What happens electronically during WOT

[mh87BroncoII]

What does the ECM do under WOT?

i.e. does it shut down EGR? Does it increase fuel pressure? Does it turn off O2 sensor? Does it reset any critical sensors such as MAP?

---Marty

[turret_plug]

What engine do you have? 2.9 EFI?.... The only thing I know of with that engine, is it allows full fuel flow from the pumps and injectors.... I have a 2.9L and I can tell you from experience....... hardly anything happens at WOT with that slow ass engine......

[mrshorty]

Here's what I know:

1). the computer doesn't have any control over fuel pressure. Fuel pressure is modulated, however, by engine vacuum, so fuel pressure will increase in response to the low vacuum
2) It ignores O2 sensor
3) It still calculates timing advance and sends that to the ICM. If it detects any ping/knock via the knock sensor it will retard timing to eliminate the knock.
4) I'm not sure what it does with the EGR system, whether it just holds the EVR solenoid full open or not.

[mh87BroncoII]

Mr Shorty - thanks for chiming in...

I have heard on other sites that EGR is not activated during idle, WOT, low external temps (due to throttle plate icing), and some other time. It makes sense, as the ECM shouldn't care about NOx during hard acceleration or idle.

[McQue]

If your hesitation is clearing up after WOT, it makes me think there may be an 02 sensor problem...for instance...what if 02 sensor is giving bad feedback...say your running rich...then you try to accelerate normal..more fuel, even richer, your motors hesitates, then you go to Wide open throttle...02 sensor is ignored...air and fuel mixture gets better, timing gets advanced, motor recovers from hesitation....02 sensor gets hotter from the WOT fuel burn off and more reactive, starts sending feedback to lean out the fuel system...

wouldn't be the first time an 02 sensor was causing hesitation problems.....

[mh87BroncoII]

McQue,

I think you're right, but I wonder why the hesitation also stops during idle (ie at WOT and idle). I would suspect a faulty O2 would give good drivability at WOT and not idle, or visa versa. dunno...

Anyways, a new O2 is in order as I would venture to say that it's probably 20 years old already...

---Marty

[mh87BroncoII]

Problem fixed -
See reply under 'BII Hesitation' thread.

---Marty

[tbolt 460]

why didnt you put it here???

[lawnboy58]

My 88 bronco ll idled great & revved great under no load but under a load it had a big dead spot as soon, as you floored it, it was fine, replaced the o2 sensor and fixed the problem.