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Help! Rough idle after TB sync and TPS reset

D

dirtymartini

Just got it firing!
Joined
Aug 30, 2012
Messages
19
Location
PA
I am ready to pull my hair out....I did a TB sync and TPS reset,now I can't get a smooth idle. I have gone back through it several times and thought I had it only to have it start idling rough again.

I am thinking I have the air bleed screws effed up.....How much should they be open? I read in the TB sync tutorial the right should be almost closed and the left open slightly?

The only other thing I did during this was change out my spark plug caps with the NGK caps.
 
I used a Twinmax and the tutorial here on guzzitech. With the sensitivity almost maxed on the Twinmax the sync looks good both at idle and 4,00rpm.
 
What do you mean by rough idle...won't stay steady??

Does it idle fine at first (you said the idle balance was good) and then after a time it goes to rough idle.

What was the TPS reading at the end of the syncing after you reset it once the idle was balanced.?

Did you put the vacuum tubes back on tightly?

Usually, the right TB screw is fully closed. The left is about 3/4 to 1 turn out (at least on mine). You only adjust one screw.

Assuming you moved the correct balance screw for adjustment and not the sacred screw for the balance???



On the NGK plug caps, I find you need to push them down tightly. Thought I had mine on then they clicked one more time. Although I would think that if you can sync the throttle bodies that there is nothing wrong with the wires.

Sorry for all the questions, just need more info.
 
I thought I had it a couple of times,then when I disconnected the Centurion and Twinmax and went for a test ride it would act up again...idle ok for a few seconds then act like one cylinder would miss,then idle again.

TPS was at 4.8 after reset.

Vacuum hoses back on tightly
 
Only one air bypass screw should be open. If both are open, you can get the symptoms you describe.
 
dirtymartini said:
I thought I had it a couple of times,then when I disconnected the Centurion and Twinmax and went for a test ride it would act up again...idle ok for a few seconds then act like one cylinder would miss,then idle again.

TPS was at 4.8 after reset.

Vacuum hoses back on tightly
Click to expand...

My vote is on a bad plug wire connection from when you changed the caps. Did you perhaps pull the other end of the wire from the coil (behind the side panels on both sides). My connection to the Stelvio at the coil was very loose and had to tywrap it in place so it did not come out. It had actually wiggled out on its own at one point. Quite possible you pulled it loose when changing the caps trying to get more slack.

Strange that it would idle fine, then not. If it was a balance you would expect it to be out all the time. If your meter is showing balanced at idle when it is connected, only other thing is the vacuum lines have a hole when you reconnect them but that would be pretty coincidental and I am not a big fan of coincidents.

Check out the wire connections at both ends on both cylinders. Make sure they are tight and snapped in all the way. Make sure your new caps are tight to the wire then try it again. It will be something simple.
 
john zibell said:
Only one air bypass screw should be open. If both are open, you can get the symptoms you describe.
Click to expand...

Here's the last "tweak". Right side air bleed screw lightly seated,left side open maybe 1/2 turn. Still had a bit of rough idle. TwinMax close to zero at max sensitivity.

I know Todd is not going to believe this one but I started playing with the Centurion fuel trimmer (idle) and at +10 (richer) I could hear the idle settle down. Maybe this was compensating for a bad air bleed adjustment?
 
Here's a of rule of thumb that I don't always follow, but keep in mind.

If something has changed, gotten worse, recently, check that last thing you worked on.

Depending on my certainty of the diagnosis or depth of understanding in the systems I'm working on, I'll limit the changes I make to one in order to isolate any symptoms to the changes made.

Recheck the SP cap conductor connection. I'm betting on spark too.

DM, did you close the 2nd air bypass? If not, close it. Adjust balance with the negative side only. Can you tell if the rough idle is going low then surging to come back to spec or is it surging high and being depressed back to spec?

Idle also improves by plugging the evap vacuum line at the manifolds. Essentially this is a small vacuum leak. Plugging it helps richen the mixture and improves idle noticeably in warm/hot weather. I suspect that a balance tube is a hold over from the carb days, with EFI the tube still sucks air because of the injection timing.

Also, make sure your condensate discharge tubes are not disconnected from the air filter box. These things run so damn lean that any little thing throws things off.
 
I definitely broke one of my rules by making more than one change at a time. I am starting to think spark also, It will idle nice for a bit and then start skipping a beat here and there. I have been through the TB sync several times now, I feel I have it set right.

I only replaced the SP caps, maybe I should try replacing the wire also?
 
Did you check the other end of the wire that plugs into the coil to make sure you didn't pull it out???



canuck1969 said:
dirtymartini said:
I thought I had it a couple of times,then when I disconnected the Centurion and Twinmax and went for a test ride it would act up again...idle ok for a few seconds then act like one cylinder would miss,then idle again.

TPS was at 4.8 after reset.

Vacuum hoses back on tightly
Click to expand...

My vote is on a bad plug wire connection from when you changed the caps. Did you perhaps pull the other end of the wire from the coil (behind the side panels on both sides). My connection to the Stelvio at the coil was very loose and had to tywrap it in place so it did not come out. It had actually wiggled out on its own at one point. Quite possible you pulled it loose when changing the caps trying to get more slack.

Strange that it would idle fine, then not. If it was a balance you would expect it to be out all the time. If your meter is showing balanced at idle when it is connected, only other thing is the vacuum lines have a hole when you reconnect them but that would be pretty coincidental and I am not a big fan of coincidents.

Check out the wire connections at both ends on both cylinders. Make sure they are tight and snapped in all the way. Make sure your new caps are tight to the wire then try it again. It will be something simple.
Click to expand...
 
Yes, I checked the coil ends....they were secure.
I put on a little over three hundred miles today and experienced rough idle a couple of times. Of course when I came home and pulled in the garage it idled nicely. It seems to me if I was out of sync or had the air bleed screws messed up it would idle rough all the time.
 
After my 350+ ride on Sunday I checked my fuel mileage. On board computer said my average was 43.5 but when I did the math miles/gal it came out to 31???????

I'm still not satisfied I have everything right on my idle mixture but that shouldn't affect my fuel mileage should it?
 
I had an injector go bad, rare I know but it did effect the idle and my mpg which was down to around the 30mpg mark...

windy
 
DM. Did you see that I also changed my plug caps and had a day of bad running? I pulled them to find I could still crank the right side down by a good two turns. also gave a push on the left side to feel it actually click altho I thought I felt that the first time. Needless to sa, mine started running great after that.
 
Toadride said:
DM. Did you see that I also changed my plug caps and had a day of bad running? I pulled them to find I could still crank the right side down by a good two turns. also gave a push on the left side to feel it actually click altho I thought I felt that the first time. Needless to sa, mine started running great after that.
Click to expand...

I did see that. I double checked and they are snapped all the way down. I have a fairly decent idle now and it is smoother running through all rpm's after the TB sync.

What really concerns me now is my fuel mileage. The info display says 43 but the math comes out to 31.....somethings not right!
 
If you have access to VDSTS or similar, see if the lambda voltage indication is changing once teh bike warms up. A faulty lambda will result in poor mileage, but it usually would be evident from the dash readout as well as calculated.
 
john zibell said:
If you have access to VDSTS or similar, see if the lambda voltage indication is changing once teh bike warms up. A faulty lambda will result in poor mileage, but it usually would be evident from the dash readout as well as calculated.
Click to expand...

Oh yes, I forgot, I had to have a new one of these as well... :whistle:
 
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