Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec The 3L is up and running!

3L Hybrid SVT
SVT heads/cams & intake manifolds(2.5L)
SVT MAF(stock for me)
39# 03/04 Cobra injectors
65mm Mustang GT throttle body

I've checked for intake leaks, replaced the UIM/LIM gaksets, EGR gasket, cleaned the IAC, etc. I'm going to try cleaning the MAF wires to see if that helps. If not, I don't know what else to try, other than work with the tune. I don't hear an intake leak anywhere, have done the soapy water test on everything that I thought could be leaking. Everything looks great.

I don't know what was done with the tune, as I ordered my Xcal2 through Brenspeed. My dyno graphs look awesome, but maybe there is a little work to be done at idle.

Mark

Is your MAF stock? Are your injectors 24#?

You can tune the car by adjusting the MAF curve so that it gives you good WOT A/F and power, but in so doing you may be screwing up the non WOT driveability.

Because of this you need to use the stock MAF and leave the stock MAF transfer function, then adjust the commanded air fuel from the fuel base table to pull or add fuel as necessary.

If it is not a stock MAF then the challenge will be in accurately figuring out the MAF function.

Isn't the SVT the same as the other V6's MAF's. That's what I've always read here. Wouldn't make sense since SVT's have larger injectors. I have an SE MAF on my SVT right now. No issues.

Todd, I can't answer that. From what I've seen there have been different MAFs on the same year and model of car, the calibration numbers being different.
This isn't a big deal as the computer can adapt to these different calibrations easily enough if you had to change it and if it was the only change.
As far as the 'size' of the MAF, regarding its airflow capability I would think all of the 2.5 MAFs would be pretty similar, in the 700 kg/hr range.

However, if the chip/tune has disabled the learning features, or if the maf calibration is off just enough combined with the added effects of different manifolds or hardware, displacement, TB size, etc., then I'd say it could knock it far enough out that you'd get driveability issues.

The biggest factors I've found in tuning this engine were:
the maf calibration and getting it correctly entered into the computer,
throttlebody size and amount of leakage past the throttleplate,
length of the intake tract between the MAF and the TB,
PCV system routing,
injector size.

Some of these are easy to fix, some not. The TB sizing issues can be hard to solve if you have a leaky throttlebody. I've even filled in the pre-drilled hole on most of the larger TB plates to reduce airflow at idle so the engine will be able to drop down to 700rpm range. I had one TB that was leaking around the shaft bearings enough that it would idle at 800-900rpm even with the IAC tube pinched completely shut.

The only way to determine the throttlebody leakage issues (assuming you have no manifold leaks) is to plug/pinch the IAC line and Plug off the PCV line so that they don't introduce any more air.
If the engine stalls out, then the PCM should be able to control the idle by adjusting the IAC. IF it will still idle with the IAC tube pinched off, then how high is the idle and try plugging the PCV line off. Eventually you can determine where the air is coming from and work on it. THe troublesome TB that I had gave me lots of grief until I installed sealing o-rings with grease onto the shafts on the outside of the bearings. THe it worked like a charm.

If you try to order a MAF drom Bill online. There are only 2 MAF's listed. 2L and 2.5L just as an FYI so this would prove V6's all use the same MAF.

To determine if the MAF is at fault, couldn't he just unplug it?

but all the maf's arent the same,if you have access to the full SCT software you can look this up,when i had my car tuned last year the tuner showed me the difference between the svt maf program and the stock duratec maf program,they are different in tune,but not size obv'ly

Update:
Today I found a vacuum leak on my UIM using carb cleaner. It is still idling rough, but would completely smooth out every time I hit a certain spot on the gasket between the UIM and LIM with carb cleaner. My bro and I will be taking off the UIM tomorrow and inspecting the gaskets.

Other than that, my only other concern is a slight hesitation/bogging between 2k and 3k RPMs under partial throttle (usually closer to 2k). That and there still feels like there's an IMRC in my car . In other words, I still feel a jump up in power around 3k RPMs. Above 3k the car hauls balls though! It seems to me that only more tuning needs to be done (after fixing this vacuum leak of course!).