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Discussion Starter · #1 ·
I was riding out on the back roads a few weeks ago, and as I was driving past an Indian casino, I noticed they had a gas station and having learned its best to have a full tank when ever possible, I stopped and filled up. about 20 miles later my motor started sputtering during acceleration as well as when at idle although to a lesser extent. I got home with a 3rd of a tank and figuring I got some crap gas, I stopped and put some 76 and seafoam in it. Its been some lousy weather here and I haven't gone out until today. Initially, it ran great but after stoping at my dealer for a burger and a part, But I started getting the jerking and studding again. The tach at idle goes from 1100 to 1800 back and forth instead of a steady RPM . Could this be something else? electrical? I have only driven about 50 miles since the casino gas so I wonder if that could be the trouble still?
anyone have any ideas?
 

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You can try to refresh the gas but I suspect it's fuel pressure related. A quick test is in order. 57-60 psi and should hold after pump stops if perfect. It should also hold this in higher engine rpms. If it slowly drops to like 40 psi in about a minute, that's fine but a sudden drop shows a bad leak in the lines, or check valve. Some will hold pressure indefinitely but not all do. Two main things you want to see is it holding normal pressure at higher rpms and no sudden drop in pressure when the pump stops.
Hard starting, idle hunting and missing or stutter is common to low fuel pressure.
Ron
 

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Discussion Starter · #4 ·
Thanks for the advice. As I don't have the equipment to check pressure in the lines, I'll have to ask you if there is a way to diagnose this manually. I will run or syphon the fuel out completely first as suggested and hope that works, if not I will look for a leak which I assume will be in the fuel lines, connections or gas cap. This bike was a one owner garage queen I bought last year and now it has 12k on the clock, so it's all in great condition.
 

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Thanks for the advice. As I don't have the equipment to check pressure in the lines, I'll have to ask you if there is a way to diagnose this manually. I will run or syphon the fuel out completely first as suggested and hope that works, if not I will look for a leak which I assume will be in the fuel lines, connections or gas cap. This bike was a one owner garage queen I bought last year and now it has 12k on the clock, so it's all in great condition.
I'd but the gauge set up from an auto supply. It's the older GM based that uses the R12 fitting.
As far as a quick test to rule out massive leak, turn the key on and run switch to allow the pump to cycle and quit. Pull the fuel pump fuse, wait 10-15 seconds and try and start the bike. It should fire and then quit right away. If it doesn't fire at all the pressure has bled off too much. The gauge is the best method however.
Ron
 

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Discussion Starter · #6 ·
I just went outside and fired it up.
It's been sitting there a week in the cold. Took a second longer to fire up but idles at 1100 steady. I'm gonna take it out for awhile and try to burn this fuel off.
 

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Discussion Starter · #7 ·
Today, I paid much closer attention and noted that at 2500 rpm minor studdering starts and gets worse between 3-4000 rpm. At 4000, it really smoothes out. I'm reading on the forum this is a common tuning issue but my motor, air intake, filter and exhaust are all stock and this issue just started last week. Would lean tuning suddenly just now start this issue? Can I install a tuner with the stock set up and how difficult are they to use? The local dealer won't even change pipes yet alone touch anything
related to emmissions etc (California) so I stuck where to start next.
 

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Mike,
You should be able to borrow a fuel line pressure gauge from Autozone. Napa, Advance or other Auto parts stores free of charge.
It hooks up to a Schrader valve located on the right side of the throttle body between the two jugs. Simple 5 minute check.
 

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Today, I paid much closer attention and noted that at 2500 rpm minor studdering starts and gets worse between 3-4000 rpm. At 4000, it really smoothes out. I'm reading on the forum this is a common tuning issue but my motor, air intake, filter and exhaust are all stock and this issue just started last week. Would lean tuning suddenly just now start this issue? Can I install a tuner with the stock set up and how difficult are they to use? The local dealer won't even change pipes yet alone touch anything
related to emmissions etc (California) so I stuck where to start next.
If it ran fine before the condition is caused from a mechanical/electrical reason effecting the tune, not the tune itself. Any fuel pressure issues, lowering the psi will make the bike run leaner on the existing tune. The EPA tune is leanest in those areas to start with so the slightest reason it got leaner as in lower psi, it shows up here first. Like RustyG stated, go rent a tool and find out if that's the issue. They are not expensive either and a good addition to the tool box. Cheaper then having a dealer check it most times.
Ron
 

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Discussion Starter · #11 ·
You guys are a great help to me, This is my first FI bike and all of this is a learning experience. A little more complicated then changing the jets...As soon as all this holiday cheer subsides, I'll get my hands on a fuel pressure gauge and if that's in the range it needs to be, I'll go to the IAC which I never heard of until today but from reading on the forum,, could probably use some attention. Thanks again!
 

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Discussion Starter · #12 ·
Today, I got a little time to try to solve the power loss, studdering and bad idle problem. I got a couple of good suggestions, one was to clean the TB and IAC port and check the fuel pressure. I thought I would try the TB and IAC cleaning first and then buy a pressure gauge . I warmed up the bike, and then opened up the throttle body and soaked them and the port pretty good. The valves had all kinds of black gunk on them, Let it cook there for 15 minutes, put it back together and fired it up. Right away the motor sounded like it was ready to go race. Took it out for a short run to blow the crap out and the hesitation, studdering is gone with a noticable increase in power. Smoked like Bogart though and ran smooth at 3500 rpm. I will have to take it out for a couple hours long ride to make sure it's good now, and if not, I will check the fuel pressure for leaks. I learned a lot from this problem and folks in here. Just hope this was THE fix.
 

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Today, I got a little time to try to solve the power loss, studdering and bad idle problem. I got a couple of good suggestions, one was to clean the TB and IAC port and check the fuel pressure. I thought I would try the TB and IAC cleaning first and then buy a pressure gauge . I warmed up the bike, and then opened up the throttle body and soaked them and the port pretty good. The valves had all kinds of black gunk on them, Let it cook there for 15 minutes, put it back together and fired it up. Right away the motor sounded like it was ready to go race. Took it out for a short run to blow the crap out and the hesitation, studdering is gone with a noticable increase in power. Smoked like Bogart though and ran smooth at 3500 rpm. I will have to take it out for a couple hours long ride to make sure it's good now, and if not, I will check the fuel pressure for leaks. I learned a lot from this problem and folks in here. Just hope this was THE fix.
Generally the IAC is out of the picture at around 2k at most. Found this out when syncing the throttle bodies on my 13 DX. It will effect the idle part of your condition. Spark plugs might have been crudded up so the treatment might have cleared up the higher rpms. Good to know it's working better now.
Ron
 

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Ebay sells a fuel pressure gauge for a GM Corvette. It attachs through an adapter on the Schrader valve on the fuel rail. Gauge ends up behind the vertical coolant hose and right under the frame rail. Easily accessible but you can't see it when riding. Looks good to boot. I leave it on there all the time.
My only con is it was tough getting he adapter tight enough to not leak. Needed a crowsfoot wrench to torque it tight enough. Was a little scary going into an aluminum fuel.
 

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Discussion Starter · #15 ·
Ok so here I am again...I started trying to find the problem first by cleaning the TB .flushed it all out, then took it out around the block and it ran great. I thought the problem was fixed until I took it out again. Went further this time and the studdering under 4k
Started Again. Per Ron's and Rusty's suggestion bought a guage and ran a fuel pressure check, once I got the air bubbles out and up to warm idle it ran at 50-52 psi. Revved up up to 5k, still remained pretty steady at 50 psi. I think this is low and it should read between 55-65 psi. Do you guys think I could have a leak somewhere??Clogged fuel filter? Loose TB Or Something else? Is 50 psi acceptable and if so should I look for an ignition/spark issue ? I think some other folks had to deal with the same issue, but it actually seems to be getting worse. Thanks ?
 

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Ok so here I am again...I started trying to find the problem first by cleaning the TB .flushed it all out, then took it out around the block and it ran great. I thought the problem was fixed until I took it out again. Went further this time and the studdering under 4k
Started Again. Per Ron's and Rusty's suggestion bought a guage and ran a fuel pressure check, once I got the air bubbles out and up to warm idle it ran at 50-52 psi. Revved up up to 5k, still remained pretty steady at 50 psi. I think this is low and it should read between 55-65 psi. Do you guys think I could have a leak somewhere??Clogged fuel filter? Loose TB Or Something else? Is 50 psi acceptable and if so should I look for an ignition/spark issue ? I think some other folks had to deal with the same issue, but it actually seems to be getting worse. Thanks ?
50 is not acceptable. Calibration would be based off of 57 minimum and anything below that will lean the mixture out. A leak is possible, a weak pump or even the regulator could be at fault. Now having said that, gauges can be notoriously inaccurate. If you can find another gauge to spin on, I'd do that to compare. This can be any gauge, air, oil or whatever as long as it's in the reading range.
Ron
 

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Discussion Starter · #17 ·
Thanks, Don t think I can get access to a second one though. By the 50 psi pressure, I'm guessing a slight leak somewhere, I started going up the pressure and return lines and noticed the the blue button connectors seem to slide 2 mm back and forth without the buttons being pushed in. Are there servicable o rings in there ? How's does one tell if they are leaking? No fuel leaking from them. There's a service bulletin
On the fuel flange but mine isn't on the list. The only thing I can think of from there is pulling out the fuel module and as you mentioned inspecting the components. Would leaking from the internal gas lines produce any bubbles inside the tank?
 

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If you have a leak:
Attach gauge.
Turn ignition on and check pressure.
Turn ignition off.
If pressure drops quickly you have a leak. If no leak then it will drop ever so slowly or not at all.
Auto parts stores have free loaner gauges so no reason to not borrow one or more unless there are no auto parts stores close by.
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You may just have a clogged fuel filter(s). There are two of them in the tank.
 
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