[Gmecm] Two '747 problems

[nhromyak at comcast.net]

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" 
> > 
> > _______________________________________________ 
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> > Gmecm at diy-efi.org 
> > http://lists.diy-efi.org/mailman/listinfo/gmecm 
> > 
> > 
> 
> 
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