I have been enjoying the "new to me, but with 46K miles" 907, but I have one issue:

Once the bike warms up (after at least 10 miles and up to operating temps in the summer) I do get an occasional stumble. This happens on acceleration, at any rpm, but very infrequently. The bike bucks and stumbles, and it does not want to accelerate. It feels like it is starved for fuel or spark. When this happens it also wants to die at idle. I have to keep it running by goosing the throttle. It normally clears up after a few seconds, and everything is back to normal. If I restart the bike, everything is fine, too. This situation is truly intermittent.
Where should I start the chase? Does the stumble and rough idle when warm mean that I should look at particular grounds, relays, or sensors? While the bike is high mileage the top end was done and a lot of parts have been renewed and swapped. The condition is intermittent enough, so I am ruling out fuel filter, air filter, plugs, and coils. Maybe a relay or sensor is heating up and causing an intermittent fault?

regards
luke

when that happens and you open the fuel cap does anything change? If so the tank breather hose might be clogged.

G.

Thanks. I will check to see if opening the cap evens out the idle. Or maybe see if the tube is crimped. Last time it happened I was just trying to clear the intersection!

could also be an electrical connection, I had a defective key switch on a P750 with Digiplex and every now and then the switch would cut off and send the digiplex into "crazy mode" (ultimately it died)

I would check all connections and move all wiring around the steering (sometimes they break) you might be lucky and find the issue straight away.

AH yes, also, try also moving the pickup cable, with the age thet become hard and tend to crack causing issues; it is an easy fix, it is a common Fiat spare part.

as you mention it angelix I received the following pic from a forum member a few days ago.
This is the strain-relief below the ignition switch. It had almost completely cut through one wire. A hard thing to find as when the strain-relief is closed/pressed together you won`t even see the damage.

+1 on the ignition switch and its wiring


also with that mileage I'd check the in tank fuel filter and go over the entire electrical system.grounds and connectors. A clogged in tank filter can cause all kinds of electrical issues due to the fuel pump working extra hard which will make it overheat and draw more current which in turn can overheat the stator and its wiring melting connectors all over the wiring harness


A clogged fuel filter is probably the root cause of many electrical issues on these bikes and the single most overlooked issue when chasing electrical gremlins,especially charging system problems.

Thank you, gents. I have formed my line of attack. I also have a new ECU that the previous owner has provided, so I will try this, as well. New FI and ignition relays are on order, too, since they are cheap. I also have an extra in-line fuel filter and will check the screen in the tank. I can totally see how a straining fuel pump could be causing this issue (pump itself being bad or an obstruction). I have looked at the ignition cables, and nothing looks suspect thus far, and the fuel breather is not crimped, but I only had 2 hrs last time, so I will poke around for bad grounds and post up when this gets resolved.


Thanks again

In general the only thing goes bad with these ECU's is the fuel pump circuit. It often is spiked during misguided trouble shooting at the relays(2). The symptom here is no 2 sec pump initialization when the key is turned on
simple fix is ground the terminal for the pump at the ECU, more involved repair is fix the circuit and replace the diode on the ECU board with one from Newark electronics supply. The expensive repair is replace the ECU with a P8 and get someone to send you a remapped chip or bin file and upload it yourself to the chip utilizing the GuzziDiag IAW program which does have many advantages to the P7 as Ducati enabled it.

I looked around on this board and I found some information about the relays (fuel pump and ignition). Alfa Romeo also seems to be using the same type of relay in the 164. The ones from a later 916 Ducati appear to fit, but are unfused. Ducati has nothing in stock, of course.
I will try the route of getting one from the auto parts store (blades and ratings), but has someone in the meantime found a source for the exact relay?

Here is one that I found on ebay, but the last series of numbers does not match

12V 20A B047 E 232006 BLTRON
should be:
12V B047 2335

thank you. I will start with the Alfa Romeo dealers tomorrow. Fortunately...I had owned something like 8 Alfas in a row, so I know where they are all hiding.

i think this one might be more like it:
http://www.ebay.com/itm/Italamec-Relay- ... 28&vxp=mtr

at least it has 5 prongs and the description reads:

Vehicle Model: Maserati, FIAT, Alfa Romeo, etc..

Manufacturer: Italamec

Description: 12V 20A , marked 7k on side of grey relay.

Also marked: A727 510 7686773

Number of pins: 5

Color: Grey

Country of Mfg: Italy

just following up, just in case anyone in the same situation can benefit in the future. My issue was not electric/electronic. It turned out that a compression / leakdown on one of the cylinders came back bad. The exhaust valves were not sealing. I did not want to learn this one on the first try in my own garage, so I had outsourced the top end rebuild to a local shop. Bike runs nice now! No more stumble and dying while hot. Did the belts, while in there.

I do have a high temp registering on the gauge, but this could be inaccuracy of the instruments. It is one (or one and a half) hash mark away from 250, although the needle is pretty thick and the "tolerable max" fat line is pretty close to the end. I need to listen for the electric fan turning on. Bike did not exhibit any overheating signs.

found an unplugged 3 prong plastic connector poking around tonite. The wires on one end are black and violet/black. According to the wiring diagram in the owner's manaul...this is the electrical connection for the fan. I will test ride tomorrow, but I think this was my issue.
If it is not one thing, it is another. I hope she forgives me for running her a little hot for a few stoplights.