Jason Trumpio

Here's the deal, my car has ASP Stage 3 fueling, and my co-worker's car has the same fueling as well, only difference being I have piggies and he has ASP downpipes.

Shortly after I got my car running I had noticed some annoying cold start issues, such as the car not banging over right away, and a lean popping when accelerating gently.

I had lemmitweaked +15% on warmup and that made the starting just like stock, banging over right away.

Normally when I cold start, I sit and let the high idle die down before I take off. But it seems these past few days the stumbling has been so bad I'm beginning to wonder what's going to happen in colder climates. My co-worker has been complaining as well, since the temps have dropped about 10 degrees in the morning recently. (high 50's)

I hooked up the wideband and verified my suspicion:

<img src="http://gallery.trumpio.com/albums/Misc01/coldstart.jpg">

It's completely cutting the fuel between 2-3k at part throttle when it stumbles (imagine pulling into traffic from a parallel spot driving like a normal human, it's not like I'm even approaching 0 vacuum or boost)

The only other tweak is -3 degrees of timing to keep my CF's around 8-9 on cyls 2 and 5 (91 octane sucks). Idle is around -22 inches of hg. and everything is stoich when warm.

Suggestions? Flaky IAT? Punch self in face for ruining daily driving characteristics?

ChucktownS4

swap'n the ecu maybe? did u scan with vagcom?

Jason Trumpio

No codes, and it happens on 2 different cars with the same software.

PSmalls::AnalRetentiveNumbNut

Mike Moore was telling me you're supposed to be richer than stoich on initial cold start, but I start ~15.5 and come down to stoich rather quickly. Is that wideband log from intial start-up? If not, what does it look like right when it starts? I'm starting to think you're actually supposed to be leaner than stoich on cold start to warm things up quicker, but I just don't really know...need to spend some time reading about this.

PSmalls::AnalRetentiveNumbNut

It's fine after it's warmed up, though?

ChucktownS4

sounds like a software glitch then

Captain Matt, I be

code just doesnt like 91 octane perhaps? who knows?

BLK01S4

then leans out.

sj6sp

Not saying that the reason isn't fuel related but misfires will shoot O2s sky high.

My car is a little stubborn when cold too. Same ASP code. I'm running bosch platins and was thinking of trying stock plugs to see if that helps.

Mike2kS4

It's common practice in every PCM I know of. It was used even back in the olden-days via the "choke" and later a "cold start injector". (Google those terms to learn more).

If you want some Audi-specific proof of this, think about what happens to fuel economy on an S4 when a coolant temp sensor goes bad (99.9% time reading cold since it goes from high to low voltage).