Idling issues after driving and flash of ecu

[N3RDPWR]

First of all, I've gone through and done some MAF Calibration... its still out, but no where near out as it used to be.

Each time I flash my ECU the idle control is rubbish and it will take about 150km before it comes good and stops stalling.

I've done a few logs of this happening where I'd be driving at a cruise speed at say 100km/h.
I will back off (still in gear) due to traffic or traffic lights. And I would normally expect the Lambda to go straight to almost a value of 2. However it does quite the opposite. It goes down to ~0.630 and then it might go back up to ~2 if I'm off the throttle long enough.

After coasting for a while (still in gear) I take it out of gear and then the car will drop down past the idle position and fuel up again to the point where it stalls...

I've got a log of this happening, I can post it up if that helps... (just need to get it off the laptop)

Anyone got any ideas how to fix this?

[mituc]

When you lift your foot off of the throttle the lambda should go to about 2, no matter how rubbish your mafcal is (when engine braking the maf cal doesn't even matter).
I suspect it's something with the injectors themselves, or, the best case scenario just the seals. Apparently after you lift your foot off the throttle somehow you're still getting gas sprayed or leaking into the cylinders which eventually reaches the exhaust (so the lambda sensor there as well).

You may also need to check your lambda sensor (the first one on the top of the downpipe).

And you say you don't get this behaviour with the stock or previous tune?

[N3RDPWR]

I hope I'm not speaking too soon..

I think I may have fixed the issue, but need probably another day of driving it to be sure.

Each time I flash the ECU the fuel trims reset themself back to 0% and re-learn the trims based on temperature, baro pressures, etc
The car run "ok" and idles ok after driving it. Leave it to cool down over night and then it starts to drive like a bag of shit and starts to drop the idle and stall.

Being a problem solver myself I couldn't help but look around at every single option there is.
After looking around with no avail, It came to me while driving along... The idea....

My car was running so rich that the MAF Calibration was modified big time... (in some instances I took out up to 40% of MAF g/s)

So after adjusting the MAF settings all should have been ok... but this wasn't the case... my results were skewed so much that the LTFT Partitions were out of skew now.

So they were Set to default:
0-5.7
5.7-18
18-30
30-200
200-200
200-200


I found that some of the crusing was happening in the first partition in low gears low load... and fueling up maybe a little too much when the trim had adjusted.

So I thought, why not... It can't hurt to change them...
I Looked at the original values of the MAF and set the partition values based on the previous voltages that were associated with the original Partition values... Sound confusing?!?!

On a Stock tune 5.704 g/s is at 1.482 volts
On my tune 5.704g/s is closer to 1.7 volts

If I take the value closest to the 1.482 volts in my tune its more like 3.73g/s

So I used this concept and translated the volts to the partitions and now I've modified my LTFT Partitions to the following:

0-3.3
3.3-12
12-20.5
20.5-40
40-200
200-200

(I added the extra one in for good measure.... and probably could add another just because its there and why not use it?)

So this ends my story and time to move on to more calibration... but I hope this could help someone else out that might be having the same problems as me... or you could think I'm crazy for changing the partitions? but I think the Partitions should be a crucial part of the MAF Calibration 101?

[Steve @ VersaTune]

It sounds like you've actually gone to a smaller MAF than stock. That is quite unusual. Keep an eye on MAF volts at WOT. The ECU will try to reduce load as you approach 4.9v.

I will add a section to the MAF Cal 101 about LTFT partitions.

[keridil]

Maybe I'm doing the next question 'cos my ignorance, but did you clean your MAF?

[mituc]

What Keridil says, clean your MAF and eventually the throttle body.
I have a Cobb SRI so the MAF housing is not too much larger than stock, and at 1.7V I'm flowing close to 10g/s. What intake do you have, btw? Maybe some forum member with the same intake can share his MAF cal with you.

Later edit: just saw what intake you're actually using: Custom Injen SRI (Chopped). ?!

[N3RDPWR]

To answer some of your questions...
Yes, I cleaned the MAF as per the MAF 101. I gave it a few good blasts with cleaner. It didn't really make too much difference... but it did look cleaner


http://www.streetunit.com/ProductDetail ... ode=SP6062
I orignally had this CAI... however it was in the way when I put in the FMIC. so we mad the decision to chop it into a SRI

[mituc]

Well, the inner diameter doesn't seem to vary, so I guess the chopping didn't really affect anything air flow wise.

What are your fuel trims at idle and say, when you rev constantly to 1000rpm (or 1500) while staying parked? Take a log with that and post it here.
Also, take a log as per the MAF cal user guide but in the parameters list also add MAF g/s, and post the log here (the log at 1000-1500rpm should have the same parameters logged).

[Steve @ VersaTune]

I would be surprised that any "bolt-on" type intake would be that far off from stock. Either there is a leak somewhere or there is a major pipe bend or source of turbulance before your MAF.

[N3RDPWR]

Ok,

I've attached the log and done the requested for idle and holding at ~1500 rpm... NOTE: I've upped my idle to 900 rpm due to the lose forged pistons making lots of rattling noise when idling too low

Also picturtes of the engine bay

Ok, well I tried to upload the attachements....
Could not upload attachment to ./files/339_a30fa162d1e3421cb2c3f43e4e16544f.