CB900F (919) running rich - ECT?
Hey Guys, Need help with my '05 919
A few months ago the Honda snapped a throttle cable. I tried to hook a new one up with the throttle bodies still on but just could not get it in the hole/slot so I stripped it down to remove the throttle bodies (TB) as per the service manual. I was not confident of getting the TB off without damage because they were stuck on pretty good so I trailered the bike to a local shop to pull the TB off and fit the cable for me. Job done I trailered the bike home and put it back together.
While apart I took the opportunity to check valve clearance, change plugs and replace all fluids. It was due for a service.
When I get it back together I had the common issue of a slight misfire between idle and about 3500 rpm. I had to ride the clutch a bit more to take off. Above 3500 rpm it was running fine. If it was a carbied bike I would suspect that the choke was still engaged on a warm engine.
I took the bike back to the shop and got informed that it was the MAP sensor. I brought a second hand one, at least thinking it would make a difference. No difference. The shop then started blaming the TPS. I found the brilliant thread where you got the Honda Civic one and modded it (thanks guys it saved me a fortune). This made no difference. By this time I was starting to loose faith (and money) and decided to do the diagnostics myself and save the money.
Judging by the plugs it appears to be running rich. when I pulled the plugs out after about 100km plugs 1,2and 4 were covered in carbon but they were not consistently across all 4. I cleaned them up and reversed the order of the plugs (plug 1 into cyl 4 and so on) to see if it was the plugs or fuel. It appeared one plug was pretty much stuffed as it was the worst of the lot in cyl 1 and cyl 4 but any plug in 1 and 2 cylinders were fouled up as well.
I have had a good search of this forum which has been a great source of info and have checked many things.
There are no alarms on the MIL. I cleaned up the ground on the frame.
I checked the FPM for leaks. None apparent. I checked the voltages and resistance on MAP, TPS, IAT and ECT. They all were withing tolerance with the exception of the resistance of the ECT. The manual 2.3-2.6K Ohms @20 deg C. The ambient temp was about 27 deg C and I got a resistance of 1.83K Ohms. This seemed a bit low to me even with the temp difference. This was backed up by the fact that the bike seems to run a lot cooler now according to the gauge. I had it running for at least 5 min with some generous blips of the throttle and the gauge barely made it over the cold engine line. The fan did not start at all.
I seem to remember reading somewhere( but cant find it again) that the ECU uses the ECT temp to change the ECU map to richen a cold engine to effectively be an electronic choke. Please correct me if this is wrong. If this is the case could the ECT sensor be the issue with my running rich problem? Not sensing warm engine and not changing the ECU map
Sorry for the long winded explanation. There are some pretty knowledgeable guys on the forum so I am hoping someone Can help with this. I need the Honda up and running for work and riding it in peak hour like this is a bit risky.