Charecter1

Okay guys this is my last thread before I take my 1993 4runner 3vze to the shop because I've tried everything to fix its problem.
The problem is that the truck with accelerate just fine when you start it but as soon as the engine gets warmer, anything past 25% of the throttle, the truck will just bog and slow down instead of speeding up. Even full throttle I can't get the thing to get over 30. It takes a few minutes for the the power to finally show up and before it does you can hear it backfire and struggle.
I have no check engine light and its an automatic transmission.
All fluids are good and transmission is fine.
Things I've replaced:
Fuel filter
Wires
Plugs
Cap
Rotor
Plenum gasket
Vacuum lines
Coil
Vafm
Nothing seemed to work. I think its my tps, fuel injectors or my ICM. I did a vacuum, fuel pressure and compression check and all three checked out good so now I'm lost on what it could be. My mechanic doesn't know either.

YoshiMan

I have had a similar issue with mine two times, and once was a bad Throttle Position Sensor, and the second was a vacuum switching valve on the back of the motor where a vacuum hose had snapped off.

I can't think off the top of my head what the particular valve was called, but it was thermostatically controlled, and once the engine heated up and the valve opened, it created a large vacuum leak.

Charecter1

Are you talking about the egr valve?

jason191918

egr was going to be my suggestion. I had a nasty bog and pulling the egr off fixed it.

Charecter1

So you just drove without the egr?

oldmandan

How much pressure is coming out of exhaust? Try dropping the catalytic converter and see if that changes anything."

scope103

Where is the timing set? Mis-set timing will cause those symptoms, and while the tool is $20, verifying timing is so basic I have to think you've already done that. (Don't forget you need the jumper to set base timing.)

PS A thermostatically controlled valve in the back of the engine with a broken nipple is almost certainly the Thermal Vacuum Valve (or Bi-metallic switching valve) that controls the vacuum to the evaporative canister. But the opening is so small I'd be surprised if the performance hit would be so bad as "bogging."

Charecter1

the timing is set at 15 btdc right now because the trucks symptoms are even worse at 10btdc. ive been driving without the cat for 2 days thinking that was the problem and its not. tonight when i went to drive home from work, it was harder to start and sometimes idled really low like at 500rpm. as soon as i even touched the gas it would die or almost die and i couldnt even move the damn thing. i actually had to tow it home.
i let the gas tank get to almost empty to where to light was on and filled it up this morning. it drove to work just fine but as soon as i let it sit for 6 hours, it completely ˟˟˟˟ out. right now its not even drive-able.

Charecter1

also when i checked fuel pressure, i never tried it while in drive with WOT, i only checked the pressure in park at idle.

oldmandan

Have you checked for an intake vacuum leak.Take throttle body off and check tps with feeler gauges to specs and reinstall and try that but you said you have no light right ?If the throttle position sensor was bad,it would set a code.

Charecter1

I already checked for a vacuum leak at the intake and its all clear. Yeah the truck isn't throwing any codes. I know fuel pressure cant be read by the computer so I'm going to check my pump. Right now the truck dies right after I start it so it can't go anywhere.

jason191918

correct. look here:

https://www.yotatech.com/forums/f116...05/index6.html

post 114

Charecter1

Update on the truck, the problem is fixed. I replaced the fuel pump and it fixed it.