Mustang wierdness

I’m trying out a new tune on my Mustang. Supposedly it enhances drivability (smoother idle, less popping when you let off the gas at high RPM, etc.) Additionally this new revision also allows the traction control to be used again. In previous versions the TC was disabled at all times. Anyway I uploaded the tune and indeed the engine is idling smoother and it runs smoother at lower revs. However there seems to be a glitch. Twice now the ABS light on the dash has come on for about 2 minutes then mysteriously gone off. The first time it happened I definitely smelled something electrical burning. The 2nd time there was no smell.

I have not noticed any difference in the way the car runs, the ABS still work as well. Previously the only time I’ve seen the ABS light come on was whilst performed a lengthy burnout (on private property of course) When that happened I just guessed it was because either the rear brakes overheated or the ABS computer got confused since the back tires were spinning but the front ones were not. In that instance the ABS light went off after a few minutes, and it never came on again until recently.

Coincidently on the two most recent occurrences the A/C was on.

Any ideas?

Perhaps you have a damaged wheel speed sensor?

And what is this “new tune”?

Um…and you do realize that you’re beating the livin’ stuff out of your car…you do know that people who do this accept that they’ll break things regularly. Visit a dragstrip sometime if you doubt my statement.

I do go to the dragstrip about once a month. The thing is the lengthy burnout I referred to was 3 years ago. This problem just showed up recently, last week more specifically. My car is built to handle this sort of thing anyway. I have a built 8.8 inch w/31 spine chome moly axles, girdle, Cobra-spec LSD, etc, and an uprated TKO 3650 tranny, That combo is good for at least 600 ft./lbs of torque. My car puts out a little over 400 torques. Durability is not an issue. Because of the time frames involved I don’t think there’s an issue with the speed sensor.

By “new tune” I mean that the shop that dyno tuned my car came out with revised/updated ECU software that addresses some shortcomings with the original software they gave me uneven idle, problems compensating for loads at idle (AC cycling mainly), and other minor things. What happens is that the shop emails you the “tune”. You get out your trusty hand held tuner (I use the Diablosport Predator, and highly recommend it). You plug the tuner to your computer and upload the tune from the computer to the tuner. Then you get in your car, plug the tuner into the OBDII port and upload the tune to the car. The whole process takes maybe 5-10 minutes.

Anyway, ABS light thing just started happening when the I uploaded the revised tune to the car. It only happens when I have the AC on and has only happened twice so far. I don’t think there’s a real problem with the ABS since it still works. And the ABS light goes off after a minute or so. I’m 90% sure the problem is with the new tune, but I can’t figure out how changes made to the ECU could effect the brakes. I could be wrong, but I don’t think those systems are linked.

I think the burning smell is your brakes engaging because of a problem with your new-found traction control. As you may know, Ford’s traction control works by retarding ignition timing and applying brake pressure to the spinning drive wheel. All of that makes use of the ABS system. So I’m just guessing, but I’d say:

New calibration that enables traction control + Burning smell + ABS light = Traction control problem.

I don’t think so. Whenever the traction control kicks in a green light appears on the dash for the duration of the event. Except for a brief instance where I purposely invoked it to make sure it was actually working. The light hasn’t come on, and aside from that brief test. There hasn’t been an event where the traction control would’ve or did engage. The smell was electrical. and was coming from dash, or possibly the AC vents. I had the AC cranked up all the way and the smell dissipated quickly.

No offense meant. Without this context and detail I had no way of realizing you had this depth of knowledge. We get so many posts about people reprogramming their ECUs with online purchased software and so many posts about people breaking their own vehicles that without knowing I assumed this fit into that category.

I guess I’d better start doing some research and come up wiith an idea to redeem myself…

UPDATE: I believe I have fixed the problem. Turns out the data pertaining to the tire revolutions per mile in the new tune was a bit off, it was set at 783 revs per mile. I changed the value to the correct number, 811 revs per mile. So far there have been no more random ABS lights appearing. Turns out the speed sensor does communicate with the ECU and the improper tire revs per mile probably caused some confusion.

I’m still at a loss to explain the brief electrical burning smell though.