1228746 TBI 305V8 stumble

[WEG1192 at aol.com]

In a message dated 9/28/2001 4:58:14 PM Eastern Daylight Time, 
jwvess00 at home.com writes:

> Small-cap HEI from the donor had a cracked module connector and did not
>  look to be in that great of shape.  In an effort to keep the new
>  cap/rotor/coil/plug wires that were on the target car, we just re-used the
>  original large-cap distributor.  I removed the small-cap 4-wire module plug
>  from the TBI harness and spliced in the 4-wire module plug from the CCC
>  harness original to the target car.  No codes set.  Timing is adjustable
>  with the bypass wire disconnected.  Timing goes to about 12 degrees (from a
>  base of 0) with bypass plugged in so I believe the advance circuitry is
>  right.  

Does the CCC distributor have a vacuum can on it? If so, you may have the 
retard only distributor. Im not that familiar with those year cars but you 
may not be getting any timing from the ECM, only the retard signal. This is 
just a thought. If you are using an 8746, you need the correct ignition 
module so that the ECM can control timing. Look at www.customefis.com in the 
DIY section and you'll see how to make any HEI distributor a computer 
controlled unit.

If the TBI return line was blocked, your fuel pressure would go sky high and 
cause the engine to run rich. You can test this by pinching the return line 
and see if it causes black smoke at idle. It may even clear up the problem if 
you partially pinch the line while trying to get it to stumble off idle. If 
so, then you know you are running lean.

If you have access to an EPROM programmer and eraser, you can try my AFRTOOL 
trick to see where the engine is running lean or rich. You don't need a 
scantool with this trick. The only thing a scantool gives you that any other 
instrument can't is access to the BLM and integrator numbers. If you are in 
open loop, they aren;t needed to see where you are rich or lean.

By the way, you don;t need a potentiometer to try this trick. Just program 
the open loop vs. coolant table in the normal operating range of say 150- 220 
degrees F with the AFR that you want to test. Then drive the car until it 
warms up. If you program a 10% leaner than 14.7 AFR at 190 F and it still 
runs rich at a certain MAP and RPM intersection, the VE value at that 
location is rich by at least 10%. For more details on how to do this, check 
out www.customefis.com/afrtool.html .
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