Wildguzzi.com
General Category => General Discussion => Topic started by: ohiorider on September 14, 2015, 07:18:32 PM
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AT 60,000 miles, I realize the high idle may be/or is caused by oil vapor build-up disrupting the stepper motor. But after doing a very careful TPS and TB balancing routine, I am now experiencing something that makes me think it is a line or two of code causing it. The bike is my 2008 2v 1200 Sport with a Marelli 5AM ECU. Here's the symptoms:
- After the TPS reset and TB balance, she has never run smoother. And the TPS and TB were off quite a bit. That was my doing.
- However, though the engine doesn't rise to 1600-1800rpm, she does want to idle at 1200-1300rpm when:
- In gear with clutch handle pulled in at a stop.
But when I put the tranny in neutral:
- idle drops to 1100rpm
And when I stay in neutral and pull in the clutch:
- the idle stays at 1100rpm
However, when I drop the bike into 1st gear, the idle begins to hunt between 1100 and 1300+ rpm. If I return to neutral, idle drops to 1100, whether the clutch is pulled in or left out.
Seems like the ECU sees the tranny is in neutral and jumps to one line of code, and when the neutral light is out, the ECU selects another line of code, advancing the idle speed.
Too strange! But what the hell .......... this old gal has never run better since I've owned her, aside from the weird idle issue.
I like the 'old' two valve 1200 so much I may have to find another, once the 8vSE moves out and leaves some space. eBay seems to be taking care of that matter currently. Hate buying high and selling low, but I guess that's the way of the (Guzzi) world when one buys new. However, if I average out the initial and ongoing cost of the 1200 Sport and Griso , and include fun per mile, it's ok!
Bob
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What's the question?
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What's the question?
Question is ..... why does the engine idle at 1100rpm as long as the tranny is in neutral, whether the clutch is engaged or disengaged? Any why does the idle immediately jump to 1200-1300rpm once I put the tranny into first gear? Cannot believe its some sort of drag against the engine, causing it to slow, and having the engine management system raise the idle.
I'm sorry, I should have stated it like this rather than going all around the barn.
Bob
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Question is ..... why does the engine idle at 1100rpm as long as the tranny is in neutral, whether the clutch is engaged or disengaged? Any why does the idle immediately jump to 1200-1300rpm once I put the tranny into first gear?
I'm sorry, I should have stated it like this rather than going all around the barn.
Bob
Round at both ends, and high in the middle - maybe that explains it! :laugh:
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Bob, What you describe is normal on some of the 1200 2V bikes. Seems that the stepper motor senses the load w/in gear not the ecu.
If you pinch off the upper hose from stepper to airbox it all goes away. This is after it is fully warmed. Try it.
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it was rather a speculative question ..... but nothing I really need answered. Just thought someone might have experienced similar issue and would respond. The bike acts this way .... not a big issue.
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Should I come over and mess w/magic screw?
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I think I know where you're going with this ..... we'll talk.
Bob
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Sounds like it has the little switch under the clutch lever like my 09 griso, normal behavior if it has.
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If you pinch off the upper hose from stepper to airbox it all goes away. This is after it is fully warmed. Try it.
I have a pneumatic switch (looks like a normal electrical toggle switch) inserted into this hose on all my 1200 Sports. Stepper motor is allowed to be active when the motor is cold. Another benefit is the increased engine braking noticed when the stepper motor is disabled. Highly recommended.
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Yeah, it's normal. Griso does it too. Not sure about the Stelvio or Norge.
With the Griso, it's built into the map. The ECU senses the clutch in, so it raised the idle about ~200 rpm. So you don't stall you know. :rolleyes: Some Griso maps didn't have that helpful option.
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Yeah, it's normal. Griso does it too. Not sure about the Stelvio or Norge.
No, Stelvio doesn't do that.
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I put another switch in to bypass clutch switch. I thought I would turn it off while in stop & go traffic to elimated the extra rpm. Since I installed it, I never turn it back to normal. The bike runs fine and no added rpm. Easy to drive through campground, parking lots or in traffic.
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I've noticed it on my Stelvio a couple of times. Sitting at a red light, in and out of neutral, notice the revs get a touch higher in gear. Odd, but I ignore it, it is so minor.
It must be something in the code to bump up the idle RPM in gear. They have some reason to do it. Not idea what that is.
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It must be something in the code to bump up the idle RPM in gear. They have some reason to do it. Not idea what that is.
Uninformed newbie perception, it seems logical that some enthusiastic engineer would anticipate measurable drag from transmission and lay code or hardware to instruct the idle circuits to compensate.
If you could please help with the uninformed part, what the hell is a stepper motor?
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If you could please help with the uninformed part, what the hell is a stepper motor?
It's an electric motor which operates in steps over a full revolution. It is used to control, via instructions from the ECU, the amount of additional air that is added to the throttle bodies to assist in maintaining a regular idle.
Many cars have them, but I think MG only uses them on the CARC models. The California 1400 does not have one.
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Stepper is the air feed component in the 'Air over idle' engine speed control system.
The target idle speed is hard coded into the ECU, on the 8V's foe instance resting idle is 1200-1250 RPM. To ensure that this target is met the ECU monitors the engine speed at idle and uses a signal to open or close a variable valve that delivers air to the engine side of the throttle butterflies to enrichen or lean out the mixture.
The leaner the mixture the higher the idle so if the ECU detects the idle speed dropping below 1200 it will open the stepper motor valve allowing more air through and leaning the mixture. If the engine speed gets too high then the ECU will close the stepper enrichening the mixture and slowing the engine speed.
It's primary function is to stabilise the speed during the warm up cycle when the map starts off running very rich and then has a two minute decay curve where it gradually leans out before changing to the main map and running closed loop, the whole input doesn't stabilise though until the engine is running at 60*C. It will also function though to ensure a steady idle at different altitudes/air pressures to compensate for minor inadequacies in the air temp/pressure tables.
One of the commonest complaints about the W5AM equipped bikes which run a stepper is rough idling and 'Surging' on low throttle openings. While this is in part a result of the fuelling being very lean when running within the closed loop portion of the map it is usually greatly exacerbated by poor tuning of the throttle bodies. There is a common fallacy still widely believed that you set up TB's "Just like carbs" and a lot of people who should know better think that you should leave both air bleeds 1 to 1 & 1/2 turns open because "That's the best place for the idle mixture screws on carburettors." Unfortunately this is completely wrong and even if the TB's can be balanced at idle with the screws set thusly it will mean that the mixture at idle and small throttle openings will be far, far too lean and as a result the engine speed will try to race. The ECU will detect this and try and compensate by slamming the stepper closed but then the mixture will go richer and the engine speed will drop suddenly, the ECU panics and once again over compensates by slamming the stepper open so the engine speed will start to race again, hence the 'Surging'. The stepper is only designed to make very fine adjustments at normal operating temperature, if the TB's are incorrectly set up it can't work properly, end of story.
As has been explained many times tuning a W5AM bike is delightfully simple. Set valve lash, ensure air filter is clean, attatch balance tool/vacuum gauges, and connect your diagnostic tooling, start engine and warm to over 60*C. Close both air bleeds fully, (Just snug them down, no need to torque them to a zillion mile tonnes.) then holding the throttle so the engine runs about 3,500-4,000 rpm use the screw on the bell crank on the LH throttle body to get the high speed balance correct.
Once that is correct close the throttle and turn the engine off using the kill switch. Because the TPS is on the right hand throttle body adjusting the linkage rod length via the bell crank screw, (DO NOT, EVER, THINK OF ADJUSTING THE ROD LENGTH ITSELF UNLESS YOU WANT TO END UP IN A WORLD OF PAIN!) will alter the reading of the TPS. Since this is an interpretive reading it has to now be re-set using your diagnostic tool. Once that has been done the engine can be re-started and whichever side has the higher manifold depression at idle? Open the air bleed that side until both are equal.
Turn off engine, re-set the self learning parameters (Trims) to baseline, double check the TPS reading. Disconnect the tooling and plug the vacuum ports, (Or reconnect the evaporative canister tubes if fitted.), disconnect diagnostic tooling. Put seat back on. Go ride!
If one is running a well built open loop map and the tune is done correctly any W5AM bike, even the supposedly twitchy 8V's, will idle cleanly and pull like a freight train from 2,000 RPM with no hunting or surging and should maintain a clean steady idle. The issue with the idle speed picking up a few hundred RPM when the clutch is pulled is peculiar to some maps and is a non-adjustable, hard coded parameter. From memory it is caused by the ECU advancing the spark a bit rather than opening the stepper but I'll let those with a better understanding of the intricacies of the computer's 'Mind' explain that one.
The long and the short of it though is that if your bike is surgy or hunts a lot it is almost certainly down to the fact it simply isn't tuned properly. Probably the easiest check in the world is just to see if both air bleeds are open! If they are then someone has dropped the ball during the tune-up and the poor thing will never run right in a month of Sunday's!
Pete
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[Kiwi_Dave], [Vasco DG], thank you both very much.