Does this sound like a tune or DI failure problem?
 

I have an automatic. When I brake after the car is warmed up (RPM never drops when engine is cold), my RPM's drop down to about 450 and my car shakes and I hear a rattling. This also happens every time I shift from Neutral to Park, or Park/Neutral to Drive. It ONLY happens when I brake or shift to drive.



I never had this problem while on OFT but when tuned on Ecutek, this started happening. I'm also getting P117B/P1170 codes, both pertaining to the DI and PI. There is no way that these two systems failed at the same time so I'm leaning towards the tune, but what do you guys think?


I suspect something with the MAF scaling, but I'm not a tuner so I wouldn't know.

Did this happen straight after the tune?

Was it a canned tune?

Custom tune from a reputable tuner and yes, happened after the tune.

Take the car back to the tuner, he will be able to diagnose the issue.

Don't work behind your tuner's back. If you think of them as reputable, let them earn this praise by fixing the issue they accidentally introduced :)

I understand that DI only works during certain engine load/RPM, right?

If my fuel trims are maxed during idling while my car is warming up, then why aren’t they high when idling AFTER my car is warmed up?

I really can’t figure out if it’s a tuning issue or DI issue! I doubt it’s a vacuum leak as well because of the fuel trim differences from cold to warm.




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Cold start use at first 100% PI, then 50% PI
Then when it s warmed it uses the PI/DI ratio tables, most often it s 100% DI during idle

That s pretty hard coded into ecu

Does this sound like a tune or DI failure problem?
 

Well that’s very weird then. I don’t know what to believe anymore. Tuner is pointing to DI’s, but fuel trims are normal when idling. Only during cold starts is where fuel trims are funky!!! Warmed up, the car is good.

Maybe it’s a problem somewhere else.. i haven’t gotten under the car to check for exhaust leaks yet.

Also, when you say it’s hard-coded in the ECU, do you mean that there is no way a tuner can edit those ratios?

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yes, you won't change that behaviour
you can see it if you log real time

maybe you could try a cold start with normal petrol instead of e85 and see what happens?

Hey guys. I just got a second opinion from another reputable tuner on the platform and he said that my issues are within the tune and that he sees both my DI and PI's working fine, just that the scaling is off with the MAF and whatnot.



How do I approach my current tuner with this information without sounding like an asshole?

Reputable tuners?

Two different opinions?

@haute I have read about this issue a few times on this forum, automatics partially stalling on braking to a stop.

On my MT car I had an ABS code once and the car was sent into limp mode, it would also try to partially stall like that on braking, even if I had the clutch in. Guessing here, maybe AT models go into a partial limp mode when you have a P-Code affecting your open/closed fueling maps, make the car drive like crap until you fix whatever the issue is. Maybe the ECU telling you it doesn't like something from the ecutek tune and throwing the code? Have you tried going back to the openflash tune?

Thank you. That might be it because once I clear the code, the car magically brakes fine again. I have not gone back to OFT since I sold the tablet.