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Baro/MAP sensor voltage to altitude chart P8 ECU
Irishflyer:
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?
guzzisteve:
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.
Wayne Orwig:
You need GuzziDiag to display all of the values.
The temp sensor in the head is a weak spot.
Irishflyer:
--- Quote from: Wayne Orwig on June 09, 2026, 07:36:14 AM ---
You need GuzziDiag to display all of the values.
The temp sensor in the head is a weak spot.
--- End quote ---
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.
Irishflyer:
--- Quote from: guzzisteve on June 09, 2026, 07:33:53 AM ---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.
--- End quote ---
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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