mpg

Howdy folks,
Had the second occurrence yesterday of my gas pedal stopping halfway while driving on the freeway. Can't seem to find any mention of this or info on it.
Truck will run fine (albeit with some loud pinging under load), after 30 mins of freeway driving I'll only be able to press the gas about halfway before it stops.
Can still give it enough gas to accelerate, very slowly, but maintain highway speeds. Curiously, it seems to stop just before the point at which the engine pinging is worst.
I'll bring it to a stop, turn the truck off, and after a few seconds the pedal will unlock and return the full throw.
The rest of the day the pedal operates just fine.

Is this a function of the ECU, what even is the mechanical function at work?
Thanks folks

ksti

What vehicle are you working on? year, model motor?
Did you lift the hood and check the throttle cable to see if it's binding?

mpg

Geez amateur hour, sorry: 1991 Pickup 22RE Manual 4wd

Checked the throttle cable, no apparent binding.
Strange that the pedal seems to hit a wall, then has a full release when the truck is off.

ksti

I wouldn't have asked the silly question had you included it your post.

mpg

ksti, that was supposed to be self-deprecating, sorry. I'm the amateur here, new to the forum. Trying to get into the routine!

ksti

No worries.
But I have never heard of a gas pedal acting that way because of the ECU.
I'm just wondering if your cable is frayed on the inside maybe causing intermittent problem.
The cable adjustment shouldn't change randomly.
You also might want to check from the gas pedal to the throttle body for some kind of obstruction.

dropzone

iTrader: (6)

go to the user CP
edit options, select signature and add your info there.
that way on future issues you already have it and don't have to remember it if you have another thread looking for help

and don't worry about it, old timers forget to give similar info

mpg

thanks dropzone!

scope103

As ksti says, there really isn't anything ECU-driven that affects the throttle. So a sticking gas-pedal is almost certainly a mechanical problem (frayed cable, loose piece in the stops on the throttle plate.)

The fact that it "clears up" when you turn it off is probably not related, but who knows? The only thing that could contribute to that is the throttle unloader (when the engine vacuum disappears, this allows a spring to push the throttle plate open a little. Probably to stop dieseling.)

ewong

interference from the throttle cable used by the cruise control?

wyoming9

iTrader: (1)

This makes no sense at all that it happens once then it is good all day

Does it get stuck ??

You just can`t depress it pass a certain point ??

Look to make sure the firewall is not cracked putting pressure on the cable

Cruise cable is good idea since mine are all removed

Then with the cruise control if your foot engages the throttle or brake it cancels the cruise till you hit resume I think

Can`t wait to see how this plays out

highonpottery

iTrader: (1)

When I first bought my truck it was having weird gas pedal issues - like it was kinda jammed going from idle to accelerating, then it would release and be fine. I inspected everything starting at the pedal itself......ended up being a gunky funky throttle body jamming up the butterfly/plate/flap thingy and has been fine every since I cleaned it. Try cleaning your throttle body with cleaner and a toothbrush

mpg

Hey all,
Cruise control!
I've neglected to think about the aftermarket cruise control a PO installed, since I removed the control arm from the steering column (never use it, knee kept hitting). Will have to figure out a full delete, makes a lot of sense that it would interfere but still don't understand what function or malfunction would activate a "wall" on the accelerator.

Ruled out mechanical error (fraying/throttle body) by the way it "turns on/off" very deliberately, also fully cleaned TB and replaced gaskets a few months ago.

​Thanks all!

scope103

Let's just say that between the Throttle Position Sensor, the Throttle opener, the Dashpot, the accelerator cable, the transmission Throttle Cable, and the Cruise Control actuator cable, there's a whole bunch of stuff hanging off the throttle plate. If anything (abandoned cheap-ass cruise control connection?) should shift around and get under something else, you won't be able to push the accelerator pedal past that point (until it wiggles free again).

mpg

After a minor revelation, it turned out to be the dashpot set screw. Lock nut wasn't tight enough, and the screw would work its way out until it contacted the throttle body on the upswing. Replaced with shorter set screw, won't ever be bothered again.

wallytoo

iTrader: (1)

thanks for providing the details about what caused the problem, might help someone else later.

RAD4Runner

Second that!
MPG,
Awesome. Proof once more that Toyota components are bullet-proof; problems arise from poor wiring/connections, assembly, and/or maintenance.