bwr Posted September 5, 2006 Share Posted September 5, 2006 About 3 ½ weeks ago (almost 4,000 miles now) I successfully did my first major tune-up: valves, plugs, TB synch, etc. Now it runs like a top when riding and just purrs at speed. Many thanks to all the folks who’ve posted on this board. I couldn’t have done it without everything I’ve learned from searching the archives. I set the idle as close to 1050 rpm as I could. At idle the needle on the tach sits its width above the 1 on the dial (with the bottom of the needle just touching the top of the 1’s line); when I apply the brakes at idle, and the servo kicks in adding its load, idle drops to 1K exactly. What I’ve noticed, however, is that it doesn’t idle perfectly smoothly. Every now and then it hiccups – just a bit, not much: this happens every 8 or 15 or 20 seconds (pretty random); for just a moment idle drops to about 900. It’s not as if the engine is in any danger of stalling or runs rough constantly – there’s just this little stutter every now and then. This tends to happen when the engine’s quite hot, idling in traffic on a hot day for example. I don’t notice it as much when it’s still warming up. Is this typical? If not, does anybody have any ideas what might be causing it? The idle was set pretty high before I adjusted it (maybe about 1300); but, honestly, I’m not certain if it was doing this before I played with it. Maybe I should increase the idle slightly – what do you think? Since it’s running so well in every other respect should I just leave well enough alone. But it would be nice if it would just purr purrrrrrfectly at idle like it does as speed. Any thoughts? (I'm beginning to think that wrenching on these things isn't a good activity for those of us inclined towards obsessive-compulsive behavior ) Cheers! Link to comment
rocks Posted September 5, 2006 Share Posted September 5, 2006 (I'm beginning to think that wrenching on these things isn't a good activity for those of us inclined towards obsessive-compulsive behavior ) errr... that would exclude most of this board No wonder there are so many discussions occurring where the participants are seeming quite testy Link to comment
adkbeemer Posted September 5, 2006 Share Posted September 5, 2006 Well, here is my .02....my 02 RT has the same little idle issue, always has. I narrowed it down to the O2 sensor function. It may or may not be your issue. The O2 sensor voltage at idle seems to run up towards rich (.46v to .8v) then drops to lean (.2v or so)- that is the drop you see in the idle. Then it swings up to rich, then the same pattern over again. There are all sorts of interesting affects from the 02 sensor that have already been discussed here, particularly as it relates to lean surging. For "fun" try pulling your CCP, do a Mo reset and see if it eliminates the idle drop.... Link to comment
smiller Posted September 5, 2006 Share Posted September 5, 2006 The O2 sensor voltage at idle seems to run up towards rich (.46v to .8v) then drops to lean (.2v or so)- that is the drop you see in the idle. Then it swings up to rich, then the same pattern over again.That cycling pattern is perfectly normal for an O2 sensor and it will (or should) do that at any speed, not just idle. The ECU looks at the duty cycle and magnitude of the swing to determine A/F ratio and one cycle will not cause an instantaneous change in the output of the ECU so there will not be a direct correlation to the voltage drop and an idle speed hiccup. Link to comment
adkbeemer Posted September 5, 2006 Share Posted September 5, 2006 Yeah, I know that its normal. I just wish I had a scope to observe the output voltage pattern better. I think it may be swinging too rich around the target voltage (best), which accounts for the Mo adjusting it way too lean on my bike.... Link to comment
adkbeemer Posted September 5, 2006 Share Posted September 5, 2006 OK, I don't disagree with you, in principal... My question is then why when the O2 sensor is disconnected or the CCP is pulled does the condition go away (o2 sensor disabled), the idle flattens out and in some cases goes up slightly? Lets say the idle mixture is overly rich (due to any number of factors). How long does it take for the O2 sensor/Mo to sense this and correct it? If it then "overcorrects" too lean, how long does it take for it to then allow the mixture to richen and the cycle to repeat? Would this be an indication of a "slow" or failing O2 sensor... Not trying to be contrary, just trying to learn... Link to comment
bwr Posted September 5, 2006 Author Share Posted September 5, 2006 The O2 sensor voltage at idle seems to run up towards rich (.46v to .8v) then drops to lean (.2v or so)- that is the drop you see in the idle. So, if I understand correctly (sorry, I'm a ludite!), there's not much I can do to remedy the irratic idle. This is just the O2 sensor unable to keep the mixture correct at idle (it can't respond quickly enough)? Maybe I should just ride and stop fretting Link to comment
smiller Posted September 5, 2006 Share Posted September 5, 2006 When you pull the CCP the idle mixture defaults to an internal preset value which will probably be somewhat different than that determined by the O2 sensor, so it wouldn't surprise me if idle speed changes a bit... but again the change is not due to the waveform of the O2 sensor output per se. There is a smoothing function in the ECU so instantaneous swings in O2 sensor output won't cause instantaneous events like a misfire hiccup. For this reason it's not very practical to try to determine O2 sensor health by noting engine operation... to test you need to look at the O2 sensor output voltage/pulse rate with a meter and verify that it's within parameters. Link to comment
adkbeemer Posted September 5, 2006 Share Posted September 5, 2006 I don't know if mine is the same issue as this. My idle actual drops and stays there for a second or so. I'm monitoring the voltage from the o2 sensor and it drops to .2 or so during the "drop" then climbs back up towards .8, then back and forth, then repeat. I realize that I probably have a bad sensor (I just discovered this during some testing last weekend, so my data may be off) or that my idle mixture may be way off. Just sounds a lot like the issue at hand..... Link to comment
T__ Posted September 5, 2006 Share Posted September 5, 2006 Brian, when at hot idle the idle mixture is pretty well held in check by the 02 sensor.. That little piece of engineering marvel really doesn't know idle from cruise throttle so tries to hold the idle mixture close to 14.7:1 (stokeometric) or at least as close as it can.. Problem is, that is just a little too lean for proper idle combustion on that large piston 1150 engine.. You can try disconnecting the 02 & I'll bet the idle improves a little.. Then maybe install a device like the Teclusion 259 as that allows a little fuel add at all throttle settings.. That usually improves the idle quality enough to notice.. Probably not silky smooth but at least even with a constant beat to it.. Opening the spark plug gaps to about .045"-.050” will also allow better ignition & better combustion on a lean running idle but I wouldn't recommend that with the stock ign coil & plug wires.. If you have the coil to pull that gap at high RPM's opening the plug electrode gap can really help a weak lean idle though.. Twisty Link to comment
Ken H. Posted September 5, 2006 Share Posted September 5, 2006 Well for starters, 1050 idle RPM is really a bit too low. The spec is 1100, and in general these bikes idle best around 1150 ish. That being said, a lumpy idle is not unusual nor, unless the bike actually trys (or does) to stall, anything to worry about. Link to comment
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