V7 850 (2021) - unstable cold idle + hard hot start

[huspec]

Hi all,

2021 V7 850 cca 19k km, Mistral exhaust, otherwise stock. I've been chasing a starting/idle issue. I hope I'm not offending anyone here with my amateur attempts, but I've tried to do everything I can manage on my own. 

Cold start, two cases:
- Case 1 (roughly 1 in 10 starts): shortly after starting, the idle fluctuates between cca 1000 – 2000 rpm and then the engine stalls after about 5 s.
    - Video 1 (stall): https://youtube.com/shorts/lNYJk7nMIvM?feature=share
- Case 2 (almost every start): engine starts and runs, but the idle fluctuates cca 1000 – 2000 rpm for about 30 s before it settles at cca 1300 rpm. Blipping the throttle while cold makes things worse, not better.
    - Video 2 (idle hunting): https://youtube.com/shorts/zTfKNS1J0Uc?feature=share

Hot start - after a short stop (5–15 min), roughly 5 in 10 starts:
- This is how the problem initially started.
- Starter cranks normally but the engine doesn't fire. Occasionally I get 1 – 2 backfires/pops in the exhaust.
- I crank for about 2 s, stop, wait a few seconds, then try again and it starts instantly.
- If I open the fuel cap before a hot start, there's an audible pressure release and then the engine starts on the first crank. But I did that only twice so it deserves more tangible testing.

Once running and warmed up, it runs perfectly — power, acceleration and idle are all fine. No fault light, no permanent stored codes noticed.

What I have checked:
- Rides perfectly when wamed up.
- After starting and warming up, idle holds steady around ~1300 rpm with no issues.
- Scanned over OBD — no stored fault codes.
- Spark plugs replaced ~8k km ago (iridium, should basically live forever), valve clearances set ~6k km ago.
- Couldn't find any false/unmetered air being drawn in anywhere.
- No pinched or kinked hoses.
- A small amount of oil in the airbox, but only minor.
- Haven't taken the EVAP system apart yet, but the solenoid does react to 12 V.


I tried measuring the resistance of the NTC thermistor on the engine block. It behaves oddly: the sensor isn't dead, it does return values that change non-linearly as the engine warms up, so it "looks" functional. But the readings don't match the reference table in the manual. I measured the temperature each time on the cylinder head using IR. I park in a garage at a constant temperature, so in the morning the sensor temperature matched room temperature. Even so, the values are off by a fair margin, see my converted table https://docs.google.com/spreadsheets/d/1oNGzjj67ZHo5sHznkaFt6Ql6thhUr7W0FKdrtR6pRbk/edit?usp=sharing

For instance: at an ambient temperature of 24 C I measured 5.3 kOhm, which corresponds to about 13 C as seen by the ECU, so the sensor reads roughly 11 °C colder than reality.

1. I’m not sure I can fairly compare against the manual's reference table. Does anyone have historical resistance-vs-temperature readings from their own NTC sensor? Is mine actually faulty, or do even healthy bikes show this much deviation from the book figures?
2. Any app recommendation for reading the engine temperature live? I have an ELM327. I also have an right KKL cable, but I'm guessing these adapters won't connect through GuzziDiag,  or has anyone gotten an GuzziDiag to talk to the MIU G4 ECU? What app/setup do you use?
3. Could a bad NTC thermistor also cause the hot no-start, or am I looking at two separate issues — a faulty sensor and an EVAP/tank-venting problem?
4. How can I test the EVAP system myself? How do I check the diaphragm/safety valve, and how do I verify the canister is working? Any way to confirm the purge solenoid is actually opening (beyond just reacting to 12 V)?
5. Any other things I can test/inspect myself

Thanks in advance for any help or advice

[malik]

My 2014 V7 Special (165,000km) has always been sensitive to the cleanliness of the air filter & airbox. DO clean out the airbox - paper towels & throttle body cleaner & also down the manifold as far as you can get. ( a squirt of MAS sensor cleaner can't hurt either should you have it handy). Try a new filter in there & re-set the ECU  - leave the negative terminal off for 15 - 20 minutes). Test ride.

Note:- the stock filter works best.

The target idle of the MIU G3 of 1340rpm always & still FEELS uncomfortably high after the V7C 's idle of 1100 rpm.

[Vagrant]

You already did a great job of checking things. Even though the 21+ don't kick oil into the air box like the old ones never fill the oil past the 1/3 between the low and high dipstick mark. Screwed in dipstick after ten minutes of sitting after at least a few miles of running and sitting level. PIA but critical.
My 2020 v85 started up and down  idle (surging) about 1300-2500 while cold at about 4000 miles and never quit. Warm it was fine.
As stated reach up in the rubber boot going to the throttle body and if there is oil residue spray with mass air sensor cleaner only. I do it while running. Trying to reset the computer by taking off both cables from the battery, hold them together then turn on the key and activate the brake light to drain any left over juice. I usually let them sit over night after. I suspect there is at least one new map for it and it might be worth having a good dealer reload it if the above doesn't fix it. 
The hot, refuse to start happened to several of my v7's. If left in the sun. Releasing the pressure always seemed to cure it. If it gets too old then a modification the the vent/tip over valve is in order. Search here and you should find the instructions. But you will get some gas fumes in the garage when hot.

[huspec]

Thanks for the messages. Cleaning the mass airflow sensor is completely new to me, I’ve already ordered a product. How exactly do you clean it? Do you just spray a certain amount through the intake while the engine is running?

I also change the air filter every time I change the oil, so about every 7,000 km, and I always use the correct UFI filter, so that should be fine. Some oil got into the airbox during the first service. I followed the manual and used the specified amount (1750ml), which was at the upper limit. It turned out to be too much. Now I know it’s better to stay below that level and check it more often.

I also found on the forum that the entire EVAP system can be removed, but that seems like a pretty radical change. I’d rather first identify whether there is actually a problem in the system. I just don’t really know how to check it other than buying a new canister + purge valve and swapping them to see if it helps.

Today I also checked temperatures via OBD: the room was 24 C, the bike’s ambient sensor showed 24 C, and the engine temperature via OBD also showed 24 C. But at the same time, I measured 5.18 kOhm, which (according to reference conversion tables) should correspond to about 13 C. So I’m not sure what to trust. The OBD app is just some generic mobile app, could it be reading wrong?

Also, is fluctuating idle RPM on startup something I should be concerned about?

[Vagrant]

JMHO.
Your wasting a lot of time and money on air filters unless you drive gravel roads every day. If in clean air there is only one reason to change before 40000 miles and that's to piss away $. Again, JMHO.
I'd just ignore the hunt and peck idle as long as you are sure there are no air leaks. Check to see if all the rubber boots from the cylinder head back to the air box are fitted in place and snug. If it has screw clamps snug them up. If they seem so then while the engine is running spray a bit of carb cleaner or WD40 around them and as long as the idle doesn't change you should be good. Sometimes the factory doesn't get them seated right or they get knocked out of place. If the gas tank has been off you could have pinched the vent line. Sometimes the anti spill/vent valve goes bad or only works when straight sideways or up and down. I don't remember which. I never removed mine from my last 7 small blocks 2016-2026 because I had no issues. I do remember some bitches on the 21 v7-850 though. It was discussed a lot on the ADVRider v7-850 site.
https://www.advrider.com/f/threads/moto-guzzi-v7-850.1486696/page-159#post-55021887
back track or search here.

[Dirk_S]

Make sure these screws securing the injector covers to the intake manifolds are seated properly on both sides. I think these threaded holes still go all the way into the intake, so there’s a chance there could be a leak:

[Kev m]

I also found on the forum that the entire EVAP system can be removed, but that seems like a pretty radical change. I’d rather first identify whether there is actually a problem in the system. I just don’t really know how to check it other than buying a new canister + purge valve and swapping them to see if it helps.

<snip>

Also, is fluctuating idle RPM on startup something I should be concerned about?

TOTALLY SIMPLE way to test if the EVAP system is a problem. Clamp the purge line from the EVAP canister to the throttle body shut and start the bike. If the systems repeat with the line clamped, IT'S NOT THE EVAP. If the systems were intermittent in the first place you may have to repeat the test at least a few times (unless they come back right away and then you know you can move on).

As for concerned? It depends. I have a 2013 MKI MUIG3 throttle body V7 Stone in the fleet that I bought new.

From day 1 it has had a cold idle stumble where MOST cold starts (especially in warmer or more humid temperatures) result in a fluctuating idle and a bike that stalls if you put it in gear and try to ride away within the first minute. If you just leave it alone for a minute or two it will be fine and I can ride away and probably not experience it the rest of the day, even after stopping for lunch or something.

NO ONE has been able to figure it out. Not Eraldo Ferracci (who sold me the bike new when he still had a dealership and not just a accessory/race shop), not gurus from this forum, and honestly even Beetle told me that IF that was my only concern I should probably just live with it. Which I have done for what will be 14 years this Nov.

It's weird and I've not experienced it on any other bike, including my 2018 MKIII V7, nor on any other V7 or V9 I've ridden since.

* shrugs *

It sounds a little different from yours and if you can find a solution, great. But if it's only on intermittent cold starts - * shrugs again *

[Vagrant]

Kev, I had that cold ride off on the 15 and 16 v7's. I sold the 15 that way but a Beetle map fixed the 16. Spend the $100 it's worth it. He really under sells his work.

[Moparnut72]

My '26 Special has a rough idle when first started. It would surge for a minute or so after taking off. I eliminated the purge valve which fixed most of it. It will still surge a little upon first start but would settle down after a minute or so. I put my gear on after starting and it will be fine by the time I am ready to go and I can ride off smoothly.
kk

[Kev m]

Kev, I had that cold ride off on the 15 and 16 v7's. I sold the 15 that way but a Beetle map fixed the 16. Spend the $100 it's worth it. He really under sells his work.

14 years living with it ... It's not about the $100, it's about how perfectly it works the other 99% of the time. But I get it.