Been having this issue for a while and I'm at the point I don't know what to try next. The setup is in sig and link to the Hondata forum post I made is below.

I get a random part throttle (roughly 12-20% TPS) stumble during low load cruise. It doesn't happen all the time but seems to occur more in warmer conditions or if I have just run the car hard. The car runs great at full throttle (no breaking up).

I was able to finally get a great datalog of the problem (both available in the hondata link below).

MAP/TPS are within a few % between no stumbling and stumbling and ECT/IAT/timing are the same. Fuel table looks good. My wideband goes lean and the S trim goes nuts maxing out and trying to add fuel. Then the A/F and S trim start to oscillate and I assume that's the stumbling. I can't figure out why it is happening. I'm not seeing any strange TPS/MAP spikes and fuel pressure remains solid. Going to try a known good ECU tomorrow. Car was just tuned so I don't think its the tune.

Hondata forum thread link -> http://www.hondata.com/forum/viewtopic.php?f=19&t=17333

 

You need to eliminate the intersecting lines in your fuel and timing maps.

Also disable lean protection 1, it is set to 14:1 under light throttle and is unnecessary.

 

Thanks. I really appreciate the help. I will do that tomorrow and report back.

 

You should posta screen shot of the maps I cant see them if im not a member over on hondata.

 

Do you have S300? I could email you the data.

 

I can't remember but does the s300 have a baro sensor? it could be causing issues

also the lean protection could be the cause of the whole thing

 

Some have it and some don't. There is a setting to disable it.

I will check the lean protection first. I don't think I have ever messed with those parameters but I will give it a try. I also know that the lean protection was bugged in Smanager version 2.2.7.0. I believe it wasn't working in that version (which is the version I have been running).

 

hatch96y7@yahoo.com

Shoot It over

 

hope this fix your trouble so you can help me out with the cpr install.. lol

 

Email sent. I included the cal and the datalog.

 

LOL!

Yeah, I'd like to get the CPR install going. I'm not sure how I'm going to get the plug through the firewall tho. I think it's too big to pass through the pass side hole near the battery.

I'd rather not cut a hole in the firewall but may be only way.

 

yea I was thinking same thing imam pull the catch can tomorrow and really look at it worse come to worse I guess hole and grommet from lowes.

 

I changed that lean protection value but I don't think it is the issue. It was set for 2 psi and the issue I'm having is occurring in vacuum (negative teens to be exact) not positive manifold pressure.

As for the fuel/timing where the stumbling is occurring is not in an area where lines intersect. I will work on cleaning those areas up to see if it helps.

Thanks again.

 

Probably a fuel map issue. Most tuners do not properly tune the engine at low load cruise condition because it takes time and time is money. It takes many hours of road tuning to set a tune just right in the vacuum condition, wot tuning is fast.

 

That is true but with this particular problem the fuel tables look good where it happens. Also it won't always happen even under the exact same conditions.

For instance I was driving around for a while this morning and could not get it to happen even though I was in the area of the map where it happens.

I did make the timing/protection adjustments suggested above b4 I went out, but I have no way of knowing if it is fixed unless it happens again.


I really do appreciate everyone's thoughts/ideas.

 

I took a look at your 1/2 hr datalog ant it looks like the S trim is very aggressive. It is cycling way too fast suggesting injector or misfires issue. The resultant AF have lean spike and the ECU is chasing it (S trim).

Also at idle your S trim is at -25% so the fuel map should be adjusted to a more appropriate -5%. This would minimize the amount of work the ECU has to do to the s trim correction going from idle to cruise.

I think the O2 voltage the ECU sees at idle is noisy. Could be a grounding issue. Can you try a different WB?

 

It does feel like it misfires on occasion. I can't say it is, but it feels like it. When I first started chasing this problem I replaced all of the ignition system with OEM parts (distributor, coil, ICM, cap, rotor, plugs, wires) because it was misfiring at times on the dyno. The thing is, if it were a misfire wouldn't it be more prevalent under load? It has no issues under load and in boost.

I have been working on the idle/part throttle fuel trim. This was right after the tune and the tuner made significant changes so it threw off part throttle. I'm have since got the S trim to where it hovers a lot closer to 0, thought it still does sweep a bit. Worth noting that it was doing this long before this tune was done.

I don't have access to another WB but I will happily check the wiring tonight. The sensor is less then 2 years old but it isn't showing signs of the sensor failing.

 

It is normal to have a misfire at low load when the AF go into the 16 because a lean mixture is harder to ignite than a rich.

In your log, at 19min45s I can see the AF go past 16.5AFR and the s trim reaching 43%.

Your S trim ''Rate of change'' is too aggressive. Also try to limit the s trim to -15 to +15% maximum correction. This might require getting the fuel map worked out a bit but it will be worth it... Always set your fuel map so that it requires minimum S trim correction.

 

I had the S trim set at 20/-20 but put them and all the temp correction values back to stock to see if that helped anything.

I'll drop s-trim limit to 15/-15. What is a good rate of change? It is set at 17, isn't that very slow?

I guess the big thing is what is causing the sudden lean condition when just before under basically the same conditions it wasn't lean.

I just tried a known good ecu. It didn't stumble, but it felt like it wanted to a couple times (again I couldn't get the car to stumble at all today). I'll try it again later tonight but I'm thinking this is not ECU related.

Thanks!


Edit-> On my cruise just now S trim was generally ranging from 6 to -6 with some dips to -10. It didn't seem to exceed 6-8 frequently on the positive side at steady throttle.

 

why are both of the high and low map breakpoints the same?

Usually in s300 I see 500rpm to 6000rpm then the high from 3krpm to redline.

I was also going to suggest a new wideband. If you have an aem amazon has the sensor for about 55 bucks.

 

Are you talking about the secondary timing/fuel tables? I never messed with them, just how the tune was set up from the day I started using S300 (tuner did it that way I guess).

I'm using the PLX M300. The controller is probable 10 years old. Could it be going bad?

 

Bye

 

Now that I think about it when we had it on the dyno the dyno WB and my WB were very similar.

I can see about getting it back on the dyno for just a bit to make sure the WB is working properly.

Tonight I'm going to go out and check the wiring going into the ECU. Doesn't cost anything and it's worth a shot.

Thanks for everyone's help. I'm going to drive it a lot over the weekend in hopes it will do it again.

 

Check the resistance on all the signal wires to the controller power and ground.
Good luck

 

Hey bro I sent you pm but thought if update you, I got everything working now. ran the cpr harness though the port where the ac port used to be.

Works pretty well so if you need help man just let me know but it's not that bad.

Now I just need my br fittings coil plate