89' Stang - MS2PNP - Post tune - Surging issues


New Member
Jul 6, 2013
Hello I'm new to this forum, new to tuning megasquirt. A guy mentioned on facebook for me to make a post here with a datalog and tune file

This car, with this setup ran with the A9L fairly well, and I have a vacuum gauge in the interior, the cars vacuum levels dont appear to have changed since it was running with the A9L

1989 Mustang
MS2PNP wired with AEM 30-5130 Wideband to pin 21 and 22 on options port on ECU, and factory O2 sensor harness is unplugged from the main harness on LF apron. Wideband is grounded to engine on LF cylinder head along with the factory injector harness ground. Sensor is mounted approximately 24" back from the collector, BBK longtubes with a V-band style clamp to exhaust.

333ci stroker (3.25" Stroke, 4.040" Bore)
Performance World PRO185 heads (these are a chinese recast of AFR 185's)
GT40 Explorer intake, upper ported for 70mm BBK Throttlebody, Lower port matched to the heads, and the bends in the ports radiused
Comp Cams XE270HR camshaft
Ford Racing 47lb injectors
Walboro 190lph pump
BBK 1-5/8" Primary Longtubes

The car was taken 900km from home to Tecmotion in Calgary for a tune, there we had immediate issues with the Innovative LC2 installed at the time. The LC2 wouldn't match his Dyno Wideband, and on the dyno running the car off the LC2 made it run very poorly. So the tuner decided to tune it in closed loop, the car ran great and made 280hp and 313ftlbs of torque. It did have a small bit of a surge on the dyno at times but it would clear up. He assured me that I could drive the car as is and to just change the LC2 out for something that works when I had time.

Got the car home a few days later and upon starting the car it surged so bad it was difficult to drive it off the trailer, I again passed it off as the engine being cold.

I then tried driving it which found even after the car has warmed up the surge doesn't go away, sometimes it gets worse. Typically its about a 900-1200rpm surge, sometimes worse.

I've been on and off the phone with him regarding it, he guided me through a few things to help. He said to adjust mechanical screw slightly, then resetting the tps. Lower the PWM values at idle. and lower closed loop-gain. This made the idle to settle to a 850-950rpm swing which I was okay with, although touching the throttle would cause it to surge as the RPM's dropped back down to idle sometimes continuing for 5-10 seconds after. The following day I drove it to work, and the surge while driving was way worse then before, and it stalls now, and sometimes doesnt want to restart again. And even sometimes it sounds as if it is backfiring through the intake.

After that day I made a post on the Megasquirt facebook page and I was told to make a post here with a tune and datalog attached, as well as get a wideband in the car. So I've returned the LC2 and got a AEM 30-5130. The datalog should show the wideband now.

The tune and datalog is in the condition i got the car directly from tecmotion, I returned the idle screw to the same location and reflashed the ECU with the original tune with the only change, adding the wideband.

Hopefully someone can help me out, guide me through in a sort of step by step fashion.

Thanks in advance



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Mod Dude
Apr 6, 2011
Hillsborough county
This is not a review of techmotion as I do not know them or who does there tuning, this is simply stating what I see in the datalog and the tune file.

-The first mistake I see is not incorporating AFR into the fuel equation, its too late now that the car has been on the dyno. This can of course be fixed but an entire remap of the fuel table may be required. It looks to be a WOT tune so not that big a deal.
-I see nothing done with the MAT correction but this may not be needed if the IAT has been moved out of the lower intake. If it is still in the lower intake then I can fix the air density curve for you.
-They did not bother even trying to setup ego correction, takes all of 3 minutes to do.
-dead times are not correct, I assume these are the LU47 injectors from ford racing. again this will alter the fueling.
-if the car was on the dyno for tuning, they did not spend any time working on the IGN table. its basically the can tune table, it does look like the ign values may have been optimized for 93 octane but the curve is basically the stock ecu with 4* advance at wot.

This is my review, you may want to reach out to the shop or tuner and ask them to fix it. If it was idling well before you left they may not even know you are having this issue. The above are based solely on my opinion only and do not reflect on the shop as a whole.

IF you would like I can help you fix it.


Mod Dude
Apr 6, 2011
Hillsborough county
download anydesk, and then pm me on FB. we can set a time up today to get you fixed up. I have to run some errands but I can make time a bit later today.
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