little once the engine gets hot. It's sitting on 1500 very quickly after a cold start and is stable there.

I have heard reference to the Guzzi software but haven't digested a good article on how it works yet. That'll be the next step if anything is subpar on my next test ride.
 
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