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Discussion Starter #1
Really need some assistance on this one....a few weeks ago after traveling a few miles on my 99 LTwould and coming to a stoplight the engine would idle rough between 1000 - 800 RPMs but would smooth out with an increase in throttle...last week after just a few minutes under throttle and coming to a stop the engine initially idle smooth at 1000 RPMs then dropped to 800 - 500 RPMs for a few seconds, followed shorty by a cutoff. This week it has gotten progressively worst and now after running for just a couple of minutes at idle, it will drop to 500 RPMs and then shutoff. Can start up imediately and after a few seconds RPMs drops down and shuts offs. Engine is very strong and smooth under acceleration and cruising and always starts immediately. Here is what I have tried so far with no luck:

-Canisterectomy performed correctly, tank is properly vented with no restrictions, no vaccum suction when removing the gas cap, plus all 4 vaccum leads vertified connected and secured to the intake manifold

-Checked Plugs, only have 3,000 miles and looked good, plug wires looked OK.

-Charged/checked battery, it's is 4 years old seems great and cranks the engine very strong (12.9v static, 12.5v key on, 10.4 cranking, 13.9v running)

-Tank drained twice and checked for blockage and any restriction in the filter...used gas from 2 different gas stations, plus ran fuel injector cleaner.

-Reset throttle position sensor 3 times.

My bike will not idle at all after running for a few minutes when first started, have tried everything that I can think of at this point......any other suggestions or solutions would be greatly appreicated.

Dave

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Hmmm....as you've verified that it's not a venting issue, it sounds to me like either a fuel pump on it's way out...or perhaps a dirty fuel filter. My guess is the pump. Both the pump and filter are inside the tank.
 

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Discussion Starter #4
I did take the pump/filter out of the tank and inspected them both....no restriction with the filter and when the key is first turn on the pump charges-up in about 1-2 seconds and sounds strong then turns off, engine starts immedately and runs very smooth and strong except at idle...maybe my battery is getting weak but always indicates 13.9v at idle.

Did not know about the fuel regulator, that could be it also....anyway to test it, not sure where it is located on the fuel rail.

Any other suggestions that I should try after the fuel regulator?

Thanks for all the assistance
 

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Miles of Smiles
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Isn't rough idle also a sign of a leaky vacuum line ?
Not having had this problem myself, maybe a search would help
 

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Discussion Starter #6
I did check all 4 vaccum lines and they were good, usually a leak makes the idle surge up and down above 1000 RPMs...unfortunately for me my idle drops very low usually 800-500 RPMs then shuts off after a while. Just don't know what else to check at this point. Thanks for your suggestion.
 

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I do a ton of engine stuff....Often overlooked, water in fuel? Take a nice high-flow sample from the fuel rail return perhaps? Won't hurt to rule out water....
 

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i would check the tps. i know you reset it but sounds like sympton of a bad tps. can usually be checked w' a dvom
john
 

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If in all of your checking you haven't disconnected the battery for more than a few seconds, you might try letting the computer reset itself by disconnecting the battery and letting it sit for an hour or so. Reconnect the battery turn the key to on and before starting be sure to fully open and close the throttle three times to let the computer relearn the positions. This should reset your system to the default maps. Now start the engine and see if that has any effect.

I always like to try the cheap stuff first before taking to a dealer.

Good luck,

Steve
 

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Discussion Starter #10
Excellent suggestions

- will sample the fuel and check for water, as I recall water will float to the top of a clear cantainer

- John, TPS failure is definitely a possiblity, not sure what volts/ohms readings to look for on the TPS check, could not find the test procedure searching the forum, would really like to check this one out if I can locate the test procedures.

- Steve, have not disconnected the battery for a long time....will do it tonight and reset my fuel map back to default

Thanks guys for the suggestions, hopefully I'm getting close to finding my problem.

Dave





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eaglepilot427 said:
Excellent suggestions

- will sample the fuel and check for water, as I recall water will float to the top of a clear cantainer

Dave
Drain a pint into a clear quart-sized mason jar, cap it, swirl it. The water droplets will form/tumble at the bottom of the vortex; water is heavier than petroleum. Hope this helps.
 

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eaglepilot427 said:
... as I recall water will float to the top of a clear cantainer -
Yep, what he said. The specific gravity of water is higher than gasoline....so the water, if there is any, would sink to the bottom.
 

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Engine idle speed is controlled by the Idle Air Controller (IAC) module. It sounds to me like you may have an issue there.
 

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Discussion Starter #14
Wacolt and Toolman,
Thanks for the water testing procedure, used it to test my fuel and it appears OK did not see any water droplets at all.

Dean
Do you know where the IAC is located and how to test it?

After draining the fuel to test for water and resetting the TPS/fuel map with the battery disconnected, the engine idle was perfect for over 10 minutes...thought the problem was fixed...took the Bike out for a short test drive and it started to idle low, but did not cut-off...I shut it off let it cool down and tried it again this time the idle was normal and very smooth. Looks like I have an intermittent problem that comes and goes...makes me think that it's not the fuel pump or filter. Any suggestions/thoughts

Thanks for all the help
Dave
 

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Hmmm...makes me think it might be the injectors starting to get dirty. Cold engine = higher idle via longer injector pulse (more fuel). As engine warms up, idle speed decreases (shorter injector pulse/less fuel) and the problem rears it's ugly head in this RPM range. Just a theory. Maybe try a can of injector cleaner juice...and see it makes any difference whatsoever.
 
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