RPM will not go above 2300 (1 Viewer)

[Bodda]

Last weekend, I went to the sand dunes with the local off-roading club here. Unfortunately, I couldn't even make it up the first dune. The leader of the group drove my tuck to see what was wrong with it, and he said it should have much more power, and that my RPMs don't go above ~2300 even when the accelerator is fully depressed.

Engaging the ECT (PWR) button doesn't do much to fix the problem.

Any ideas?
Your help is greatly appreciated!

 

[Locked79]

What vehicle?
What engine?
What transmission?
Gas or diesel?
We need way more info in order to be able to help you.

 

[Bodda]

What vehicle?
What engine?
What transmission?
Gas or diesel?
We need way more info in order to be able to help you.

Hey, thanks for the reply. I totally missed the most important part lol.

Anyway it's a '94 FZJ80, fuel injection, automatic.

 

[theish]

Hey I just had this problem after I pressure washed my engine bay. Water in the electrical connectors(duh) for TPS, the distributor, and the MAF. I would make sure nothing is wrong with those connections then take a look at the sensors/distributor itself. Its probably one of the three. Once I let all the water dry out it ran perfect. Maybe not the same cause but for sure those three can cause the RPM limit problem.

 

[Timpanogos Slim]

Check engine light? Pull codes?

in a 94 you will have to put a paperclip into the right contacts in the diagnostic header under the hood and count the blinks of the CEL. search for obd1 codes here in this forum.

 

[flintknapper]

Check to see that your catalytic converter(s) are not clogged.

 

[Bodda]

Some extra information: I can push the RPMs all the way to the end while the car is in P or N. In D, it will stop right at the 2000 RPM mark and stay there, until it changes gears a coupe of times, then it might go a little higher to about 2300 RPM.

Any other ideas as to what this could be?

 

[Bardiya]

Some extra information: I can push the RPMs all the way to the end while the car is in P or N. In D, it will stop right at the 2000 RPM mark and stay there, until it changes gears a coupe of times, then it might go a little higher to about 2300 RPM.

Any other ideas as to what this could be?

Torque Converter?

 

[Dave 2000]

This is not something simple like the throttle cable 'outer' has slipped so you are not getting full throttle? Having max rpm in neutral/park is not indicative of FSD at the engine butterfly.

regards

Dave

 

[Willopat]

check the mass air flow wiring connector. get someone to push on it and move the wiring around with it running and you giving it lots of gas.

 

[inkpot]

Check engine light? Pull codes?

in a 94 you will have to put a paperclip into the right contacts in the diagnostic header under the hood and count the blinks of the CEL. search for obd1 codes here in this forum.

 

[elhombre]

Just throwing it out there and haven't heard of it before, but could the fuel pump relay be stuck on low power and not able to shift to high voltage? Just don't know if the low side will give enough fuel for the engine to rev up high with no load, but starve the engine of fuel under load.

I believe you can use a jumper wire at the under hood computer port and give full 12 volts to the pump and bypass the relay. But I have never tried it and maybe giving you a bunch of erroneous crap. Don't know what pin would need to be used either. But if you can bypass the relay that way, drive it around and see if that gets your engine screaming for mercy again.

 

[Timpanogos Slim]

Just throwing it out there and haven't heard of it before, but could the fuel pump relay be stuck on low power and not able to shift to high voltage? Just don't know if the low side will give enough fuel for the engine to rev up high with no load, but starve the engine of fuel under load.
.

Is that even a thing? I was under the impression that like most non-race gas engines with port (or throttle body) injection, the fuel pump delivers a constant flow that is enough for WOT, and the pressure regulator at the rail just returns the unused fuel to the tank.

Pretty sure the fuel pump relay has just the one pole.

Some more recent systems, particularly with direct injection, have PWM controlled in-tank fuel pumps that supply on the order of 100psi to a high pressure fuel pump on the head, which supplies on the order of 350psi to the injectors.

 

[Timpanogos Slim]

Oh, i see now, the fuel pump in this truck is usually run through a resistor, and the relay bypasses the resistor for full pressure.

You should really download the PDF version of the factory service manual. Search for it.