Stalling Gremlins are back

[jfremder]

I'm beyond frustrated with a nagging problem on my 55k mi. '04 R1150RT.

After a hot restart, subsequent to a 5+ minute heat soak, my RT starts and idles perfectly. About 10-20 seconds later, the idle speed drops 300-400 rpm, and the engine stumbles, coughs and sputters. Most of the time it will die unless throttle is applied. Increasing the throttle slightly keeps the bike running, but barely. Revving the engine aggressively clears up the problem, and the bike then runs normally, and the problem does not return until the next restart.

The engine also runs rough on cold start, with the throttle advance engaged which it never did before.

It will also die occasionally when coasting to a stop after a long engine run, after pulling in the clutch.

Idle speed is ~1250
Valves and Synch are spot on
Throttle calbles seated
TPS voltage is at .390V at idle and stable
Triple checked all connectors
Checked FI spray patterns
New Plugs
New Stick Coils
New Fuel Filter

The only thing I'm missing is a way to check the fuel pressure at the rail. I have two different specs for the fuel pressure as well, 44 and 55lbs. not sure which is correct.

Will taking it to the dealer and paying for a Motronic Diagnosis help me here? I'm really hoping it's not the fuel pressure regulator, which means pulling the tranny for replacement.

Any ideas out there? Anyone have a spare male quick disconnect I can use to fabricate a fuel pressure tester?

[Dave_Faria]

I had the same problem. Mine turned out to be one of the stick coils. What I think caused one of the coils to fail is a poor ground. What I found on mine was increased ground resistance at running temperature. My fix was to clean the ground and apply antioxidant for aluminum. The ground lug and wire are on the back side of both cylinders. Fixed at 45k miles now at 60k miles with same bike 04R1150RT. I also cleaned the ground for the secondary coil under the gas tank just to be sure/complete.

Good Luck
Dave Faria
Austin, Tx

[jcridge]

I'm beyond frustrated with a nagging problem on my 55k mi. '04 R1150RT.

After a hot restart, subsequent to a 5+ minute heat soak, my RT starts and idles perfectly. About 10-20 seconds later, the idle speed drops 300-400 rpm, and the engine stumbles, coughs and sputters. Most of the time it will die unless throttle is applied. Increasing the throttle slightly keeps the bike running, but barely. Revving the engine aggressively clears up the problem, and the bike then runs normally, and the problem does not return until the next restart.

The engine also runs rough on cold start, with the throttle advance engaged which it never did before.

It will also die occasionally when coasting to a stop after a long engine run, after pulling in the clutch.

Idle speed is ~1250
Valves and Synch are spot on
Throttle calbles seated
TPS voltage is at .390V at idle and stable
Triple checked all connectors
Checked FI spray patterns
New Plugs
New Stick Coils
New Fuel Filter

?

I see you are a Lucas Man...95% of all fuel problems are electrical.

Here are a few things:

Bad fuel?

Dirt in bottom of tank, after sitting and then starting, it is sucked up on the pump sock, if it gets worse it will affect performnace as well.

Heavy carbon on back of valves.

Plug wires, poor voltage at idle causing misfire

O2 sensor, not sure on this one. Does BMW look at the O2 sensor at cold idle / warm idle? Most manufactures look at O2 when an operation temperature has been reached, and ignored at cold startup.

Keep us posted on what you find.