[Gmecm] Two '747 problems

[David Haggard]

BLM's are between 125 and 130 all across the board.

 

The fuel pump is a new in-tank unit for a 1990 TPI. Fuel filter is new.
No vacuum leaks anywhere I can find. I even replaced the intake gasket
to be sure. IAC shows no sign of sticking. There is no EGR, and the EGR
routines are disabled by setting their thresholds at extremely high
temps and speeds. (EGR is set to open at 254 mph.)

 

I'll look into any and all suggestions. What I've received so far has
been helpful in that it helps me think of different possibilities.

 

David

 

________________________________

From: nhromyak at comcast.net [mailto:nhromyak at comcast.net] 
Sent: Friday, March 11, 2005 3:53 PM
To: gmecm at diy-efi.org; gmecm at diy-efi.org
Cc: David Haggard
Subject: RE: [Gmecm] Two '747 problems

 

Stop and then restart and it is fine?!?!?  I am not familiar with the
747 tunning, do you have BLMs?  what are they like before and after the
stop and restart?

 

Could it be a lazy or plugged fuel pump/filter?

 

Maybe the IAC is leaking.... or stuck?!?!

 

EGR?

 

Heh, I don't know...

 

	-------------- Original message -------------- 
	
	> Thanks, Nick for the thoughts. 
	> 
	> My manifold is Holley, but my TBI is a factory unit from a '93
454 
	> Chevy. I also failed to mention that the injectors are
flow-matched 350 
	> Police injectors. 
	> 
	> The funniest part of my first issue is that after I stop the
engine and 
	> restart, the idle is perfect from then on. 
	> 
	> David 
	> 
	> > -----Original Message----- 
	> > From: NICHOLAS HROMYAK [mailto:nhromyak at comcast.net] 
	> > Sent: Thursday, March 10, 2005 9:36 PM 
	> > To: David Haggard; gmecm at diy-efi.org 
	> > Subject: Re: [Gmecm] Two '747 problems 
	> > 
	> > I have the same problem with my TBI based 402 BBC. I keep
thinking I 
	> have 
	> > an exhaust leak 
	> > But that should make it go more rich. When it is in open
loop and a 
	> > little 
	> > rich, I get a smooth idle. 
	> > perhaps we have a lazy O2 sensor, or perhaps a vacuum leak. 
	> > 
	> > After chasing it down for the longest time, I changed my O2
voltage 
	> > readings 
	> > at idle. I am not sure if this can be done in the 808, but I
think it 
	> can 
	> > be done in the 747, it certainly can be done with the 7730. 
	> > 
	> > I too have Holley TBI (4 barrel). To the best of my
knowledge these 
	> > aren't 
	> > leaking, I have had them for six years now. 
	> > 
	> > Good luck. 
	> > Nick in Sacramento. 
	> > 
	> > ----- Original Message ----- 
	> > From: "David Haggard" 
	> > To: 
	> > Sent: Thursday, March 10, 2005 5:04 PM 
	> > Subject: [Gmecm] Two '747 problems 
	> > 
	> > 
	> > I have two tuning problems I can't seem to figure out. The
ECM is a 
	> > '747, '88 305, moderately cammed, 454 TBI and Holley
Pro-jection 
	> intake. 
	> > 
	> > 1. After cold startup, the idle will never settle down to a
smooth 
	> idle, 
	> > even after driving and fully warmed up. The idle oscillates
between 
	> the 
	> > target setting and about 1800 rpm. The throttle follower
seems 
	> > overactive. But once the engine is warmed up above the
closed loop 
	> > threshold, if I shut the engine off, wait ten seconds, then
restart 
	> it, 
	> > I get a smooth idle at the target setting, and the throttle
follower 
	> > acts perfectly. 
	> > 
	> > 2. I have a bad flat spot under gentle acceleration, between
1600 and 
	> > 1800 rpm. I experimented with lowering the PE TPS threshold
to 20%, 
	> and 
	> > the flat spot is gone if I open the throttle past the 20%
point and PE 
	> > is enabled. The flat spot is there under any acceleration
below the PE 
	> > TPS level. The main fuel table has been tuned to give BLM's
of about 
	> 126 
	> > in that RPM and throttle range, using WinALDL. The spark
table has a 
	> > smooth, straight-line advance curve through that RPM range. 
	> > 
	> > Any ideas would be greatly appreciated. 
	> > 
	> > David Haggard 
	> > '88 Formula Firebird "SR-71 Black 'Bird" 
	> > 
	> > _______________________________________________ 
	> > Gmecm mailing list 
	> > Gmecm at diy-efi.org 
	> > http://lists.diy-efi.org/mailman/listinfo/gmecm 
	> > 
	> > 
	> 
	> 
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