Surging while driving, at touch of throttle

[webb1624]

Car cranks and idles good. Drives good and runs great. This issue I'm having is when I'm driving and I barely open the throttle It starts surging. This happens at low speed and at cruise speed. I'm talking like 1% tps opening. If I go passed say 3% tps it goes away. The attachment shows it happening about half way through.

Car is a 1988 Ford Mustang
1998 Ford Explorer block 347 ci AFR 185 heads
Holley Systemax II intake
Buddy Rawls cam
Mac 1 3/4 shorty headers
2 1/2 inch exhaust
75 mm TB
42 lb/hr Bosch injectors
Walbro 255 lph pump
Ford Explorer ign coils
MS3 w/ MS3X expansion V3.57
LC 2 wideband (2)
4R70W with Baumann Opti-Shift controller
Precision Industries lock-up convertor 2800-3000 stall
1996 8.8 rearend with 3.73 gears, disc brakes
Cobra 13 inch disc brakes
Eibach springs, Koni shocks and struts

[whittlebeast]

Flatten your VEs in the idle area and flatten you timing in that area. Add fuel in that area until you get about 14 AFR and post the results.

[webb1624]

My car will not idle any lower than 17 - 18 AFR. If I try to richen it up it surges really bad at idle. I have messed with the fuel and ignition maps a lot to try and get the AFR's down to 13 or 14 at idle and my car doesn't like it at all.

[whittlebeast]

Something is messed up with your wideband. Calibration in the squirt is the first thing to check.

Andy

[webb1624]

I have calibrated it several times and even installed 2 new O2 sensors. I have 1 in each exhaust

[39ClevoUte]

Hi VE Fuel tables seem very course. You may be cruising at a low setting and as you touch the throttle its jumping to the next cell (big jump)
Also I would get rid of the high kpa settings in the AFR table and spread your numbers out a bit more.
You also have large jumps in your spark advance table, this can also surge. I use 8 deg on idle to make my engine idle smooth, as soon as RPM reach 900 it jumps to 14 deg the surge is very noticeable.
regards Rob

[DaveEFI]

I have calibrated it several times and even installed 2 new O2 sensors. I have 1 in each exhaust

Look at your log, AFR is going very weak. Normal maximum at cruise would be something like 16:1 - as per your target AFR table.

Assuming your wideband is correctly calibrated, VEAL should sort all that out easily.

[39ClevoUte]

Hi I don't understand 100% accel enrichment at this stage, but you have it set to end at 1600 rpm and looking at your log its around here that the fuel drops and everything seem to go pear shape. Would be interested to know if doing something with this makes a difference.
Regards Rob

[webb1624]

I opened up the IAC a little and it made a lot of difference. It doesn't surge when tipping into the throttle anymore. It still surges once or twice with the A/C on when letting out of the throttle at cruising speed but that is a big improvement over the way it was acting. I'm still working on it to see if I can get it better.