BornToFord

I have a 2002 GT with 93k miles. Mods are a K&N CAI and a Magnaflow full exhaust with cats. It was my son's car and it always ran stinky rich, even 7 years ago. I used to tell him to get it looked at, cause I hated to drive it. Now I own it!

I replaced the plugs, COPs, PCV valve, MAF, and o2 sensors. It does run much better after all of this, and it runs great until fully warm. After it warms up it runs rich. The dealer checked it out and said the A/F ratio was about 11.5-12:1. They said the engine is sound (and I agree).

I have an SCT TSX tuner and flashed the performance tune and it seems a little better, but still not right.

Is the ECU not interpreting the input properly and setting me up rich? Seems like that is the only explanation at this point.

Would a dyno tune fix this, or would a new ECU be the answer?

Anything else to try?

My plan is to get it running correctly, then do some engine mods.

cliffyk

You need to find a good diagnostic shop, someplace other than a dealership that checks it out and pronounces that "...the A/F ratio was about 11.5-12:1.", and apparently offered nothing beyond that.

Are you 100% certain the replacement MAF you installed was a functional duplicate of the stock unit?

What make and model is it?

Have you tried installing the original MAF? (disconnect the battery for 5-7 minutes while doing this)

Have the O² sensor outputs been checked with an oscilloscope? The output should look like this:

at idle:


at 2k RPM:


If the sensor outputs are very low (1/2 or less of as shown above), the sensor heaters and heater voltages need to be checked.

You said in another post that you used NTK sensors, what part number were they? I'd like to check that you got the correct sensors.

BornToFord

Thanks Cliff,

o2 = NTK 22060

MAF = Hitachi 49-00161ON (Supposed to be OEM)

I noticed no real difference in the MAF. I did not reset the ECU when I did the swap however.

The o2 sensors have not been tested. Not sure who would be capable around here.

cliffyk

Those should be the correct sensors, I do not know about the MAF as I cannot find a trustworthy cross reference for it other than as replacement for the F-150 and a few eBay and BuyAuto (whom I do NOT trust) mentions of the Mustang.

Its appearing similar to the stock MAF is good, however that does not mean its transfer curve is the same. Do you still have the stock MAF, or can you borrow one? To my mind it would be worth swapping it out if possible.

As to clearing the KAM, this should always be done when replacing, cleaning, or even just removing and re-installing any engine control or emissions related sensor or other device. It is also a good practice to disconnect the battery whenever working on anything electrical--in the factory manuals this is always step one, though I admit I do not always do so...

BornToFord

Hey Cliff, from what I can find after searching the Motorcraft p/n the same MAF was used on many of their 4.6 engines. I think this one is correct. (?)

I had the original MAF installed when I had the car at the dealer and they did their testing. At idle I could smell that it was fairly running rich, and of course it was running pretty rough.

The new MAF seems to have cleared up the rich idle condition after having reset the ECU. It has that occasional lean pop at idle now, so I'm confused at this point.

I shot a quick video of the car at idle, and then from the cab while driving. I have toothpicks shoved in the air vents, and you can still hear them rattle at higher engine speeds. At WOT it still has excess vibration. The car just runs rough and is making me nuts. These engine controls are baffling!

cliffyk

I don't hear any misfiring or anything else untoward in the engine, and think it's the exhaust system causing the vibration--though you may want to check the motor and transmission mounts.

The muffler placement on our cars can cause some serious sympathetic resonances (harmonic vibrations) in the cabin. The most well known of these is the "drone" at 2000 to 2200 rpm, with chambered mufflers it can be overwhelming.

BornToFord

Interesting, the trans mount is new. I just had the T56 installed. I bought some poly motor mounts and haven't installed them yet. I should get it up on a rack and have it checked out.

You have the same exhaust pretty much (magnaflow complete), don't you Clff? Do you have vibration issues? Maybe I've just been driving the wife's Infiniti too much and am getting soft?

It may be time to start with the bolt ons and get a real tune.

cliffyk

My exhaust setup is quite similar, though it does not seem as loud as yours--maybe I am just used to it?

I wonder if the tranny mount was improperly installed, or if the exhaust is hitting something? I had to "persuade" the passenger side headpipe with a 2 lb ball peen. dimpling it so it would not hit the chassis.

In your other post you reported the dealer saying the AFR 11.5:1 to 12.0:1 and I assumed they meant in closed-loop mode. However if was that at WOT and/or high loads (which most dealers do not test) and you still have the stock tune, then it is "normal" as the stock tune tends toward pig-rich at WOT (the ignition timing is far less than optimal as well). I have always suspected this was deliberate to make 110% certain the engine would run on whatever crap got into the tank, and that there was nothing anyone could possibly do to hurt the engine while under warranty.

That is why I recommend a good tune (even a mail order tune) as the first mod, after only perhaps opening up the exhaust. A decent tune will get the WOT AFR back in line at 12.5:1 to 13.0:1, and even when configured for 87 octane swill will bump the timing by 2° to 3° or more...

BornToFord

Thanks for the info Cliff. I'll check out the trans installation.

I am running a 91 octane tune from Bama that came along with my SCT TSX tuner, that uses my Android tablet. I seem to be pulling pretty strong at WOT.

I had thoughts of supercharging but I think I probably should rebuild the engine since it has 93k.

I like what you have done with your ride, so maybe that would take care of my need for speed for a while. A new TB and plenum would be cheap and easy. Would you do anything different? You still like the PP parts? Are you using the stock MAF?

Thanks for the help!

cliffyk

Not the same vehicle, however I supercharged my '90 Miata at 220k miles and ran it at 8-10 psi for over 100k more. Check the compression and manifold vacuum, then if the engine is tight go for it.

I remain pleased with the Pro Products stuff (they are the same base design as Trick Flow's line, however the Pro Products have smoother castings):

Pro Products plenum:


TrickFlow plenum:


The stock MAF can meter up to 1100 kg/h (2420 lb/h) without pegging; that's 380 fwHP, more than most n/a builds will lay down.

The stock injectors are a weak point, especially the 19 lb/h orange units. They are pretty much maxed out at the factory rated 260 fwHP, that's why Ford changed over to the pink 21 lb/h injectors in late 2002 (you '02 may have the pink injectors). At 260 fwHP and 39.15 psi the pink injectors are running at a bit better than 85% duty cycle, add much of any power and they are at 90%+.

At 85% d/c the 21s can push 285 fwHP. I am running the FRPP 24 lb/h injectors and with the 262 HP at the wheels (a guesstimated 308 at the flywheel assuming a 15% drivetrain loss) they run at 80% or so.