Experiencing an issue with acceleration while at WOT

[Ziggy75]

I posted a thread similar to this regarding this issue but was more directed to the transmission because the transmission was slipping. After adding fluid I found a different issue that was hidden while transmission was slipping.

At highway speed if I press gas pedal to WOT the transmission downshifts and rpm's go up. Once this happens the power is totally cut out and then the transmission shifts back to the higher gear. After it shifts back into OD it will then downshift again (because pedal is pressed) and rpm's climb back up. Once it downshifts the power is cut out again. Almost like a rev limited or traction control is pulling power.

I hooked up my Actron scanner and was viewing some parameters. When this situation occurs my Absolute TPS % goes from 75% down to 22% and back up to 75% and so on. Now my curiosity (and frustration) has gotten to me. Why would TPS jump all over the place. The TPS is a messenger of that the location of throttle plate is showing. If the TPS is in fact seeing the plate moving, why is it moving? I have the pedal pressed to the floor. It shouldnt be moving. Also, if pedal is pressed to the floor, why is it reading at 75% and not 100%? So either the TPS is wacked out or it is actually reading the plate move which would then indicate the throttle plate is not staying where it should be. I pulled the plastic air tube off throttle and turned key forward. I had my kid press pedal and the plate did open all the way. When plate was open full I was hearing a buzzing sound coming from throttle body actuator motor. Is this normal? Do you think I am looking in the right direction or do you think I am way off? If I am looking at it wrong then why does TPS read all over the place during condition?

 

[J_Train]

It could be the throttle body. We do quite a bit of throttle bodies at the dealership. Explorers, F150's, 500's, and Focus, those are the common ones. But if you want to try a tp sensor since its cheaper it's not a bad idea.

 

[swshawaii]

Did you pull any of these trouble codes? If so, almost a certain TPS issue.

P0120 Throttle/Petal Position Sensor/Switch A Circuit Malfunction
P0121 Throttle/Petal Position Sensor/Switch A Circuit Range/Performance Problem
P0122 Throttle/Petal Position Sensor/Switch A Circuit Low Input
P0123 Throttle/Petal Position Sensor/Switch A Circuit High Input
P0124 Throttle/Petal Position Sensor/Switch A Circuit Intermittent

http://www.explorerforum.com/forums/showpost.php?p=2054355&postcount=2

 

[Ziggy75]

The only code is a p0446 which I am trying to eliminate. Other than that, no codes. I suppose I could try a TPS. I just hate throwing parts at something. Can I check the TPS with a volt meter to see the range .998 - 5v? My 94 Mustang is checked that way. Wasnt sure if the new ones were any different. If it does check to 5v wot, then the actron should show 100%.

 

[swshawaii]

Test it, p0446 doesn't sound related to your shifting issues. EVAP system?

http://www.explorerforum.com/forums/showthread.php?p=2349296

 

[Ziggy75]

Thanks for providing the link.

 

[swshawaii]

Agree, changing non-returnable electrical parts can get expensive fast.

 

[Flag Gibby]

Get rid of the P0446 (evap issue) and then see if it goes away. The emissions systems can do really weird things to an engine at WOT when they are not working properly.

 

[Ziggy75]

I haven't been able to physically test the tps yet so I don't know what reading I will see but I do remember seeing something in that link regarding if the sensor reads at a low voltage that the fuel tank pressure sensor could have a short. I wonder if a p0446 could result from a short in the fuel tank pressure sensor.

 

[Ziggy75]

I was able to test the tps. I received a range of .880 to 4.20. Is 4.2 too low? I was always under the impression that I should receive close to 5.0 volts. I cycled the throttle plate while watching my actron scanner and didnt see any jump or drop in % during its range. I then went to the gas pedal and checked it. I was able to look at the accelerator position that is given in the scanner and no drop. This was all with the car off/key on. I am about to give up on this.. I think I need to take the advice of getting the evap system working properly and go from there.

 

[Ziggy75]

So tonight I was dropping off the mother in law and while driving home I was watching my actron scanner and viewing some parameters while the engine was cutting in and out. I was driving in some snow that was approximately 7 inches on road and then all of a sudden the wrench light came on. Once this happened I had zero power. The transmission also stayed in a gear and would not down shift or upshift. It seemed like it might have been 2 gear. Anyway, it felt like the parking brake was on. So I pull into town and check codes. I got a U1900 and a not communicating with transmission module. I cant remember the code. I cleared codes and started it up. It ran fine and I drove it for approximately 5 miles and the codes did not come back.

 

[Flag Gibby]

I have had a similar event and it ended up being ice on the ABS sensor and another time a missing tooth on the ABS snap ring that somehow broke off in deep snow. I wouldn't think too much about it unless it happens again in the next few days.

 

[Ziggy75]

I am thinking the same thing. I will keep the scanner in the car just in case the code comes back. Driving with one gear wouldnt be a good idea.

 

[Flag Gibby]

When the ABS sensor completely looses the signal then the vehicle goes into limp mode so you can still get somewhere but not very fast. I have had this happen once when one of the ABS snap rings came completely off and I had to drive the vehicle to the dealership since the vehicle was still under warrantee and I happened to be only 1 mile away from it.