One thing that comes to mind for me is perhaps the TPS has a dead spot in it. You can test it with a multi-meter if you have one, or if you have a scan tool that can read throttle position you could use that the check it as well.
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
I have to agree, my Duratec feels the same. It seems to "bog" when I flog it, then seems to "catch up" as the RPMs increase. The car does seem faster at "just-less-than-wide-open-throttle".
My theory on this is that at WOT, the O2 sensors shut off, and the car uses only the MAF + RPM to determine how much fuel to add. Since there is no "check and balance" of the pre-programmed fuel curve, the car may be running rich or lean (from my experience, the Focus runs a little rich at WOT).
However, it's better to run a little rich for engine longevity. You may be making a few less horsepower, but it is SAFER horsepower.
One thing that seems to help is to "roll" into the throttle. Don't just "punch it." Give it a little more and more until you are at WOT. Also, don't let off between gears. Once the hammer is down, keep it down, use the clutch and a strong arm to change gears.
Note that I am not reponsible if you mess up your car- this is not good for the car in any way. If you plan to do this a lot, invest in a good set of poly or even solid motor mounts.
____________________ Project FocusFast
'06 ZX3- Intake, exhaust, mount
'01 ZX3- Salvaged, SOLD
'01 ZX3- Repo'd several years ago
'80 RX7 SA- Where the f*** did THAT come from?
They were designed to shut off under WOT. Pretty much every car does this. I'm not sure exactly why, but I can give some explaination as to what is going on.
During non-WOT driving, the ECU continually adjusts air-fuel ratios. Ever seen a narrowband a/f gauge? It bounces back and forth, like an alien spaceship. Under WOT, it basically stays still, at the ECU's "set" a/f ratio.
____________________ Project FocusFast
'06 ZX3- Intake, exhaust, mount
'01 ZX3- Salvaged, SOLD
'01 ZX3- Repo'd several years ago
'80 RX7 SA- Where the f*** did THAT come from?
The O2 sensors dont turn off. That would be near instant death for an engine if they did. I have scanned a lot of cars at WOT and none of them have had the O2's shut off.
What does happen is that your LTFT (Long Term Fuel Trims) 'lock' in when you go WOT. In nearly all factory set ups the LTFT's lock in rich. As PFF stated, you would rather be rich on fuel, to an extent, than lean. Being overly rich can cause issues as well, particularly with Knock Retard.
That said, the Focus is pretty unique in its tuning. It is the only car I know of on the market, even in Fords line up, that is un-naturally lean, and I dont mean just a little bit either. And from what I can tell it seems isolated and unique to the Focus. I dont know for fact if the Duratec motor suffers from this kind of factory tuning, but the Zetecs, including the SVT's, do.
If the Duratec is tuned like this, it is very likely that the condition is inducing KR and the computer is pulling timing. Whereas if you roll into the throttle is not such a sudden change and you avoid the LTFT lock longer the motor responds better. Since we have two owners observing the same condition, then I would believe less the TPS is the issue and more that tuning is.
PFF, sorry to disagree with you, but I have never ever seen a car turn off the O2's. Ive had a computer hooked up to Fords, Dodges and GM vehicles and never once have I ever seen O2's turn off.
You MAF outputs a specific frequency based on the air it sees. For instance, on the Grand Prix, the MAF tops out at 11,500khz. After which the computer can no longer compensate for the air coming in and you either have to upgrade or use different MAF tables. Even MAF and RPM would be poor at best in determining fueling as there are such load variances.
I can even show you my latest track runs in which I was scanning the car and show you that the O2's dont turn off. Ideally, you want your LTFT's to lock in at 0, but it takes tuning software to do that. At best, you could use an aftermarket chip to help out, but even with that they have to be conservative in the tuning as things vary so much from car to car and the variance to climate and so on.
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
You're right- they don't "turn off", they just stop reading them, and use the LTFTs. That's what I was trying to describe, just with my lack of terminology.
But from my experience, Zetecs tend to run rich under WOT. I'm not the only one who's noticed this. I kind of assumed Duratecs were the same.
Regardless of exactly what the issue is, wether it be a rich or lean condition caused by the LTFTs, rolling into the throttle does seem to cure it a little.
I might try running some premium gas next time I fill up and see if that helps, too- if it is a lean condition and the ECU is pulling timing because it's getting knock, a higher octane fuel could help.
____________________ Project FocusFast
'06 ZX3- Intake, exhaust, mount
'01 ZX3- Salvaged, SOLD
'01 ZX3- Repo'd several years ago
'80 RX7 SA- Where the f*** did THAT come from?
It doesnt stop reading them either, the O2 is the computers only way to know how to adjust fueling. When you go WOT and the fuel trims lock in the computer reads the O2's in order to tell if the LTFT's are locked in properly, if they are, the computer will then use the information from the O2's to adjust timing. Too lean or too rich are not good, though a bit on the rich side is better ultimately, but even too rich, there is a limit the computer can adjust timing to prevent KR.
My last track pass I was running too rich, but a good margin as well. I started out with 18.5 degrees of timing and crossed the line with 12 as the computer tried to adjust for the extra fuel that was causing Knock. Every degree of knock costs you in the area of 2 - 3 hp and I hit nearly 5 degrees. Only briefly though, but once you hit it, the computer is VERY conservative in returning the timing, it will yank it in a heartbeat but can take about a second, to second and a half for every degree of knock to return to normal, and by the time it does the run is over with.
If you are seeing the Focus run rich, I would love to see the data, at WOT, I have yet to see one run rich and as I mentioned it seems to be a little on the danger side of running lean, and it seems specific to the Focus line, but the Duratec I have no data on directly, only the Zetec and the SVT which are essentially the same engines.
But you are correct, if you run a higher octane and notice a difference then it would show one of three things, either its running lean, or getting KR or a combination of both, most likely both.
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
No, its not because the O2 shut off, they dont do that. I do think it perhaps is something to do with how the PCM responds to sudden demands.
Im going to try and get some screen shots of the tables and information that is programmed into a PCM and see if that will help clear things up some. I wont make any promises but I'll try and get it done this weekend.
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
it's the difference between open loop and closed loop. At every point except WOT, the car is in closed loop, which means that it is recycling a portion of the exhaust gases (remember that EGR thingy? ), at WOT, the car goes into open loop, and stops recirculating, this inevitably changes the AF mixture at the very beginning of WOT.
This primarily happens in first gear from a standing start only, and it happens typically because of the severe difference between idle recirculation and WOT, essentially the car will be sluggish and lean and hence the lag. I've not seen this be a problem once the car is above idle, and it doesn't show in the dyno's below.
), at WOT, the car goes into open loop, and stops recirculating, this inevitably changes the AF mixture at the very beginning of WOT.