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General Category => General Discussion => Topic started by: Irishflyer on June 08, 2026, 10:54:21 PM
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I have a 96 Cal 1100i, P8 ECU, that suddenly started running very rich, same ol story hates to run 3k and under, but runs awesome above 4k. Plugs were black, and wet. I have already done the following:
Valve adjustment
TPS adjustment, 150mv, 385mv idle
cylinders balanced
Air and oil temp sensors resistance measured, they are good, and the same.
The crank and pickup at the flywheel seemed to be clean.
New air filter, fuel filter (it was time anyway).
I am suspecting the MAP sensor. I am at 2800', and the starting voltage from a 4.8 reference voltage was 4.02v. I am thinking it should be a lower value? I tested it, applied vaccum and pressure. At 100 kpa, it was around 4.8, at much lower kpa it dipped down to around 1v or less. I am thinking if its starting at a higher voltage, it thinks at Im a lower altitude, and over fueling the bike. The trim screw in the ECU I think is correct. I had leaned it out idling and had given it enough to where it started to idle smooth. I guess the fuel pressure regulator could be giving her the beans as well.
Any thoughts?
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3000 RPM and lower would be the air bleed screws and idle mixture screw on ECU. Clean the air bleed screws & holes. I seen them get gooed up. set at 1/2- 3/4 open. Idle mix screw is clockwise is leaner & counter clock is richer.
I use a ColorTune to set idle mixture, that way I can see the flame color in head when I adjust it.
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(https://i.ibb.co/zWRmShvF/Screenshot-2026-06-09-083446.png) (https://ibb.co/zWRmShvF)
You need GuzziDiag to display all of the values.
The temp sensor in the head is a weak spot.
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(https://i.ibb.co/zWRmShvF/Screenshot-2026-06-09-083446.png) (https://ibb.co/zWRmShvF)
You need GuzziDiag to display all of the values.
The temp sensor in the head is a weak spot.
I tested the oil and air sensors with the engine cold, it was 26° C, resistance was around 2900 ohns. I'll try warming it up and retest.
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3000 RPM and lower would be the air bleed screws and idle mixture screw on ECU. Clean the air bleed screws & holes. I seen them get gooed up. set at 1/2- 3/4 open. Idle mix screw is clockwise is leaner & counter clock is richer.
I use a ColorTune to set idle mixture, that way I can see the flame color in head when I adjust it.
Good info to have. The screws presently are about 3/4 out; the problem was a sudden occurrence last fall as I was leaving a restaurant, started to stall, ran rough. I had suspected a TPS had gone bad, or a fuel filter except it ran so good above 4k I didn't think lack of fuel was the issue. I hadn't heard of a ColorTune, just looked it up. That is very cool!
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Further testing, still running way too rich.
Warmed bike up, seems to be getting worse.
Air and oil temp sensors are reading almost exactly what the chart calls for, tested without and with harness attached.
The baro sensor seemed to be working, and fairly close to my pressure close to my local airport.
I pulled the back cover off the ECU and found the center of the trim pot.
Spark plugs are black, sometimes even look a bit wet.
I'm down to weak coils, plug wires that are on their way out, or a fuel regulator that's giving it the beans flat out. I will be putting in new plugs again (these have 30 miles, if that, in them). Plugs are NGK.
The joy of ownership!..lol.
Did continuity tests with the wiring harness, checked for any bare wires.
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If you turn mix screw on ECU to the right it makes it leaner, do 1/8 turn at a time.
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If you turn mix screw on ECU to the right it makes it leaner, do 1/8 turn at a time.
It must be pretty sensitive, because at the halfway point you can smell how rich it is..lol.
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It is & it's not immediate, might take a minute to settle. Just what I have observed from mine.
Make sure throttle bodies are clean and air screws & holes are clean too. Seen them plug from goo & plugs go black.
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Well, got a curveball last night. Fuel pressure tested close to spec, so not over fueling. Frustrated, I decided to start over at the TPS, a new part btw. Removed linkage, backed the screw off, and got a surprise. It read 4.6v, and moving the throttle body linkage, it went OL and just bounced randomly. Changed DVM, same result. Retrieved old TPS and plugged it in, smooth from .005v to 4.7v or so. Reading a 4.6 at idle position would certainly cause a rich condition..lol. Anyway, the new part was from ebay, certainly cheaper than a Weber-Marelli PF09.
I have a question, would the next newest iteration of throttle bodies work with a P8? This is what I cherish about the Guzzi community, we just work around things..:-)
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Here ya go, better stuff
https://ca-cycleworks.com/EFI_c_14.html
I think it's a PF03
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Here ya go, better stuff
https://ca-cycleworks.com/EFI_c_14.html
I think it's a PF03
I went back and looked. I bought that exact TPS 08/25 from CA Cycleworks. I thought I had gotten it on ebay.
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Never got a bad one from there. You could go get a Harley part, they work.
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Well, trying to reuse the old TPS, and it I don't have enough adjustment in the slots to set it. You have to push it almost all the way to one end, and the adjustment is so fine, I was using a small screwdriver wedged in the slot and against the frame of the throttle body to make minute adjustments, it goes from .004 to .500, and trying to tighten the screws doesn't help.
UPDATE. I took the TPS apart, and one of the three fingers had gotten bent a little. Last year I had read the TPS get dirty, so drill a small hole and hit it with electrical cleaner. I think the top of the bit hit the inside arm, bending it. I cleaned it inside, straightened out the little arm, and now it's functioning like a normal TPS.
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Seems to be running normally now, though a bit lean, I will adjust the ECU in small increments. Well, let this be a lesson that new parts can go bad and really mess with your sanity.... :cheesy: