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My Stelvio coughs on overrun and does not like idling!


LangleyMalc
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Hi guys,  

Ever since I got my 2013 8V Stelvio last year it has had a tendency to cough on overrun and was a lumpy idle.  I changed the map to one from Beetle and that improved it and smoothed out the performance overall, and at the same time I re-set the low speed balance as per the instructions etc., but it still does it and while it will idle when cold, once it gets hot, or idles for a while, (around 1100 revs) it tends to try to drop a cylinder, so I have to keep a hand on the throttle at the stop signs and goose it occasionally.

I read on another site about someone having a problem on a 1400 Cal., with too much oil in the crankcase leading to oil in the air box and ultimately on the Lambda sensor on a 1400.  Pete R. had warned me to only fill the crank to ⅓ of the dipstick and I did that, but when I checked in the airbox, there was a bit of creme in the right hand cylinder intake trumpet, but minimal oil in the box itself. 

None of this is a major problem, but I would like to cure the problem, rather than simply turning up the slow running and ignoring the minor amounts of spitting on over run.  So first off where is the lambda sensor on this bike and how do I clean it and is this a likely culprit?  Otherwise what else should I be looking at?

Thanks in advance.

LangleyMalc

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You mentioned installing a Beetle map, iirc all of his maps have the lambda turned off, so I don't think that should be an issue.

Have you done a basic tuneup ie, valves, tps, balance and trim?

I know some of the CARC bikes were known to have problematic oem plug wires/caps, mainly from owners pulling on the caps rather than prying them up gently, you may want to verify if that's a known issue with your Stelvio. 

That's all I've got, fwiw

good luck

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OK, by a 'Basic tune up' what exactly did you do? If you balanced the throttlebodies? How? What was the sequence? Did you try and change the idle speed by moving the throttle stop screw/s? Did you re-calibrate the TPS after the balance?

When the plug caps were removed to set the valves how was it done?

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At the risk of boring the assembled multitudes of MG cognoscenti and having you all repeat yourselves, I bought this bike from Eastern Canada to ride it back across to the West coast, but could not collect it as planned because of Covid and the Covid bubble in Eastern Canada etc.  As a consequence, I eventually had it shipped across to BC.  When I bought it the dealer did an oil change etc before he shipped it.  When I got it, I took advice from the aforementioned cognoscenti and  checked the rear shock linkage, or dog bone, (dry as a bone and with rusty bearings, so replaced it) and subsequently rode the bike for a while.  It went fine, but its one habit was to spit or backfire on overrun, when the throttle was shut using engine breaking. Note that my Cal 1400 does not do this!

As a consequence I decided that I should go through the bike and add a new map from Beetle.  So I did the valves as per the instructions on the web by I think Pete R.  To do this I was careful to pull the valve caps with long nose pliers so as not too damage the cables.  I then added the map from Beetle through Guzzi Diag.  Finally I reset the TPS and balanced the throttle bodies on idle using a set of Carb sticks.  I did not touch the link between the two throttle bodies as this was highlighted as something not to do in the web narrative.  Did I do it all correctly?  I hope so, but there is no guarantee.  This despite the fact that I am an anally retentive retired mining engineer with enough mechanical knowledge to be dangerous.

I also changed the rear shock for a Matris and had the front cartridges changed to larger Andreani.  The end result is a bike that handles beautifully and is a pleasure to ride apart from the aforementioned spits and the lumpy idle.  So the bike now runs fine on the open road apart from STILL spitting on overrun, but not as bad as it used to before remapping; plus it has a poor idle.  

So rather than lurching my way through the problem, what I am looking for is a simple analysis along the following lines:

  1. What causes the spitting or backfire on overrun?  It was there when I got the bike and before the re-map and before I rebalanced the Throttle bodies and did the TPS etc.  I would have presumed it was too lean with the throttle closed - but what do I know?
  2. Is this two problems? First the spitting on overrun and second the lumpy idle, or is it more likely a single cause?What typically causes a poor idle?
  3. Could it be that one of the plug leads has been damaged?  Either by me or by the prior owner?  does this cause a poor idle as discussed?
  4. Does the Beetle map use the Lambda sensor?  if not, there is not much point in pulling it and cleaning it.
  5. What else should I be thinking about?

My next steps now that Autumn is here will be to service the bike for winter - oil change, reset tappets and then consider resetting the TPS and balancing the Throttle bodies etc.and try to sort out the spitting and Idle.  So at the risk of repeating myself, where should I start?

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OK, firstly you NEVER use pliers on the plug caps of an 8V. To remove the caps you use a long, thin, flat bladed screwdriver poked in through the cooling tunnel above the exhaust manifold in the head and lever them off from underneath. Any sort of twisting or tugging at the tops of the caps is almost certain to cause damage and the spark will then arc to the rocker cover or plug tube preventing the cylinder from firing. This causes a host of problems beyond just stopping the cylinder firing. Unburnt fuel can cause the Catalyser to catch fire or clog and prevent the engine running correctly. Check and/or replace the caps. Use NGK SB05E or F plug caps. The E or F suffix denotes the type of top electrode on the plug. This is cheap and easy. Checking for arcing is best done by removing the plug lead covers on the rocker covers and watching and listening for the spark *Snapping* to earth. Do this after dark preferably, it makes the sparks easier to see.

Your question about oil fouling *Something* would not effect the lambda sensor/s. The thing you are thinking about on the 1400 is the MAP, (Manifold absolute pressure.) sensor in the airbox. The W5AM system does not use a MAP sensor. Oil fouling can cause problems but not this one.

If you are running a Beetlemap any odd behaviour on the over-run above 2,700 rpm is not related to fuelling as the fuel is turned off above this point at <5* TPS value. When the fuel cuts back in at that point it can cause a single small 'Pop' unless you are running an open pipe in which case it will pop and bang a bit and the fouling won't be very good anyway as none of Mark's maps are built for open pipes or noisy morons.

The lumpy idle could well be damaged plug caps or incorrect throttlebody balance or, worst case scenario, monstered throttlebodies. I guess I'll have to take some pics showing what TB's should look like and which screws you can and can't touch. For some reason I can't post pics easily on this board but the mods usually help me out.

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10 minutes ago, pete roper said:

OK, firstly you NEVER use pliers on the plug caps of an 8V. To remove the caps you use a long, thin, flat bladed screwdriver poked in through the cooling tunnel above the exhaust manifold in the head and lever them off from underneath. Any sort of twisting or tugging at the tops of the caps is almost certain to cause damage and the spark will then arc to the rocker cover or plug tube preventing the cylinder from firing. This causes a host of problems beyond just stopping the cylinder firing. Unburnt fuel can cause the Catalyser to catch fire or clog and prevent the engine running correctly. Check and/or replace the caps. Use NGK SB05E or F plug caps. The E or F suffix denotes the type of top electrode on the plug. This is cheap and easy. Checking for arcing is best done by removing the plug lead covers on the rocker covers and watching and listening for the spark *Snapping* to earth. Do this after dark preferably, it makes the sparks easier to see.

Your question about oil fouling *Something* would not effect the lambda sensor/s. The thing you are thinking about on the 1400 is the MAP, (Manifold absolute pressure.) sensor in the airbox. The W5AM system does not use a MAP sensor. Oil fouling can cause problems but not this one.

If you are running a Beetlemap any odd behaviour on the over-run above 2,700 rpm is not related to fuelling as the fuel is turned off above this point at <5* TPS value. When the fuel cuts back in at that point it can cause a single small 'Pop' unless you are running an open pipe in which case it will pop and bang a bit and the fouling won't be very good anyway as none of Mark's maps are built for open pipes or noisy morons.

The lumpy idle could well be damaged plug caps or incorrect throttlebody balance or, worst case scenario, monstered throttlebodies. I guess I'll have to take some pics showing what TB's should look like and which screws you can and can't touch. For some reason I can't post pics easily on this board but the mods usually help me out.

Load images into your album Pete then just "copy image" from there and paste into your post. Thats what I do.

Ciao 

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I seem to have problems getting them to size right Phil, that's the biggest issue. I just get told they're too large, no matter what size I try and make them. Probably just me having a 'Senior's Moment'!

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5 minutes ago, pete roper said:

I seem to have problems getting them to size right Phil, that's the biggest issue. I just get told they're too large, no matter what size I try and make them. Probably just me having a 'Senior's Moment'!

If you upload to your album the size is irrelevant. I never resize when using the way I described. Don't open the image from your album just "copy image" from the album and paste in your post. I open a separate browser for the "copy image" and then switch browsers to the post browser and paste. 

Ciao

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Thanks for the detailed replies. Sounds like the first step is a trip to the garage after dark to “observe” the plug caps. Then potentially replace both to eliminate that problem. 
After that tappets and then check the TPS and tune with Guzzidiag, then set slow running, then re-sett TPS. Then re check for problem, or ride away with a big shit eating grin and congratulate myself on my intelligence for writing to you lot!

Somewhere on here was a complete “How to” for this sequence. Anyone remember where?  With the state of my memory nowadays I am reluctant to leave it to what i thought i did last time!

Thanks in advance. 

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Tuning sequence for a W5AM is ridiculously simple.

Connect manometer and Guzzidiag, (Or whatever diagnostic tooling you use.)

After you have set the valve lash to 4thou inlet and 6thou exhaust warm the engine up to >60*C and close both air bleeds.

Hold the throttle open so the engine runs at 3,500-4,000 rpm and using the screw on the bell crank on the LH throttlebody balance the manifold depression at 'High Speed'.

Once done let the throttle snap shut. Kill the engine with the kill switch and recalibrate the TPS and clear the self learning parameters, (The acquired fuel trims. This is only really necessary if running a closed loop map but just do it anyway.).

Restart the motor and whichever side has the higher manifold depression? Open the air bleed on that throttlebody to restore equilibrium.

Thats it! That is all there is to tuning a W5AM Guzzi, (Bellagio excepted.). Do NOT try and change the idle speed by messing with the throttle stop screw to close the butterflies of the TB's. The idle speed is hard coded into the map in the ECU and is controlled by an air over idle system with a mechanical air bleed called a stepper motor that stabilises the idle at its 'Target' by adding or subtracting air to influence the idle speed. This is also controlled by the ECU. The 'Target Idle' is adjustable but only within the map using a program like Tunerpro to manipulate it once it has been downloaded from the ECU. Once modified the new map has to be re-uploaded to the ECU. This shouldn't need doing if the bike is mechanically sound and tuned properly.

There are few bikes easier to tune than a W5AM Guzzi. It probably takes about the same time as it took me to write this message.

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Thanks for this Peter.  It will likely be later in the month before I get around to doing this and I have to nail my grandson for his older windows computer to run Guzzi Diag!  We are now solidly into Autumn, but for your delectation I would have included a picture of the White Pig (Cal 1400 bagger) on a run up to Whistler in the Coast mountains today; but like you I could not get it to reduce below 200K!  Weather was spectacular and worth the trip, particularly as this will be towards the end of the riding season with snow on the hills.

Ill keep you posted on the Stelvio and follow the instructions to the letter.

Regards

Malcolm

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