[Gmecm] TBI and EFE

[Jared Ryan]

I just did a little reading on carburetor icing - perhaps it is happening 
a little bit, even though the ambient air is above freezing.  Hmmm.

I notice that it starts instantly cold and runs pretty well overall.  It's 
just a rough idle when it has warmed up that is bothering me.

On Fri, 1 Dec 2006, Rick McLeod wrote:

> J, even on my TPI's that are a 'dry' manifold, there is a TB pre-heat w/ a water passage bypass from the cooling system, I disconnect it in summer, but it makes a big difference in city drivability if not connected in winter!

I'd recommend having it, maybe you remember the old VW's w/ the carb preheat tubes from the past, they had a weighted flap that could be 'locked' open in summer, but the owners manual recommended not doing that 9 months out of the year, yes the cold/cool ones, I've seen ICE form on the carby in them!

Humid cool cliamate, like Houston when temp dips, I'll bet you're icing up a little, doesn't take much!


----- Original Message ----
From: Jared Ryan <jryan at caminofx.org>
To: gmecm at diy-efi.org
Sent: Friday, December 1, 2006 12:28:24 PM
Subject: [Gmecm] TBI and EFE


Do TBI engines typically need the EFE ThermAC setup to run smoothly in 
cold weather?

I have an El Camino that has a heat stove on the passenger side, but I 
recently changed to a Camaro air cleaner that puts the snorkel on the 
driver side (this fits MUCH better with my Camaro serpentine belt setup). 
I will need to put a heat stove on the left-side exhaust manifold in order 
to use the ThermAC.

I assume it wouldn't be there (on '88-'92 TBI F-bodies) if it didn't help. 
It made a BIG difference in cold-weather running when I had the QuadraJet 
carburetor, and TBI is also a wet-manifold system.

The reason I ask is that the temperature has dropped into the 30s F, which 
is cold for Houston, TX, and the idle is a little rough.  However, the 
cold weather moved in on the same day I removed and cleaned the IAC valve. 
It is entirely possible I just need to reset the minimum-air setting and 
the idle will smooth out.

Off-idle performance has been perfect, just a little bit of a rough idle 
since it turned cold.  I will do the IAC reset this afternoon, but I still 
wonder if making the ThermAC operational will help a lot.

I notice that the TBI intake manifolds no longer have the exhaust 
crossover under the carburetor/throttle body mounting pad.

I hear a lot about ThermAC, like "It only closes in *really* cold weather. 
When I had it set up properly with the QuadraJet, it would close at least 
a little bit on sunny warm spring days!  It would open quickly, but it 
didn't only work on very cold days, for sure.  On very cold days, like 
what we have here, it often wouldn't ever open completely.
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