Gas mileage drop after syncing TB's

drumminman

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It's gone from a consistent 38 mpg to 32 mpg.

At time of sync also changed plugs.

Things I've thought of:

1) used fuel line hose instead of vacuum hose to reconnect. It doesn't appear to be that different, but maybe it's too stiff to seal as well.

2) I didn't use whatever adhesive Suzuki used to connect vacuum hose to TB's when they assembled the bike. Instead I used zip ties on plastic T connectors of manifold, and fuel line clamps on TB's. Everything seems to seal well (see # 1).

One of the rubbler boots connecting the air box to TB #2 may not be sealing; the others are fine

Other than that I'm puzzled.

I've double checked everything to be sure I've reconnected correctly.

Other than mileage the bike runs great. A definite improvement in throttle response, the idle is as smooth as before.

I've put about 100 miles on the bike and the mileage seems to be the only thing out of wack.

Anybody got any ideas? Jinkster?

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This topic came up a while ago. Something to do with resetting the TPS (throttle position sensor). Try search, thats all I recall. sorry
 
Sometimes, the vacuum hoses are on there pretty tight, especially if it's been a long time since the last synch. What that means is that when you pull them off, they can tear. I suppose that could cause a vacuum leak.

What rpm did you synch at? Do an initial synch at 2500 rpm, then another at 3500 rpm and then recheck again at 2500 rpm.

I'm shootin' from the hip here.

--Wag--
 
(Wag @ Sep. 19 2007,16:46) Sometimes, the vacuum hoses are on there pretty tight, especially if it's been a long time since the last synch. What that means is that when you pull them off, they can tear. I suppose that could cause a vacuum leak.

What rpm did you synch at? Do an initial synch at 2500 rpm, then another at 3500 rpm and then recheck again at 2500 rpm.

I'm shootin' from the hip here.

--Wag--
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BINGO! Dude, Just back up of the twist a bit that's all.
 
does it seem to be running really rich?

i'm only guessing here, but i'm wondering if you have
a vacuum leak, and if you remembered to hook up the
IAP sensor under the air box.

as far as i know, there's no adhesive on the vacuum lines,
-- heat and time just get them stuck. i tent to try to break
them loose first by "turning" them with tools, then pulling
them off
 
Had EXACTLY the same problem after I did my TBs. Two things. Check/adjust TPS. Easy to do. Second and this is what fixed mine. Disconnect the battery and reset the ECU. The ECU was "remembering" where the zero position was on the TBs. You changed that position slightly, and the ECU thinks they are where they were and it richens the mixture.
 
(TallTom @ Sep. 20 2007,04:34) Had EXACTLY the same problem after I did my TBs.  Two things.  Check/adjust TPS.  Easy to do.  Second and this is what fixed mine.  Disconnect the battery and reset the ECU.  The ECU was "remembering" where the zero position was on the TBs.  You changed that position slightly, and the ECU thinks they are where they were and it richens the mixture.
Good suggestions!

1) I replaced all the vacuum line hose with fuel line hose (more robust) and clamped it to the TB's with spring clamps.

2)I did not sync at 2500 or 3500; only synced at 1200, though I did blip the throttle while I watched the gauges. Maybe I should try doing it at the different RPM's.

3) I did disconnect the battery for about 30 minutes when I was finished, mainly because the FI light came on and I wanted to reset the ecu. It worked because now no FI light.

4) I read somewhere on the board that the TPS is not supposed to be tampered with. Jinkster's post IIRC on "How to Sync TB's". How did you do this Tall Tom? I've done a search and couldn't find any "how to's".

5) I'm pretty sure there's no vacuum leak with the way I reconnected everything. I did remember to reconnect the IAP line beneath the airbox.

Looks like I'll redo it this weekend at the different rpm mentioned above.

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Thanks everyone!
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There is a little connector pigtailed into the harness under the seat area. It has 2 pins. My 03 is white in color and it was tucked into the wire bundle along the frame rail where the front seat rest. They use it to do diagnostics. With key off, take a paper clip and short the 2 pins together and then when you turn on the key you will see the diagnostics display with "I think if I remember right", it says COO and then there is a dashed line after that. The dashed line should be in the middle position. There is a thread somewhere on this and it has pics of where the TPS is and the way to adjust it. Also if you go to the Do It Yourself section, they have the manual pinned there that also shows the display and the adjustment. They obviously don't tell you to use a paperclip but the end result is the same process.

In my case my TPS was right on but when I recycled my ECU my MPG problem got cured.
 
(drumminman @ Sep. 20 2007,05:36)
(TallTom @ Sep. 20 2007,04:34) Had EXACTLY the same problem after I did my TBs.  Two things.  Check/adjust TPS.  Easy to do.  Second and this is what fixed mine.  Disconnect the battery and reset the ECU.  The ECU was "remembering" where the zero position was on the TBs.  You changed that position slightly, and the ECU thinks they are where they were and it richens the mixture.
Good suggestions!

1) I replaced all the vacuum line hose with fuel line hose (more robust) and clamped it to the TB's with spring clamps.

2)I did not sync at 2500 or 3500; only synced at 1200, though I did blip the throttle while I watched the gauges. Maybe I should try doing it at the different RPM's.

3) I did disconnect the battery for about 30 minutes when I was finished, mainly because the FI light came on and I wanted to reset the ecu. It worked because now no FI light.

4) I read somewhere on the board that the TPS is not supposed to be tampered with. Jinkster's post IIRC on "How to Sync TB's". How did you do this Tall Tom? I've done a search and couldn't find any "how to's".

5) I'm pretty sure there's no vacuum leak with the way I reconnected everything. I did remember to reconnect the IAP line beneath the airbox.

Looks like I'll redo it this weekend at the different rpm mentioned above.

rock.gif


Thanks everyone!
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There are certainly more experienced members chiming in here but here are my .02 as I just did the sync/plug swap and picked up 2-3 mpg.

1) Is the hose the same diameter/length as OEM?

2) I have read the sync should be performed at 1500 rpm. If you are running mercury gauges, especially without restrictors, and you get up around 4000 rpms you run the risk of feeding your engine mercury. And that is bad. Very bad.

3) No comment.

4) Setting TPS by the screw is tricky. Take your time and do a search and you should be fine. Much easier performed with a PCIIIusb. If you don't feel a stagger or hesitation down low you may not need to adjust.

5) You might have pinched the vacuum line or some of the adhesive is blocking the inlet. I would remove airbox and reattach everything. While your there, look inside the throttle body and clean any residue that has collected around the butterflys. Spray cleaner in a rag, not directly in the body.

In addition, I would suggest staying out of stop and go traffic and ride the highway at a consistent 60 mph to effectively gauge MPG. Also, make sure the air filter is clean and run a bottle of fuel injector cleaner to clean up the injectors.

GL
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(TallTom @ Sep. 20 2007,04:34) Had EXACTLY the same problem after I did my TBs.  Two things.  Check/adjust TPS.  Easy to do.  Second and this is what fixed mine.  Disconnect the battery and reset the ECU.  The ECU was "remembering" where the zero position was on the TBs.  You changed that position slightly, and the ECU thinks they are where they were and it richens the mixture.
Interesting.

I'll have to look resetting my ECU and also reinstalling my map just in case.

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Problem Solved!

Yesterday I decided to check the TPS by following Tall Toms how to. Pulled up the code and it's correct, with the display reading COO and
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the dash in the middle position.

Next I decided to disconnect the battery once more to reset the ECU. I had already done this once, but I was out of options at this point.

Decided to take her out for a little ride, and voila! Between 39.4 and 40.7 mpg on the digital gauge (with some wot), which I've previously found to be accurate. This is up from 32.2!

Oh yeah, before the ride I checked the air pressure in both tires - 30 psi! Got 'em back up to 42, so that may have helped a little too.

So, with help from the org problem solved.
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Thanks for everyone's help!
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Thanks for letting us know. Great group here, eh?

--Wag--
 
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