Troubleshooting lean issues under opening throttle

Hi, I’m currently mapping my first car following the 10 step process and have hit an issue. I have got the car idling fine and with a decent AFR at Circa 1500rpm and have used the formula to build a base map for the rest of the range. However whenever I operate the throttle be it slightly or if I punch it the lambda reading just goes lean and the revs drop and it tries to die. I can just about drive it/build revs if I’m very very gentle with the throttle. I’ve tried all the different variations of the throttle enrichment setting but it feels like it makes little to no difference at all, and I can’t move on any further until I have it in a more drivable state.

I’ve checked all the sensors are reporting as they should, replaced the vac lines, replaced the wideband, gapped and replaced the plugs, swapped out the adjustable FPR for a stock 3 bar one (as I know you can’t always trust the gauge that comes with them) to rule it out but nothings made any impact. I’m thinking I might have a more fundamental issue I’m over looking and wondered if you could maybe give me your thoughts and some other things to try/test. I’ve attached a video of the issue so you can see the behaviour. (Ignore the misfire one of the coils played up as I took the video.

Spec is:

VW golf vr6 turbo, kms mp25 standalone, Bosch 550cc injectors (deadtime was a pain to find but I believe is correct could this be an issue perhaps?).

Any advice gratefully received. Thanks Ed.

First, why is your fuel correction still 11-12%? I thought it might be because it wasn't warm, but the ECT is 84c. Perhaps you whole table needs to go up 10-12 % in the idle area, and remove whatever correction is being applied.

Regardless, of that I would try adding fuel to your 1000 RPM / map 1-2 cells. Probably make them the same as your 750 RPM row.

Next, your ignition timing should probably be advanced (particularly if you don't want to add the fuel) in the 1000 RPM / map 1-2 cells. I bet 2-4 degrees will make a difference.

The area you are working on is called "tip in". This is where you leave the idle and start to raise the RPMs. You might want to make sure the idle control will see the TPS change is enough to exit idle control, since the idle control could try to reduce the engine speed to hit the target idle.

Hi David, Thanks so much for the reply. The only corrections being applied should be the start-up parameters and the air temp. Altohugh i've noticed a small mistake on there now you mention it so I'll correct that for starters.

I'm happy to add some fuel into the table but to be honest if when I'm at normal operating temperature I add much more in it tends to run 0.85 lambda and below and I just didn't want to be that far away and start fouling the plugs (again).

I think the idle control settings should be fine but I'll definitely try adding some timing in and seeing if it makes a difference and let you know how i get on. I seem to remember one of the tutorials talking about tip in, I'll see if I can find it and give myself a refresher.

FYI I've attached a screenshot of the timing which i got from your reference material. The tables not the clearest I know but 0-15 across the top is 400kpa evenly split so circa 25kpa per cell. Obviously 8000+ is not in use and I didn't want to use those cells and make it any bigger than it already is.

Thanks again for the help! Ed

As David said, add the fuelling and removing the correction(s) would be a wise move.

As also suggested, there may not be quite the resolution at off-idle - it's normal practice to have the low rpm/opening/load positions closer together than the high rpm/opening/load/flow, etc, as the percentage increments are more important there. On that, double check to see if the ECU is picking up the change from idle from it's sensors/senders.

Thanks Gord. If adding timing/fuel does get it done I can look at disabling the idle control to rule it out too. Also noted what you've said about increments. Unfortunately I can only add increments in RPM as the MAP readings are static depending on the map sensor. The only way I could affect those would be replace the 400kpa one with a lower value one I guess.

Extra post-start fuel corrections should not last more than a few seconds at normal operating temps (might be a 10-15 seconds if really cold). Coolant temp compensations should really handle the most of the needed enrichment. Do you have an overall-trim somewhere, or is closed loop control adding fuel?

I agree with Gord's comment about MAP axis resolution (axis breakpoints) -- you should have about 10kpA steps from 30 - 60 kPA, as the efficiency can change quite a lot there.

OK, knowing that the map steps are 25 kPA, there is no way that the fuel at 1000 RPM Map1 and 1000 RPM/Map2 should be the same. It's going to have nearly twice the air, so you would expect the pulse width to be much higher. Try adding 10-20% fuel to the Map2 750 and 1000 RPM cells. When you open the throttle those are the next cells that are going to be used -- they need to have the proper fuel.

Thanks for the info. RE: the compensations. I believe the correction's you're seeing are the compensations just being shown there. It should apply water temp +5% @ -20degrees to 0% @ 60degrees in equal increments, and for the air temp +10%@ -20degrees, 0% @ 20 degrees and -10% at 60degrees and so on (although as I mentioned there was a mistake around 60degrees adding 10% rather than removing it)

No overall trim that I'm aware of and closed loop is currently disabled.

I'll work on the fuelling like you suggested and drop a couple of degrees timing in and see what effect that has. I do have cell interpolation on so I guess at the current resolution I'm stuck with I'll be relying on that to fill in the gaps.

Hey guys.so I went up to the car earlier and applied what you had suggested and it worked like a charm! Thanks so much for your advice! I was able to quickly dial in a smooth response with some extra fuel and about 5-6 degrees of timing. Really appreciate the fast response. I can finally move on to some steady state tuning, only wish I asked earlier rather than struggling for a couple of weeks!

You should make another video showing table changes and how it responds. I know I would like to see it!

Hi, sure thing, it’s not a very exciting video I’m afraid and the changes were pretty crude and restricted to the area around idle as I only had a short time to pop up there after work, but I wanted to prove the theory. You can hopefully see/hear the difference where I can touch the throttle without it trying to stall or showing fully lean, and I feel like I have some thing better to work from now.

The idle is definitely a little on the high side due to the increased timing but I can worry about dialing that in next time.

EDIT: Ignore some of the corrections shown on the video I had forgot I turned closed loop a few minutes earlier to see how it behaved.