2003 VRF misfire, running rough

Have a problem with my 2003 VFR. Bought it 2 months ago, 2500 miles, mint. After it gets hot, 30 miles of riding it starts missing, running rough, worst under 5000 rpm (you can feel and hear it in the exhaust). Replaced the spark plugs, noticed the right front and right rear cylinder spark plugs very dark. After replacing the plugs ran great for 100 miles and started running bad again today after a 150 mile ride. Pulled the front 2 plugs and the left front looks clean, right front dark.

Bike is all stock except the flapper mod.

Was thinking I have a coil breaking down after hot.

any ideas?

Jeff

 

Inspecting and replacing the plugs was the best way to begin.

Obviously, any one plug that isn't firing or fouling out will cause rough running, and you should keep trying to isolate the problem to one plug consitantly, which could be electrical or FI related.

You should be able to test the plug wire when hot for spark.

 

FYI doesnt have spark plug wires. Has coil on plug.

 

Agreed with Squirrelman. You need to check for spark when the coils are hot. If that test is inconclusive then you can swap coil packs around and see if the fouling spark plug follows the coil pack or stays with the same cylinder.

 

Update...

Pulled the plugs (again). The right front and right rear again are gas fouled. Cleaned them and reinstalled. Moved the coils to different cylinders to see if the issue follows the coils. Runs fine now but well see after a ride.

Question... What is the cylinder arrangement? LF #1? etc..

Jeff

 

Question... What is the cylinder arrangement? LF #1? etc..

Jeff[/QUOTE]

Right front is no. 4 Left front is no. 2 Left rear is no. 1 and right rear is no. 3. It should be stamped on the head by the coil packs and the coil wires should have a corresponding number tag. FYI I've never had luck with cleaning a fouled spark plug on a bike, always had to replace them.

 

FYI I've never had luck with cleaning a fouled spark plug on a bike, always had to replace them.[/QUOTE]


I find this method is quite effective! LOL

 

If you're having trouble consistantly with 2 plugs, that could point to a problem with one of the two pulse generator coils, and those can be resistance-tested.

 

Have you tried swapping the coil packs to different locations to see if the problem follows the packs?

Disregard! I see that you have...........

 

Another update... Now I have 3500 miles, 3 spark plug changes, swapped coils and still have an engine miss, #3 and #4 spark plugs look very dark and fuel fouled. The plugs last about 200 miles before the dreaded missfire sets in. After some research ive learned 1 O2 sensor reads #1 & #2 cylinders and the other reads #3 and #4. Im wondering if I have an O2 sensor for the #3 and 4 cylinders reading lean so its pouring the fuel to it.

Any ideas?

Ive ridden it mellow and ridden it hard and no difference. The missfire can be felt below 5000 and smooths out above that. At idle it can be felt and heard inthe exhaust. New plugs runs smooth as silk.

Im about > < close to just selling it and buying a FZ1 ive had my eye on.

Jeff

 

Dude, yo bitch must be throwing FI codes like an angry wife throws dishes, so get in there and replace whatever component failed, then ride in peace and harmony.

 

You may be on to something there with the separate O2 sensors. If you had an oscilloscope you could monitor the sensor to detect if a lean bias exist in the voltage. Or you could swap the sensors side to side and see if the problem follows.

But the best solution--you should just go ahead and replace the O2 sensor on the afflicted side. Why? Because you have been running rich and fouling spark plugs, and all that rich exhaust has been flowing downstream and fouled the O2 sensor also. So now the fouled O2 is not reading correctly (indicating lean) and the dam computer compensates by sending an even richer mixture. Pull and inspect the O2 to see if it is covered in soot and let us know...It might be possible to burn them clean with the propane blower trick.

Wow LA just kicked the devils 4-0 in the third game!

 

Thanks to all the replys but.... I found the problem (thanks to another forum). The fuel pressure regulator is leaking through the diaphram and sucking though the vacuum hose.

Im ordering some more plugs, FPR and well see how it does.

Jeff