Detonation after mail order tune

[stangGT97]

I ordered a SCT SF3 tuner with a custom 93 octane performance tune, and I have been running 93 for the last 5 tanks. Here's the deal - I loaded up the tune following the included instructions, then took her out for a spin. Under light throttle, the car felt much stronger to me, but once I gave it over 50% throttle, I could hear detonation, in all gears. Getting onto the highway, I couldn't get my car to go over 70 in 5th gear, and I could hear the detonation pretty clearly. Luckily had the presence of mind to bring the tuner with me on the trip, so I pulled off the highway and returned the car to stock, thereby eliminating the problem

My car is basically stock, with the exception of the PI intake (which I included on my mods list when ordering the tune). I'm pretty baffled as to how this mail order tune could be so far off. What could have gone wrong? The instructions said the battery should be disconnected on 94-97 mustangs to reset the keep alive memory, should I have done it as well even though mine is a '98? Should I request a new tune or go elsewhere? I was thinking I could modify the tune but I'm not comfortable playing with those parameters.

Thanks in advance for any advice

 

[04YELLOWGT]

If it has user adjustability I would pull the timing out of it and add some fuel and see if that helps. I would call the place you bought it from and tell them you want a new tune too.

 

[stangGT97]

Thanks - I'll give them a call and see what I can get done

 

[TheDukeOfEarl]

Mail order sucks. Put it on a dyno. You have already done damage to your engine. The dyno is cheap compaired to a new engine.

 

[BlownFiveLiter]

Mail order sucks. Put it on a dyno. You have already done damage to your engine. The dyno is cheap compaired to a new engine.

I'll agree with the first part, but unless you're pissing coolant out your tailpipe, have no compression in a cylinder (or several), or have a milkshake in your oil, there's no damage done yet. You are increasing the risk of damage by detonating, however, so running the stock tune is a good idea.

The problem with a mail order tune, no matter who it comes from, is that not one car is identical. If you took 10 cars with identical running conditions and compared sensor readings from each car, you'd probably have 10 different readings. Most mail order tunes try to compensate for that by being a bit on the conservative side, but again, the limitations of not having the car physically in front of them on the dyno means you don't really know what the sensors are reading, and what adjustments the EEC is going to make based on perceived values. If you're able to get another tune out of them with less timing, that would be the way to go. Ideally you should toss it on the dyno, though.

 

[stangGT97]

Well, the car is basically stock and was running fine without any sort of tune - I got the mail order tune only because I bundled the SCT tuner with my 4.10s and saved some money. Ideally, I'd like to dyno the car but in it's current state, it probably isn't worth it.

As far as engine damage - I don't feel any power drop after returning it to stock, still got 28mpg highway with my crappy 2.73s. Probably ok? I'll pull a plug this weekend to verify.

 

[TheDukeOfEarl]

The damage caused by pre det isnt easly noticable. The damage is done to the life of the bearings. Every time you get a pre det you are hammering the bottom end. It may show up right away if its serious enough or maybe later with a early failure. Pre det is bad...Mmmmmmk

 

[347_stang]

If you're serious about tuning it still get it on the dyno!

 

[stangGT97]

I know it's serious, which is why I pulled off the road to return to stock. I tried the new tune they sent me, it still sucks. Car is staying stock tuned until I can find a good dyno here in upstate NY.