Revs dropping below 1000rpm

Hi

My GRiSO has just this morning started to act oddly. At the traffic lights in neutral she stalled. She started up straight away but the idle revs are low, forcing me to gently rev her. Once underway she behaves normally, but when you slow up the revs drop away.

It sort sounds fuel related, so will be check the Air filter for blockages etc, and check the full lines aren't pinched, but I haven't had the tank off so that would be weird, anything else I should check?

Also can anyone tell me why I can find Air filters for the GRiSO ranging from £10 to £60 (GBP) seems madness for me, it ain't a bloody pod filter..

Thanks Guys, appreciate your help.
Simone

SuperSimo wrote:

Hi

My GRiSO has just this morning started to act oddly. At the traffic lights in neutral she stalled. She started up straight away but the idle revs are low, forcing me to gently rev her. Once underway she behaves normally, but when you slow up the revs drop away.

It sort sounds fuel related, so will be check the Air filter for blockages etc, and check the full lines aren't pinched, but I haven't had the tank off so that would be weird, anything else I should check?

Also can anyone tell me why I can find Air filters for the GRiSO ranging from £10 to £60 (GBP) seems madness for me, it ain't a bloody pod filter..

Thanks Guys, appreciate your help.
Simone

There is a stepper motor in the intake that controls the minimum rpm as directed by the ECU. By-pasing the throttles it admits air into the engine.

As above I doubt it is the air filter or fuel starvation but to your question....Gutsibits does kit with plugs, oil filter, air filter plus crush washers for 45 gbp.....they do air filter alone for 8.40 gbp (or you waste 41 gbp on k&n high performance one).

I would check by blanking the stepper motor (golf tees work well or suitable size bolts) as this is couple minutes to do.

After that & depending what map you are running (Lambdas on or off) it could be worth clearing learning parameters and/or checking it isn't lambda problem (just unplug it and see if problem goes away - you will get warning up but doesn't matter)

and check how much oil is gathered in the inlets/airbox :-)

-check inside Tb for dirt.
- what is tps value al idle? should be 4.6-4.8

paper filter is good enough, don't spend to much on that.

@techman-001 & @Paulbrice
Thanks for the info, but I am not sure where the stepper motor is, I can't identify it on the exploded parts diagram, am looking at Blow by assy or Air Box assy? By blanking the motor do you need to block it?
Will check for oil in the inlet too, what would it mean if there is oil there.

@pauldaytona
Thanks for the info too, but I am not sure what the Tb is? Throttle body? and Tps? Throtle position switch?

I thought I was more tech savvy, bit embarrassed but hey this is how you learn and thanks for being my teachers.

It is between the two throttle bodies (need to remove tank to access it BUT you don't need to remove tank to block off the air flow to it). It takes air from the top LHS of the airbox through rubber pipe you can easily pull off and block shut; and it distributes air to the two throttle bodies using smaller rubber pipes you can also clamp or block.  If you find it is the problem then you can try squirting carb cleaner/injector cleaner in to loosen it. Make sure you don't block the blowby rubber pipe into airbox though !. Here is diagram that shows it as item number 20. Can't find diagram with the air supply but will look for that also. [You must be registered and logged in to see this image.]

Just checked to confirm. So the pipe you can see in the diagram that goes to the idle air control stepper comes out the LHS top of airbox (as you sit on bike) and the blowby gas recirculation pipe goes in similar position on RHS (as you sit on bike). I use large flat blade screwdriver to tease the pipe out and then block it (or just put finger over it and see if that solves the problem). Paul

...and if you get a torch and look in between the two throttle bodies (TBs) you will see smaller pipe coming from stepper to inside of TB. You could also clamp or block these to test problem.

There is always lot of oil that gets 'entrained' by the blowby gases and comes through the canister at front (that is supposed to separate it and drop it back to sump). If you open the air box door under the battery you will see oil and if you put smart phone or similar in you can photo back of TB valves...these usually have lots of deposits (thick oil and sludge) around them. One symptom of overfilling oil level is that the oil REALLY gets pulled thru to inlets; and has been thought could cause the high idle but maybe also low idle ??. I assumed the problem came on suddenly but Paul D is right you should check TB position as this could easily screw up idle (and balance the vacuum making sure one air bleed is shut completely - see other threads).

for TPS....there are two throttle bodies (air flow valves inside) which are linked via a rod that MUST NEVER BE ADJUSTED as is set at factory so both valves are synchronised. At closed throttle position these should be 4.6 -4.8 degrees as an input to the ECU as a start position. The 4.6-4.8 is set/reset using the Guzzidiag software and cables connected. This should rarely change but should be checked regularly and redone if you do any work to disturb timing, TBs etc....all in threads on forum.

Learning & doing all this stuff is part of the fun of ownership alongside so much fun riding it/her, so worth getting yourself the gear if you don't already.

This does sound as if it might be stepper related and most stepper issues can be traced back to over filling of the engine with oil and this can be exacerbated by too gentle running in procedures.

Assiduously topping up the oil level to keep it at the 'Full' mark on the stick will result in lots of oil being pumped out into the airbox. If ring seal is poor this is even worse. This oily vapour will not only tend to clog the stepper motor, (Eatlier metal ones were particularly prone to sticking. The plastic bodies ones less so.) but can also coat the throttle plates and throats of the throttle bodies which can cause some, errr? *Interesting* side effects.

Removing the TB's from a GRiSO isn't a big job, some other models it's more of a chore, but giving them a really good and thorough clean off the bike will usually cure a lot of problems. Spraying some carby cleaner through the stepper will also rinse out a multitude of gribblies.

One of the commonest problems is the high idle and 'Spitting back' through the TB's at idle. It's important to understand how dirty TB's will cause this.

When the TB's are new and squeaky clean if the throttle is released the plates will drop fully back to the 'Closed' position. Unfortunately once they get all manked up with grot and oily deposits they won't BUT GENERALLY ONLY WHEN THE ENGINE IS RUNNING!

This presents a real problem when tuning the bike because the TPS can only be re-set while the engine isn't running. So with the engine off the TPS can be observed to be correct or re-set if it isn't and then it appears to be tickety boo and honky dory. The problem is that when you start the motor the air pressure on the throttle plates causes them to move slightly and swivel so with the engine idling the TPS reading is increased to somewhat higher, usually between 0.4-0.5 degrees higher so on a 2V motor it will hop up to about 5.0 degrees and on an 8V as high as 5.2-5.3!

The problem created is that at those sorts of readings the spark is starting to advance but the idle mixture, being controlled by the stepper, remains pretty much as it should be at idle to maintain engine speed so for that speed the spark occurs too early so the mixture sometimes ignites and periodically causes the engine to 'Chuff' and spit back through the TB's. If the mixture goes outside of the range able to be compensated for by the stepper or if the stepper is clogged the result will be an elevated idle speed.

Obviously the only true *Fix* is to remove and clean the TB's and ensure the stepper is working correctly but a temporary kludge can be done as a 'Get me to the next service interval' cure.

Connect Guzzidiag or whatever tool you use and ascertain what the TPS setting is at idle. Say it's an 8V and its reading 5.3. That's about 0.5 of a degree too much. As soon as you kill the engine though the reading will drop back to where it should be at 4.8 though. At that point grab your feeler gauges and insert enough, (Try 2.5 thou first up.) between the throttle stop of the LH butterfly plate and the 'Sacred screw' to raise the TPS reading by that same 0.5 of a degree. Now, without disturbing anything re-set the TPS using Guzzidiag/whatever and then remove the feeler gauge. The result will be that with the engine off the TPS reading will be lower than the required 4.8 but as soon as the motor is started it will rise to 4.8 or close to, not high enough for the spark to start advancing so the spitting back may be mitigated.

As I said this is NOT an alternative to removing and thoroughly cleaning the TB's, it is only a temporary kludge to avoid the high idle until you have time to do the job properly. It's better though than sitting in traffic with the engine revving away like a bastard or it 'Chuffing' every few hundred revolutions at idle.

Main trick though is after you've cleaned everything up and got it working properly again DON'T fill your sump fuller than 1/3 rd of the way up the stick from the 'Add' mark and try and get your rings bedded properly by giving the engine a really good lugging and thrashing!

Pete

So it starts with proper maintenance.

Exactly, and proper running in. None of this 'Ever so gentle' bullshit!

SuperSimo wrote:

@techman-001 &  @Paulbrice
Thanks for the info, but I am not sure where the stepper motor is, I can't identify it on the exploded parts diagram,

Here is another go at clarifying the parts picture of the throttle body. (Someone forgot to lock up the crayons ;-)
* (2) is the TPS or throttle body position sensor, which is a variable resistor (potentiometer.)
* Yellow (20) is the idlle stepper motor
* Green would be the air inlet tube that feeds the idle air stepper valve
* Light blue are the air feeds to the throttle tubes from the idle air stepper valve

Note: I've never worked on these parts but have read on the forum that they can be fragile, so be very careful and don't force anything, especially connectors etc

[You must be registered and logged in to see this image.]

WOW! Thanks guys for the all the helpful information. I love working on my bike, it's a real sense of satisfaction, but with you guys on my side I feel really confident.

Pete.
This issue started after I had the original cams replaced with the new roller cam kits and I probably am running her in very gently, but also becuase I've fitted new brake pads all round and new tyres, so once I bed the brakes in and scrub the tyres can give it some 'welly'? It was -1C this morning, so don't I'll be out in the cold for too long though.

Thanks again, great being part of this awesome forum, hopefully I can help a member soon enough.

Thanks Paul, Paul, Roper, and Tech all this info ,
I'm going to get it tattooed on my eyelids so I remember, I always
Thought more oil is better .
Nev

Awesome Street

So interesting few days in the garage pulling the bike apart. With the information & diagrams in this thread it was so easy.

Here's what I found:
All paths clear, air filter clean, no oil gunk anywhere.
TB's looked ok, but since I had access to them they have been cleaned and carb cleaner squirted through the stepper.
When throttle released the plates close perfectly. (unfortunately I didn't check this before cleaning, rookie error)
I don't have the Guzzidiag or other diagnosis tool, maybe I should get one though. I put it all back together and filled up with fuel (97) none of that Ethanol stuff and rode 40miles in the rain without any issue. I'm happy, but not sure what fixed the issue. Hopefully this weekend can get a longer ride in and see what happens.

Thanks again for your help. You guys rock!

You don't have to 'Buy' Guzzidiag, (but if you don't give something back you're an arse.) all you have to buy is a couple of cables that will set you back twenty quid and the use of an old 'Beater' laptop.

Without a computer you can't tune a W5AM Guzzi. The good news is if you conquer your fear it's easy as falling off a log.

Pete

SuperSimo wrote:

So interesting few days in the garage pulling the bike apart. With the information & diagrams in this thread it was so easy.

Here's what I found:
All paths clear, air filter clean, no oil gunk anywhere.
TB's looked ok, but since I had access to them they have been cleaned and carb cleaner squirted through the stepper.
When throttle released the plates close perfectly. (unfortunately I didn't check this before cleaning, rookie error)
I don't have the Guzzidiag or other diagnosis tool, maybe I should get one though. I put it all back together and filled up with fuel (97) none of that Ethanol stuff and rode 40miles in the rain without any issue. I'm happy, but not sure what fixed the issue. Hopefully this weekend can get a longer ride in and see what happens.

Thanks again for your help. You guys rock!

Well done, perhaps it was the carb cleaner, or the energy of a dedicated mind ?

Re the free Guzzidiag, all you need is a pc/laptop running Linux or windows, a dongle and a adapter cable.

The Grisoghetto recommended dongle and cable is this one, which is quite affordable at  £22.99 :-
Lonelec dongle and cable

I bought this one from Lonelec, who dispatched promptly and professionally.

It worked fine on a friends Guzzi but not my GRiSO but I eventually found that my GRiSO diagnostics plug was not wired correctly and now it all works like a charm.