Lost Torque on Highway this Morning (1 Viewer)

[87warrior]

Another very cold day in Denver, same issue popping up. CEL popped on then suddenly lost power.

Full press of pedal and I could at least move. Guess I’m back at it!

Did it pop another APPS code? Did you ever replace the APPS after the first CEL was triggered?

 

[jackhossross]

Did it pop another APPS code? Did you ever replace the APPS after the first CEL was triggered?

Same code - time to do it!

 

[Mike NXP]

Did it pop another APPS code? Did you ever replace the APPS after the first CEL was triggered?

What is APPS? Does it have to do with throttle body and stuff up there?

I wonder if my 02 is drive by wire or not. I have a physical cable going to the throttle body which is nice but then I see some electric doo dads.

 

[87warrior]

What is APPS? Does it have to do with throttle body and stuff up there?

I wonder if my 02 is drive by wire or not. I have a physical cable going to the throttle body which is nice but then I see some electric doo dads.

The APPS is the Accelerator Pedal Position Sensor. On the early 100's with a throttle cable, this is where the cable terminates at the throttle body. There is an electric motor that opens and closes the throttle plate (butterfly) on the other side of the throttle body... If the APPS or throttle motor dies, the throttle cable can engage the throttle plate in the last 10% or so of cable travel through the APPS linkage. The Throttle position sensors (TPS) is on the other side of the TB and checks how far throttle motor is opening the throttle plate.

In the case of the OP, a failed APPS would not register throttle input and would not tell the throttle motor to open the throttle plate, resulting in a loss of power. However, if the throttle was 'floored', the throttle plate would mechanically open a small amount through the APPS linkage. This mechanical failsafe would provide some drivability.

 

[jackhossross]

The APPS is the Accelerator Pedal Position Sensor. On the early 100's with a throttle cable, this is where the cable terminates at the throttle body. There is an electric motor that opens and closes the throttle plate (butterfly) on the other side of the throttle body... If the APPS or throttle motor dies, the throttle cable can engage the throttle plate in the last 10% or so of cable travel through the APPS linkage. The Throttle position sensors (TPS) is on the other side of the TB and checks how far throttle motor is opening the throttle plate.

In the case of the OP, a failed APPS would not register throttle input and would not tell the throttle motor to open the throttle plate, resulting in a loss of power. However, if the throttle was 'floored', the throttle plate would mechanically open a small amount through the APPS linkage. This mechanical failsafe would provide some drivability.

Well stated. Exactly what is happening.

 

[Campfire]

Going to revive this thread with the somewhat the same symptoms. Traveling up the wonderful Highway 5 of California on Sunday and started having that loss of power at 2,000-2,600 RPM after letting off the pedal. Had another 80 miles to home, so I thought I would narrow down the conditions.
If I "floored it" it would come back and be OK for a while, but then I noticed it would do it every time. Felt like I was running out of gas, but it would just drop to an idle and not die, while feathering the pedal made no difference.
HOWEVER.... I could set the cruise control and it would stay at freeway speed and I could use the cruise to accelerate and decelerate with no issues.

Going out today to do some resistance checks on the APPS since the motor would still set the throttle with the cruise control.
(EDIT)----- No check engine light, and no codes present.


Again, thanks to this community for pointing me in the right direction. Updates coming soon.

 

[Campfire]

So after researching the APPS a lot, pulled out the service manual and did the resistance checks. FLUKE meter showed 2.2k (within the 1.8-3.2k ohms spec) until I wiggled the second pin. Had a spike, then a loss.
Sprayed some electronic cleaner in the connector and tried again, seemed to help. Re-assembled and have about 35 miles on it with now failure yet. Holding off dropping $500 for the throttle body at the moment.
And I guess my '99 doesn't want to throw a P1121 code, so I'm going to wait this one out for it to have a more constant failure.

 

[Jack90210]

I might be jumping the gun here but just wanted to pass on some info...

The throttle body from Toyota is around $500 new and includes the miscellaneous sensors everyone is talking about. If you can swing it, you may consider just replacing the whole unit instead of messing with each item. They all go bad over time as well as the mechanical components inside the throttle body itself. In the long run, it will be cheaper and less of a headache to replace it all in one go. Well, if the price doesn't keep dropping. The TB was ~$1k not even 10 years ago, it was $580 when I bought it 2 years ago, and now it's down to $490.

Old thread I know, but the throttle body assembly is $340 (for later-year trucks) from Ourisman of Richmond (formerly McGeorge). Can't imagine it'll drop much further unless the yen totally tanks.