Missing, sputtering, whatever below 3K

[slug]

So I'm over on the east side of the state for a few days visiting family and what do you know... Heat wave... Temperatures the past couple of days have been in the upper 90's to low 100's. Personally, I like it, but it seems like the bike doesn't, at least that's my best guess.

 

What's happening is that the engine semi-frequently hesitates, misses, lurches, maybe even pops a bit when below 3K rpm, especially when it's under a light load. Above that it's fine since I usually try to keep it above 3500 rpm, but when slowing down to go through small towns it's a bit unnerving.

 

Here's the setup:

 

'04 Ballabio with:

 

- Guzzi Ti pipes w/race ECU.

- Stucci X-Over.

- Stock intake & filter.

- Stainless x-over shims up front

- Old style fuel tank w/external pump, mounted on the side of the spine.

- Always run 91 - 92 octane fuel.

 

Intake boots look to be in good shape and throttle bodies seem to be mounted fine.

No obvious exhaust leaks at the headers or x-over.

 

I have a brass temp sensor housing which I plan on mounting this week when I get back home...

 

It wasn't doing this when it wasn't so hot... Any ideas? Many thanks!

[Tom M]

Assuming your TB's are balanced, valve lash is in spec, and TPS is set correctly, my only thought is you might be a little lean with the non-stock crossover. I suppose you could tweak the TPS a bit (15mV?) to richen it up abit across the board. If you don't like the result set it back to where it was.

[Ouiji Veck]

Normally I suspect TB sync for sputtering / farting @

low throttle / decelerating but if it's started all of a sudden

I'd more suspect something gone off it's moorings.

Especially the boots but you say you've checked them.

Give the plugs a look. Check the color and if they match.

I Don't know if the temp sensor can go wrong with the heat and

lean it out too far.?? Mine was never bothered by the heat and I've

pushed her pretty hard for long periods of time in 95+ temps.

 

Good luck. I'll be curious to see what the solution is.

My moneys on a boot or just plain TB sync.

Check your valve lash and maybe TPS first... like Tom says.

[Bbennett]

For waht its worth, I was experiencing the very same thing in very hot weather and I noted I had very little fuel in the tank. When I filled her up, the sputter at low RPM problem seemed to go away - making me wonder if I either had bad fuel or somehow the heat from the engine at low speeds/RPM was causing issues. We will see if the bike is really better if the temperature gets hot again today.

[droydx]

My 03 Rosso had exactly the same problems. This is my experieince, YMMV: I tuned it, synched, valves, TPS adjusted, no air leaks on intake or exhaust, but still a pop/stutter at about 3K RPM throttle at 5-15%. Mine would be fine cool, and then act up when operating in warm/hot conditions. I have a Power Commander running a map down loaded for a bike with an FBF open air lid, Stucchi X-over, and Mistral Ti ovals. I finally decided to richen up the mixture in the "Pop zone" and voila! No more pop...solid pull through 3000 - 4000, and able to crawl in traffic in 1st gear without bucking and snorting!

 

 

 

Andy

[slug]

Thanks everyone. I'll poke around a bit more, though there's not much I can do since all my tools are 170 miles away.

[Dan M]

I have a Power Commander running a map down loaded for a bike with an FBF open air lid, Stucchi X-over, and Mistral Ti ovals. I finally decided to richen up the mixture in the "Pop zone" and voila! No more pop...solid pull through 3000 - 4000, and able to crawl in traffic in 1st gear without bucking and snorting!

 

 

Andy

 

Andy,

Just curious, how much did you enrich those rpm/throttle zones? +5? +10? More?

[Fast Willy]

I had the exact same problem with my 2003 Lemans. I just went up two bars on the manual richening of the power commander using the low button. You have to hold down all three when you turn the key to gain access to the system. Runs very smooth.

[raz]

This is remotely related, but I'm in the mood for writing

 

I've been experimenting quite a bit lately with closed-loop targets for the MyECU. It took me a while to realise how rich you need to run it below 3500 rpm. We're talking at least 12.5:1 and even down to less than 12.3:1 AFR before all and every Italian Sneezes (stumbles) are gone and forgotten. And that is more or less completely without load, which is what was hardest for me to digest. Just crawling in congested traffic. One HP would be enough. I guess the engine simply does not breath well below 4000.

[droydx]

Andy,

Just curious, how much did you enrich those rpm/throttle zones? +5? +10? More?

 

I noticed that all the settings were minus (-) 10 to 15 in that area. I enriched the mixture +10 throughout the 2750 to 3500 range.

 

Andy

[emry]

Ok, I am in the same boat, backfire at idle, off idle stumble, surge at low throttle / rpm settings, but only in the afternoon. Riding to work in the morng never a problem. Seemed to be a lean condition. I have begun to use it as a commuter, 26miles takes me about 1.5 hours. So I am spending a lot of time in traffic, with Atlanta weather around 90-100 F. It gets pretty hot.

 

I checked all the usual suspects, TB sync, TP angle, new plugs, valve clearence, intake boots, etc. Checked the intake air temp and engine temp (has the brass fitting) and their values seemed to be correct, responded to temp changes etc. Replaced the relays. (headlight relay took a dump one day, so it was a good opportunity. Kudos to Dan, great price and ultra fast shipping!!!!)

 

Hooked up a CO meter, and the values were all over the place. 4.5 CO at idle, 0.2 CO at 2k, and 5.6 CO at 4k. This is unloaded.

 

After playing awhile , TP adjustment with it running and re-syncing, I shut it off. I got my gear to take it for a ride, and low and behold no start. Vapor lock!!

 

So I am going to hook up a pressure gauge today and ride home and see what it does. Maybe a weak pump or just to much heat soak from the traffic. Will report more as it occurs.

[Dan M]

Ok, I am in the same boat, backfire at idle, off idle stumble, surge at low throttle / rpm settings, but only in the afternoon. Riding to work in the morng never a problem. Seemed to be a lean condition. I have begun to use it as a commuter, 26miles takes me about 1.5 hours. So I am spending a lot of time in traffic, with Atlanta weather around 90-100 F. It gets pretty hot.

 

I checked all the usual suspects, TB sync, TP angle, new plugs, valve clearence, intake boots, etc. Checked the intake air temp and engine temp (has the brass fitting) and their values seemed to be correct, responded to temp changes etc. Replaced the relays. (headlight relay took a dump one day, so it was a good opportunity. Kudos to Dan, great price and ultra fast shipping!!!!)

 

Hooked up a CO meter, and the values were all over the place. 4.5 CO at idle, 0.2 CO at 2k, and 5.6 CO at 4k. This is unloaded.

 

After playing awhile , TP adjustment with it running and re-syncing, I shut it off. I got my gear to take it for a ride, and low and behold no start. Vapor lock!!

 

So I am going to hook up a pressure gauge today and ride home and see what it does. Maybe a weak pump or just to much heat soak from the traffic. Will report more as it occurs.

 

I've seen similar CO readings. Fueling at idle is always pretty rich. I've gotten a good idle at as lean as 3% but much leaner and it is unsteady. At 2500rpm and above (unloaded) it cleans up nicely and stays in the 2% range. (Oh for the want of a dyno to check it loaded) I too get the 3000 rpm hiccup in really hot conditions. I'm going to try to enrichen that band some with the P.C. as Andy suggested.

[Skeeve]

This is remotely related, but I'm in the mood for writing

 

I've been experimenting quite a bit lately with closed-loop targets for the MyECU. It took me a while to realise how rich you need to run it below 3500 rpm. We're talking at least 12.5:1 and even down to less than 12.3:1 AFR before all and every Italian Sneezes (stumbles) are gone and forgotten. And that is more or less completely without load, which is what was hardest for me to digest. Just crawling in congested traffic. One HP would be enough. I guess the engine simply does not breath well below 4000.

 

Big valves + lumpy cam = poor low end combustion.

 

I know: let's get Honda to design a vvt system for us!

[dlaing]

This is remotely related, but I'm in the mood for writing

 

I've been experimenting quite a bit lately with closed-loop targets for the MyECU. It took me a while to realise how rich you need to run it below 3500 rpm. We're talking at least 12.5:1 and even down to less than 12.3:1 AFR before all and every Italian Sneezes (stumbles) are gone and forgotten. And that is more or less completely without load, which is what was hardest for me to digest. Just crawling in congested traffic. One HP would be enough. I guess the engine simply does not breath well below 4000.

I have been getting heat related popping below 3500, mostly around 2500.

AFR was between 13.0:1 and 13.5:1, but when it popped it would spike lean.

I tried readjusting valves, idle, balance, and checked TPS. I discovered a small leak in the intake manifold rubber throttle body mounts, where they meet the aluminum intake manifold, but sealing it made little or no difference.

So, I moved on to remapping.

I kept gradually enriching and it got better, but not perfect. I was fearful to go below 13.0:1, but your comments lean me towards believing it is necessary.

Also I found an interesting lean spot at 1500 RPM. It runs rich at 1300 and 1700 RPMs, and my Tuneboy fuel cells are at 1300 and 1700, so to enrichen at 1500 I made it even richer at 1300 and 1700.

Another thing I did that seemed to help was change the engine temperature modification so that it runs less rich when still warming up, and less lean when running hot. But I only made subtle changes.

 

I think at 45,000 miles I am ready for a new chain tensioner.

Luigi's VVT works more and more on chaos theory, the more worn it gets

[emry]

Well, I did not run the fuel pressure gauge. I instead opted install a new fuel filter and recheck the TP & sync. Got everything on and set the TP to 545 mv using the method in the "How to." I was rewarded with 0.19 CO at idle!!! Oh that is too lean, so I bumped the TP to 615 mv which took got it back to about 2.5 CO. Still to lean but I though I would try it.

 

Barely made it out of the parking lot. Out came the allen key and I unscientificly nudged the TP father open. Rode a little. Nope not enough. Repeat. Repeat. Finally got it to stop. Rode home no issues.

 

This morning it ran great coming into work, didn't miss once.

 

I have not had a chance to check what the mv ended up at but I am guessing it is close to 900 mv. It will probably be a few days before I can check the CO too.

 

Clearly something is amiss. I will also scope the TP sensor to check for drop offs.

 

Everyone have a Happy & Safe Holiday (here in the US at least), and Cheers to the rest of you!