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Discussion Starter · #1 ·
I know this has been an issue by reading previous posts. Changed the spark plugs, fuel filter, air filter. Removed the injectors, cleaned and verified that they are spraying correctly. Bike seems to run fine until it warms up. (3-5 minutes). Once it warms up it bogs on anything more than about 1/4 throttle. The bike did setup for a while, all fuel has been drained when the fuel pump was changed. The electric throttle blades are working correctly. Old spark plugs were black color. It very much seems to be directly related to temperature as it runs like a champ for the first few minutes. Could also be a flaky TPS sensor that flakes when warmed up. Fuel pressure is holding at 45 under load when bogging. It is not backfiring at all. If you decrease throttle to 1/4 the engine will pull, but bogs at any position over 1/4. This one is eating my lunch..

Bike has 7,000 miles on it.
 

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Welcome to the forum from North Carolina. Glad you decided to join us. You are making all the right moves in an attempt to cure this issue. Had this same throttle condition with my 900. Oddly happened right after filling up with high test gas. Went home, replace the plugs with the iridium type, replaced fuel with regular, put in can of Seafoam, and bike runs great. Other members will say the premium fuel runs great in these bikes, but not in mine. Wish I could be of more help. If you do not have a factory repair manual here is a link to download one.

 

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Laswampmn, does your bike have O2 sensors? Is it a California bike?

Ok, so here is my guess. Your bike did have O2 sensors. Since you confirmed everything related, including fuel pressure under load, here is what I think is happening. Someone removed the O2 sensors and put in those O2 sensor plugs. When the bike is started, it runs good open loop, since it takes a few minutes to warm up the O2 sensors, so they can be used. Then it switches over to closed loop, where it relies on O2 sensor feedback to control the mixture. It goes full rich (black sparks plugs) trying to get an oxygen cutoff signal from the O2 sensors, but it can't because the O2 sensors are not there. This is causing the bogging, because some dumb dumb removed the O2 sensors. They need to be put back in, so the ECU can control the mixture.

If this is wrong, then I'm the dumb dumb. 😃
 

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Discussion Starter · #4 ·
Jbiggers,

No O2 sensors on this one. Never had them, bike was running fine last year, but sat up for 3 months. Will be back probing the tps sensors this evening to see if they are flaky. Started it cold yesterday, and was bogging even when cold. Am thinking it is tps, second tps, or that throttle actuator not registering open.
Thanks for the suggestion.
 

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Discussion Starter · #6 ·
Both tps sensors test good, throttle actuator seems to be operating normally. Going to try and unplug the water temp sensor tomorrow and see if that makes a difference, since the symptoms seem directly related to temperature and engine warmup The speedometer works sporadically, has been like that for a few years, so I doubt that would cause an issue as it never has in the past.
 

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Let me ask you this. Have you owned the bike since it was new? Does it have an aftermarket exhaust system on it? Have you checked the air intake system, to make sure the air filter is not clogged up by a small animal? After a cold start, does the engine return to a normal idle after a normal warmup period? Whatever the issue is, it is effecting the air/fuel ratio. So, I'm asking these questions to try and narrow down the cause.
 

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Discussion Starter · #8 ·
Bought about 4 years ago. All stock. Was running great, no issues and then it sat for 3 months. Air filter and box all clean. Idles and does a normal warmup. I took it to the dealer yesterday for diagnosis. Will see what they say. This one is definitely eating my lunch. I disconnected the coolant temp sensor yesterday and ran. That made it idle poorly until warmed up, and the fan ran continuously. Made no improvement on the bogging issue.
 

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I know the MAP sensor and IAT sensor provide air data to the ECU. If I understand correctly, the MAP sensor (Manifold Absolute Pressure) provide primary data to the ECU on the amount of air entering the engine. The manifold's vacuum is directly connected to this sensor. The IAT sensor (Intake Air Temperature) provides secondary data to adjust air density based on air temperature. The real science in the ECU happens here, to determine how much air is entering the engine. The amount of fuel to inject to get the correct air/fuel ratio, is based on this air data.

The MAP sensor has an internal vacuum as a reference. I had an older car once with a first GEN EFI system that used a MAP sensor that failed. After replacing that sensor, everything starting working properly again. That sensor has to be accurate, or the mixture will be wrong. In more modern EFI systems, the MAP sensor has been replaced with a MAF sensor (Mass Air Flow) that measures the temperature of a hot wire across the intake, to determine how much air is entering the engine. Both systems work, but the MAF sensor is simpler and eliminates the IAT sensor.

A failure of the MAP sensor could cause this failure, though bad idle mixture is where this failure usually shows up. The problem could also be the IAT. I noticed there are tests in the maintenance manual for these sensors.

Good luck with your bike
 

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Discussion Starter · #10 ·
Thanks for all the help. I will post once I narrow down the issue. Dealer is going to let me know on Tuesday what they find. $67 might be worth it to pinpoint which sensor is flaking out.
 
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