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**doc_rock** · 04-29-2022

So, this was my first trip here: http://www.gearhead-efi.com/Fuel-Inj...light=doc_rock
84Elky helped a tremendous amount and really got me aimed in the right direction, but over the course of the last two years I've identified and fixed more issues, and made quite a few realizations (I think). One of the big ones I found was a temp sender that was failing to ground at temps over 90c, which was grounding out the 5v reference circuit...
So now that I've got it down to a fairly close tune - I'm looking for help on figuring out low RPM bucking and backfiring.
Initially I was using the S-AUJP bin, but I've come to the realization that the manual and automatic are two totally different tunings - and I don't know that I have been able to copy off the differences correctly between the two - seems easier to start with a manual .bin and go from there.
So, what we're dealing with here:
This is a 1990 F car, 7730 ECM with a T-56 and a 4th gen G80 rear end (3.23 gears)
The closest stock configuration I can find to what's in the car is the AXCN .bin file from a 1991 Corvette.
I have copied and am using that bin directly in the 7730ECM - the only changes I've made to it are adjusting the VSS settings to get it to read correctly on the speedometer, and correctly in the ECM.
I did have a dakota digital box, but I could never get it to stop fluttering in neutral, sitting still - (this is how I realized that contrary to a lot of things I've read, the speed sensor is extremely critical to the ECM)

What I'm fighting with now is low RPM/high load (like accelerating out of idle speed in gear) backfire, bucking, and in general miserable behavior, and part-throttle backfire during acceleration. Essentially if you drive it like a total jackass it performs perfect. If you drive it just above granny-level it performs perfect. It you drive it like normal people, it is absolutely miserable.
This is totally conceptual discussion, questions and answers, and may take a while (I don't have much time, I'm trying to deliver this to my aunt by the end of next week - and it's probably running good enough for that) but - where do I start?

**ralmo94** · 05-01-2022

Plugs wires rotor all on good shape? What does she AFR or O2 sensor do when it happens, what is the timing doing when it happens?
Have you tried reviewing a data log with the EKG type lines to look for a poor TPS signal, map signal ECT?
That's all "I" can think of. Sure someone else will chime in.

**doc_rock** · 05-04-2022

Originally Posted by ralmo94

Plugs wires rotor all on good shape? What does she AFR or O2 sensor do when it happens, what is the timing doing when it happens?
Have you tried reviewing a data log with the EKG type lines to look for a poor TPS signal, map signal ECT?
That's all "I" can think of. Sure someone else will chime in.

New cap, rotor, wires, and plugs. New TPS which has smoothed the trend line on its operation. New IAC since the old one was sticking open about 15 steps. Now (since this posting) I have developed an issue where it will only datalog for a short time then stop all communication with the serial module. I am guessing it is a grounding issue, but I can't seem to pinpoint that just yet.

**ralmo94** · 05-04-2022

Originally Posted by doc_rock

New cap, rotor, wires, and plugs. New TPS which has smoothed the trend line on its operation. New IAC since the old one was sticking open about 15 steps. Now (since this posting) I have developed an issue where it will only datalog for a short time then stop all communication with the serial module. I am guessing it is a grounding issue, but I can't seem to pinpoint that just yet.

Where are your sensor grounds? If they are on the thermostat housing, consider moving to the block or head.
That's all I got.

**doc_rock** · 05-05-2022

Originally Posted by ralmo94

Where are your sensor grounds? If they are on the thermostat housing, consider moving to the block or head.
That's all I got.

I've got grounds everywhere - the thermostat housing is a remote setup, so i tapped into that and ran a ground from that to the block. ECM grounds are at the back of the driver's side head where they were originally. body to block ground is back of the passenger side head, where it was originally - and another ground ran from body to battery.
The datalog is driving me nuts. I'm not sure if it's something with the serial to USB connector, the ECM, or the laptop. I can't reliably reproduce it, and there doesn't seem to be any method to it. Sometimes it logs for a few minutes, sometimes only for a few seconds. ALDL connectors all pin out with 5v, ground to ground connection is solid.

**ralmo94** · 05-06-2022

Originally Posted by doc_rock

I've got grounds everywhere - the thermostat housing is a remote setup, so i tapped into that and ran a ground from that to the block. ECM grounds are at the back of the driver's side head where they were originally. body to block ground is back of the passenger side head, where it was originally - and another ground ran from body to battery.
The datalog is driving me nuts. I'm not sure if it's something with the serial to USB connector, the ECM, or the laptop. I can't reliably reproduce it, and there doesn't seem to be any method to it. Sometimes it logs for a few minutes, sometimes only for a few seconds. ALDL connectors all pin out with 5v, ground to ground connection is solid.

Stupid question, not using an inverter are you?