jared1264

Hello!
​​​​​Been working on my first third gen for 2 years now and been trying to learn the tuning part for the last year. 89 RS convertible but someone before me put a 350 block with 305 heads in. Drives good but timing and fueling needs adjustment. I'll run down my issue and let you know the new parts over the last 2 years.
While driving, sudden increase in throttle will backfire out intake, multiple times if I hold the throttle after the first one. Never backfires from take off though. Happens while driving. (10-40mph) more common when engine is hot. I suddenly apply throttle, (more than 50%) it hesitates, backfires, and I release the throttle.
Checked timing, it was +6 but ECM base was 0. I adjusted both to get it more nominal. Mechanical to 2.5 advance and set the ECM base timing the same. The backfires became more often and even backfired gassing out of a turn. So less advance made it worse. I then went to the main spark table and advanced the whole table 2 degrees. Got better. Then advanced another 2 degrees for a total of 4 degrees from ANLU starting point. Now, it' not easy to make it backfire, but i still can.
It throws a code 43 and also a flag. "ESC 43b Ready for second PE" ( Don't know what that means).
System runs rich right now. BLMs mostly float in the high teens and 20's.
I replaced:
ANLU bin
Knock sensor (for 350)
ESC module (for 350)
Coil
Plugs
Entire distributor and wires
TPS ( set to .57v)(within threshold)
TBI rebuilt
15 PSI fuel
Injectors for 5.7 caprice (spray good)
Cylinders passed compression test.
EGR valve
Removed and cleaned intake manifold.
Premium gas (someone on another thread suggested premium because of 305 heads on the 350 bumping the compression.
​​​
From what I've read, intake backfire is usually a lean condition but all across the BLM chart says I need to remove fuel.
Is it a timing issue then?
Any suggestions or questions about what I'm doing that could cause this?

Any help is greatly appreciated.

jared1264

Photo of my log. You'll see where I punch the throttle and then release because of the backfire.

RBob

iTrader: (1)

Backfire out the intake is either lean or not enough spark advance (or both). There is also AE to be considered

RBob.

jared1264

Thanks RBob!
So It's been awhile but I ended up really pumping up the AE fueling numbers to eventually get rid of the backfire. Played with fueling table as well to improve the BLM counts. Still was throwing the 43 code. Another thanks the RBob and his replies in other threads because it was failing the knock test so I bumped timing about 3 degrees across the board and no code 43 now!
So I must have needed more timing, so I added another 2 degrees and gained some more torque on take off. I keep advancing and like the results. My question is, when do I stop? Any parts of the SA table I should avoid messing with?