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Missing/popping/sneezing at idle


Tinus89
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Yeah I remember Docc tearing hair out over it until he tested the TPS.

 

I tore my hair out until I discovered the fuel return hose nudging the TPS ever-so-slowly out of spec. Over and over.

 

That being said, my bike, although running sweetly as ever, does occasionally hiccup....just once.....usually at idle.

 

I always freeze......oh shit...!.....then relax when it disappears and so I take off.

That TPS "budge" from the regulator connection was a great find!  :thumbsup:   I added it to the Tank Off Maintenance Checklist and watch mine carefully.

 

I could not see my TPS fault watching millivolt changes while opening and closing the TPS. I had to disconnect it and read Ohms (I can't remember what scale: milliOhms?) When I saw it *jump* at the same opening point every time, I knew the TPS was shot.

 

I have found fuel selection makes an enormous difference in hiccuping. I can no longer find non-ethanol fuel above 90 US Anti-Knock Index, but am having great results with US Shell 93 AKI  "V-Power Nitro+". When I run other fuels, even at that AKI, I get more hiccups.

 

(I am given to understand that US 93 =~ 98 Euro fuel?)

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Season 2016 i have a same kind serious running problems , less than 2000km that summer.  Two bikeshop try to fix it -no result. Next winter i change all relays to Omron (have to order them US) and now it`s running ok.

I use carbtune and i don't try to get exact same balance but instead best possible and when meter columns react same kind -rise and fall. Bypass left 1/4 & right 1/2 turn open.

 

-KG-

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Yeah I remember Docc tearing hair out over it until he tested the TPS.

 

I tore my hair out until I discovered the fuel return hose nudging the TPS ever-so-slowly out of spec. Over and over.

 

That being said, my bike, although running sweetly as ever, does occasionally hiccup....just once.....usually at idle.

 

I always freeze......oh shit...!.....then relax when it disappears and so I take off.

 

That TPS "budge" from the regulator connection was a great find!  :thumbsup:   I added it to the Tank Off Maintenance Checklist and watch mine carefully.

 

I could not see my TPS fault watching millivolt changes while opening and closing the TPS. I had to disconnect it and read Ohms (I can't remember what scale: milliOhms?) When I saw it *jump* at the same opening point every time, I knew the TPS was shot.

 

I have found fuel selection makes an enormous difference in hiccuping. I can no longer find non-ethanol fuel above 90 US Anti-Knock Index, but am having great results with US Shell 93 AKI  "V-Power Nitro+". When I run other fuels, even at that AKI, I get more hiccups.

 

(I am given to understand that US 93 =~ 98 Euro fuel?)

Yes docc US 93 is 98ron

 

Ciao

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Ok, here is what I did:

- Reset both air bleed screws at 3/4 turn open

- Adjust balance using white knob

- Set idle a little higher, around 1350rpm on the gauge (forgot to bring my laptop, so could not check GD)

 

Observations:

- I am an idiot as I did not back off the RH idle raiser/choke screw last time, hence all adjustments I did last time were not perfect

- Drivability has significantly increased! Still some pops when opening the throttle at idle, but significantly better!

- I measured TPS resistance between the two wires. When i start opening the throttle real slow, it starts off at 1070Ohm, slowly dips to 1065Ohm, slowly rises to 1200, dips to 1170, rises further.

There are some minor dips every time (does not matter whether I use the throttle lever or the connecting rod), but is this an issue, or normal?

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Progress! Good news! :thumbsup:

 

My understanding is the the resistance through the TPS potentiometer should progress smoothly and evenly with no jumps or dips. I replaced mine with the much (much) cheaper Harley-Davidson part (Magneti/Marelli PF 4C) that has a different output curve (per our respected Meinolf), yet it has worked well for my purposes. (I also use hammers a lot . . . :whistle:

 

So, with the Right Hand idle stop screw defeated, you have reset your TPS 157mV baseline with the throttle plate fully closed? This step is critical as it indexes the throttle position to the ECU mapping.

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So, with the Right Hand idle stop screw defeated, you have reset your TPS 157mV baseline with the throttle plate fully closed? This step is critical as it indexes the throttle position to the ECU mapping.

 

Yes, that is the exact way I set it:)

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- I measured TPS resistance between the two wires. When i start opening the throttle real slow, it starts off at 1070Ohm, slowly dips to 1065Ohm, slowly rises to 1200, dips to 1170, rises further.

There are some minor dips every time (does not matter whether I use the throttle lever or the connecting rod), but is this an issue, or normal?

Like Docc says, that resistance change you measured is a problem.

See the test graph picture on the Web page

http://ca-cycleworks.com/pf3c

 

Things will be better with a new TPS.

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  • 4 years later...

Rather than start another thread on this, I’ll bump this one and add to it: (I’ve alluded to this mildly annoying issue in other threads..)

Red LeMans has always run pretty sweet.  As I’ve noted elsewhere, this season for the first time I’ve got an issue with idle and low rpm that’s characterized by:

1) might be hard to get it to keep running at idle, after it initially fires off during start.  Idles, then stumbles and quits.  

2) idle speed seems to vary more than it ever used to, on its own.  Due to that rough cold idle, I’ve messed with air screws and TB sync a bit more (after full descent tune up) to try some different fine tuning, with no real change.  But when I’ll turn up the idle a bit to around 1250, when its warmed up, then next ride it will idle back at 1000, then a week later will idle at 1300.  Some variation was normal, but she never did this much. 

3) seems to run great on the road, but in neutral in the shop at 4,000rpm, checking the TB sync, it will stumble a bit, and i can feel the throttle tension release momentarily when that happens (I’m thinking thats a solid clue).  And before this riding season, she used to actually remarkably well even between 2500-4000 rpm, where some MG’s of this vintage commonly have some burbles.  But now I’ve got a solid burble most of the time in that rpm range.

throttle linkage “tunnel” is all clear, TPS was all dialed in, requiring very little adjustment on the last tune up (early summer, about 100miles ago), valves were good needing no adjustment. 

Only new thing I’ve done this year is I usually will adjust the right throttle body idle screw in till its just touching the lever, once all the tuning and idle adjustments (left side) are done.  I left it all the way out this time.  Shouldn’t make any difference, but its a change. 

I’ll just be messing with this issue during this late-starting riding season, but curious if others have thoughts. 

Cheers

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Have you checked the TPS for a smooth progression of changing resistance as it is slowly opened and closed ( no "jumps" or "dips") as Tinus89 did above? A faulty TPS can be maddening . . .

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9 hours ago, docc said:

Have you checked the TPS for a smooth progression of changing resistance as it is slowly opened and closed ( no "jumps" or "dips") as Tinus89 did above? A faulty TPS can be maddening . . .

That’s probably the best next step.  Not bad enough yet to make me want to put her “out of service” in the middle of our short-ish riding season here, but that will be on the hot list for when the rains come. 

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