[Gmecm] 7747 stumbling acceleration when cold

[Jay Vessels]

Hi there!

My first guess is that it sounds lean when cold.  Either the tune is 
off, or you've got a fuel delivery problem (i.e. clogged injectors, weak 
fuel pump, restriction in the plumbing).

I'd be interested to see the BLMs, wondering if they're high.  If it's a 
stock(ish) application then it's more likely a hardware issue than a 
tune issue.  If it's a transplant, and you're sure the hardware is 
behaving (and running okay when hot isn't necessarily an indication that 
the hardware is healthy) then some datalogging can really help point 
things in the right direction.

Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
2006 Pontiac Solstice

On 11/28/2010 02:31 AM, Bill Hamilton wrote:
> Could be several things but is this a stock system or did you swap it
> onto another engine?
> Have you logged any data?
> Is it only in open loop?
> My closed loop starts pretty quick.
> Did it just start happening and used to run fine?
>
> This must be a common problem as I have seen this same question a couple
> times this week on other boards.
>
> ------------------------------------------------------------------------
> Date: Sat, 27 Nov 2010 22:09:33 -0700
> From: charles at taildragger.info
> To: gmecm at diy-efi.org
> Subject: [Gmecm] 7747 stumbling acceleration when cold
>
> I'm hoping someone can point me in the right direction of what to change
> in my BIN to solve a bad cold acceleration issue with a 7747 TBI. The
> truck runs great once warmed up, but when the engine is still warming up
> (and worse on colder days) it stumbles through it's acceleration,
> sometimes even backfiring. It sort of comes off the line decently, then
> bogs down and gradually works its way up to speed. Any pointers on what
> I might change to fix this?
>
> Not sure if it matters, but this vehicle has an open air cleaner and no
> heat riser stuff. I don't think that should be the issue since this
> happens even when it's 55 degrees out, but I thought I'd mention it in
> case. Thanks.