throttle cutting out under heavy load (2 Viewers)

[kyoso23]

Here's what happens: First of all, I get ZERO CEL or any other symptoms. The truck runs great. However, especially when towing up steep grades, the throttle will immediately cut out. I can even feel it in the pedal. If I release the pedal and put it back down it's good to go again. It's very random, but mostly happens when I have it to the floor and the truck is under load (uphill, towing, etc...). No backfires, misfires, no CEL, it's really weird. Unfortunately it is a momentum killer when going up the passes with the trailer. I've only had it happen in 2nd or 3rd gear with it floored and at higher RPM. Anyone ever experience this?

EDIT: It's on a 1998

 

[TeCKis300]

How many miles do you have on the current spark plugs? Ever change the igniters?

These issues should result in a misfire code, though some times it will only be pending on not show up as a CEL. Trying seeing if there's any pending codes with a OBD-II scanner.

 

[ihadmail]

Cleaning the MAF sensor and the throttle body wouldn't hurt anything even if it doesn't fix it.

Clogged catalytic converters can also cause a loss of power when under a heavy load. To test them have someone gun the engine while in neutral and feel to see if the air exiting the exhaust increases proportionate to throttle input. This one kind of takes a bit of experience to really tell but if they're clogged bad it will be pretty apparent.

 

[kelly saad]

If you can feel it in the pedal then it sounds like it might be a problem with the throttle cable or where it connects to the throttle body. Check all those areas, pretty easy to see and get to. Have someone floor the pedal when its not running while you watch under the hood. Maybe you will be able to locate the issue if its related to the cable.

 

[huntsonora]

I have this exact same issue. Happened twice this week. It happened on my way home from NM and I filled up and took it to my mechanic a couple days later. We test drove it and it was fine but on the way home it happened again. Both times it happen I was at 1/4 tank. Filled up and tried to recreate the problem and it was fine

It's just weird. I don't know if the level of the fuel tank had anything to do with it but it was the only common denominator I could come up with

I'll let you know if I figure it out

 

[kelly saad]

I have this exact same issue. Happened twice this week. It happened on my way home from NM and I filled up and took it to my mechanic a couple days later. We test drove it and it was fine but on the way home it happened again. Both times it happen I was at 1/4 tank. Filled up and tried to recreate the problem and it was fine

It's just weird. I don't know if the level of the fuel tank had anything to do with it but it was the only common denominator I could come up with

I'll let you know if I figure it out

Toyota told me that the fuel pump is the one thing that wont kick on the engine light. Pump is in the tank so maybe its acting up when the fuel level is getting low.

 

[ih8everything]

I had this same issue multiple times on a 12 hour drive home from Arizona. It happened while in cruise control at 75-80mph whenever I approached a hill. It also happened when I really stepped on pedal to pass. Like you said, release the pedal or cancel cruise control and it's fine.

I haven't really tried to replicate it since then and I haven't had any issues. I was thinking it was an APPS or TPS issue.

Please post if you figure it out. Sounds like this affects a few people.

 

[WarWagon]

Could it be a bad coil pack? Had similar issues with a 4R I owned and it was a bad coil. CEL never turned on either.

 

[2001LC]

Here's what happens: First of all, I get ZERO CEL or any other symptoms. The truck runs great. However, especially when towing up steep grades, the throttle will immediately cut out. I can even feel it in the pedal. If I release the pedal and put it back down it's good to go again. It's very random, but mostly happens when I have it to the floor and the truck is under load (uphill, towing, etc...). No backfires, misfires, no CEL, it's really weird. Unfortunately it is a momentum killer when going up the passes with the trailer. I've only had it happen in 2nd or 3rd gear with it floored and at higher RPM. Anyone ever experience this?

EDIT: It's on a 1998

What's the RPM at "cut out"?

 

[jgray]

I was having intermittent throttle response loss and replaced the TPS (throttle position sensor) - it's been running great ever since...

 

[2001LC]

I was having intermittent throttle response loss and replaced the TPS (throttle position sensor) - it's been running great ever since...

Did you see a CEL or code?

 

[huntsonora]

Not to derail the OP's thread but here is a link to the symptoms I am seeing. I'm curious if his symptoms are the same...



This is a video of normal passing and I have 3/4 tank of gas and it doesn't hesitate....



My mechanic is leaning towards it being a fuel pump or filter issue since it's only happened when the tank gets down to 1/4 tank so far. To replace the filter I have to drop the tank and if I have to do that I'll probably just replace the pump while I'm in there. It's a $600+ job and I hate to throw good money at parts but I can't think of what else if might be at this point

 

[jgray]

Did you see a CEL or code?

This used to happen randomly with no CEL often months and months apart. I checked the throttle cable, cleaned MAF sensor, etc in the past but always suspected it may be related to the TPS. Finally it got worse and started happening more frequently and finally threw a CEL code that I was able to catch with my reader before it went away. Code thrown ended up being - P0120 - TPS / Pedal Position Sensor A circuit malfunction. I just ordered a new TPS and it's been running perfect ever since (replaced back in March of 2016).

 

[kyoso23]

Thank you for all of the suggestions guys, I replaced the TPS a few years back for another issue but I think I might give that a try again. It's the only thing that makes sense. Fuel level, etc...has never made a difference and I have yet to get a CEL. It started to only cut out above 4k RPM but my wife said it cut out yesterday when she went to leave a parking space. I'll report back when I get around to doing it.

 

[kyoso23]

I replaced the TPS again, no dice.

 

[bctlex]

My mechanic is leaning towards it being a fuel pump or filter issue since it's only happened when the tank gets down to 1/4 tank so far. To replace the filter I have to drop the tank and if I have to do that I'll probably just replace the pump while I'm in there. It's a $600+ job and I hate to throw good money at parts but I can't think of what else if might be at this point

No need to drop the tank according to this:

Thank You Toyota! ...Fuel Pump Replacement.

 

[Dwight S]

I'm leaning toward coil pack since you mentioned pulling out of a parking spot. Also would consider spark plugs if you haven't changed them.

 

[2001LC]

^^ Should see a CEL soon.

 

[Dwight S]

^^ Should see a CEL soon.

Yeah... I'm sure there is a way to check a coil pack to see if it is on its way out, but I don't know how. When I feel the first symptoms, I buy one and keep it handy in the truck and change it when it goes. Love having a Scan Gauge II hooked up.

 

[2001LC]

I've been gather some good and bad coils to have some test run, just for this reason. Just haven't had time yet to take to next step.