1FZ-FE Slight Loss of Acceleration & Power, looking for ideas... (2 Viewers)

bajaphile

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Apr 6, 2008
Messages
2,145
Location
Solana Beach, CA
Hi guys,
I've been searching all the terms I could think of for the last 2 weeks trying to figure out what I can test or do to remedy my situation. Nothing really stuck out.

2 weeks ago, the truck was running the way it should. Then overnight it seemed, its lost what I would say about 10% power and acceleration. Especially going up hills. Usually, when I was going up a hill, and give it gas, it would downshift and I could hear that whistle in the engine (almost like a turbo) kick in and it would take off up the hill. Now, it just sits in the same gear and struggles.

If I'm on flat ground, it will do the downshift, but not nearly as early as it did in the past. I find myself with the accelerator pedal all the way down to the floor now just to get up to speed on the freeway!!! In fact, I am driving around town with the accelerator pedal to the floor a lot, where I would have never done that prior.

Truck has 181,000 mi and original HG. No CEL.

What I've done so far to try and remedy it:
- Adjusted accelerator cable 2x (to gas pedal) and no change
- Adjusted transmission kickdown cable and no change
- Inspected distributor cap & rotor (changed 10k mi ago)
- Replaced plugs with OEM Toyota (old plugs all looked great)
- Cleaned Toyota OEM air filter (bought brand new 5k ago)
- Cleaned MAF (Bought brand new 5 years ago by PO)

Things I will be doing unless I find out the issue first
- Need to test the TPS (I feel like I've never had one fail, and don't really know the symptoms of a filed unit)
- I have both fuel filters ready to be swapped. I was planning on doing this my next free weekend.
- Possibly rent a fuel pressure kit, as it seems like it is fuel related.
- My accelerator cable is in pretty bad shape, but don't see why it would cause this issue overnight

A few other observations:
- Ultragage is running LOW on temps. City driving showing 176-179F, usually hovers around 179-183F. Hard freeway driving is usually 183-187F, now in the 180-184F range.
- Filled up 2 weeks ago at some random gas station in the mountains, and feel like it might be related. I've run only 1 tank of gas through it after that tank.
- No loss of coolant, or HG related symptoms from what I can tell.
- Just passed smog with flying colors, catalytic converters aren't hot or showing any signs of being clogged.

Anyone else have some advice, or tests to run or check?? I would be grateful. The truck idles smooth and otherwise is fine. Just really a small loss of power which is making it difficult to track since it isn't throwing any codes or any major red flags.
 
Joined
Jan 26, 2017
Messages
993
Location
Chattanooga, Tn
Hi guys,
I've been searching all the terms I could think of for the last 2 weeks trying to figure out what I can test or do to remedy my situation. Nothing really stuck out.

2 weeks ago, the truck was running the way it should. Then overnight it seemed, its lost what I would say about 10% power and acceleration. Especially going up hills. Usually, when I was going up a hill, and give it gas, it would downshift and I could hear that whistle in the engine (almost like a turbo) kick in and it would take off up the hill. Now, it just sits in the same gear and struggles.

If I'm on flat ground, it will do the downshift, but not nearly as early as it did in the past. I find myself with the accelerator pedal all the way down to the floor now just to get up to speed on the freeway!!! In fact, I am driving around town with the accelerator pedal to the floor a lot, where I would have never done that prior.

Truck has 181,000 mi and original HG. No CEL.

What I've done so far to try and remedy it:
- Adjusted accelerator cable 2x (to gas pedal) and no change
- Adjusted transmission kickdown cable and no change
- Inspected distributor cap & rotor (changed 10k mi ago)
- Replaced plugs with OEM Toyota (old plugs all looked great)
- Cleaned Toyota OEM air filter (bought brand new 5k ago)
- Cleaned MAF (Bought brand new 5 years ago by PO)

Things I will be doing unless I find out the issue first
- Need to test the TPS (I feel like I've never had one fail, and don't really know the symptoms of a filed unit)
- I have both fuel filters ready to be swapped. I was planning on doing this my next free weekend.
- Possibly rent a fuel pressure kit, as it seems like it is fuel related.
- My accelerator cable is in pretty bad shape, but don't see why it would cause this issue overnight

A few other observations:
- Ultragage is running LOW on temps. City driving showing 176-179F, usually hovers around 179-183F. Hard freeway driving is usually 183-187F, now in the 180-184F range.
- Filled up 2 weeks ago at some random gas station in the mountains, and feel like it might be related. I've run only 1 tank of gas through it after that tank.
- No loss of coolant, or HG related symptoms from what I can tell.
- Just passed smog with flying colors, catalytic converters aren't hot or showing any signs of being clogged.

Anyone else have some advice, or tests to run or check?? I would be grateful. The truck idles smooth and otherwise is fine. Just really a small loss of power which is making it difficult to track since it isn't throwing any codes or any major red flags.
Did you find a solution the problem? Having thehel same symptoms. Drove the truck home Saturday night and Sunday afternoon was struggling to make it up my hill
 

bajaphile

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Joined
Apr 6, 2008
Messages
2,145
Location
Solana Beach, CA
Well it slowly got better, and I think it was actually just from a bad tank of gas I got. I pulled the negative terminal as well and it helped... Sorry it wasn't something more tangible.
 

RJH

Joined
Mar 19, 2020
Messages
40
Location
Oklahoma City Area
I know this is from 2017... but I am having the same problems after I opened up a few things to try to clean my throttle body to clear a P0401 code.

I recently bought fuel at a rather sketchy place, so it could very well be that, but was wondering if there is anything that could have caused this when checking my throttle body. I only got as far as taking the air filter hose off of the TB and saw that everything was very clean and I didn't want to go any further since I didn't have any spare vacuum hose to replace all of the ones that I would probably break as I took them off.

I'd appreciate any help or suggestions on things to check. My best guess would be adjusting the cables, but I can't figure out what is right or wrong when adjusting the cables. I've tried more slack in the cables and I've tried tightening it up, no luck. Prior to me getting my hands on the thing, it ran great. I drove it 600 miles with no issues.

EDIT:

Turns out I broke a tab on one of the sensors that plug into the TB and it didn't click into place. Plugged back in with the help of a zip tie, adjusted the throttle cable based on FSM, and it is better than before. Now I just need to dive in and try to fix the P0401 during this time of quarantine...
 
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