Help please Massive power loss when giving stick

Calling 300zx gurus i have a problem i cant seem to diagnose. The car idles fine, runs fine when driving slow but when you put your foot down it looses all power and goes no where, the motor doesnt drop out like a spark issue its almost like the timing has been ridiculously retarted. Done a error check and all its throwing is "fuel temp circuit" from what iv read this woumd not cause the dramatic loss in power im experiencing the only thing i havent tried is a new afm could that be the issue or does someone have an idea what it could be? Cheers for any advice.

 

Have you checked?

Boost leak or injector connectors are corroded?

 

Yeah, Id be looking at boost/vac leak and fuel delivery. Any idea when the fuel filter was replaced last?

 

:agree:

 

If your coil pack connectors are dodgy the motor can die under acceleration. Check them for corrosion.

 

"Done a error check and all its throwing is "fuel temp circuit" from what iv read this woumd not cause the dramatic loss in power im experiencing the only thing i havent tried is a new afm could that be the issue or does someone have an idea what it could be?"

Fuel Temperature Sensor
The fuel temperature sensor built into the fuel tube senses fuel temperature.
When the fuel temperature is higher than specified, the ECU turns the Pressure Regulator Vacuum Relief Control Solenoid Valve (PRVR) solenoid ON & raises fuel pressure by cutting the vacuum signal.

This is what the ECU is telling you.

What do you think happens when the fuel pressure is raised?

 

OH oh oh pick me Mr Z Pick me!!! *hand in the air*

 

You have the ball.....

.....take it away!

 

*clears throat*
You will start to run richer. When it is too rich you wont get a complete burn of the fuel in the chamber which can lead to plugs foul which will cause them to prevent firing. When the plug fails to fire you may experience what is known as a misfire, this will lead to a power loss.


Seriously, on a side note, if it throws a code i am pretty sure it will retard timing too. Fix the issue, clear the code and go from there.

 

Oh NO!

......you've DROPPED the ball!

I'll admit it was a difficult pass to catch though.

Let's try another catch of the ball?

Why would there be a requirement to increase fuel pressure?
Hint: Tom (Fists) is on the right track.

 

Diagnosing drivability issues begins with collecting evidence & looking for clues.

What we have been told is.
1) The engine is down on power under load.
2) The ECU has logged a fault code relating to fuel temperature, (this should be a code 42).

The EFI system keeps the fuel rail cool by recirculating fuel back to the fuel tank.

If the fuel temperature is high, the ECU will cut vacuum & the fuel pressure will increase to increase the fuel flow.
By increasing the fuel flow more fuel will return to the tank thereby removing heat.

If the fuel filter is restricted, or the fuel pump is on its last legs, then the fuel flow will be reduced & you aren't going to make power without an adequate supply of fuel.

However, the fault code does not mean this is the problem.

The fault code tells us there is a problem with the Fuel Temperature Circuit.

The ECU has registered an abnormally high or low voltage in the Fuel Temperature Sensor Circuit, which would indicate the circuit is open or shorted.

Therefore you need to check the harness & the connector, as well as the Fuel Temperature Sensor.

Because if the circuit is defective the fuel pressure won't increase.

Madcow is correct is saying the code needs to be rectified.
Fists is also correct in saying check the fuel delivery system & that's where I'd start.

At the end of the day it's possible the problem may not be related to the fuel system.
Just sayin.........

 

thread jack:

I am 99% sure both my FPR's vac lined directly to the balance tube...

My zed is running 40psi of fuel pressure constantly and im preety sure its rich as a mofo. It dosn't ping at all on 95 octane fuel when using a Mines chipped ECU... and the mines ECU is MUCH more pleasant to drive than the stock ecu (mainly light throttle response at 1500-2500rpm)

I'm showing code 55

 

Code 55 is what everyone would like to see.
If your engine is running rich as you suspect you should correct the situation.
How would you confirm your suspicion?

 

Awww I misunderstood the question, that will teach me for skim reading!

 

The important thing is that you laced up & had a go.
Despite the fact we weren't on the same page, you were 100% correct in saying the fault code needs to be rectified.

 

Chears for all the info and help guys turned out to be a dodgy s2 ptu i got off someone on facebook. Put my old s1 ptu back on and it went fine, dam facebook parts. Thanks for everyones time and the lessions east coast z lol. P.S cheddel get your own post lol

 

I should correct this. Though with the Mines ECU and 95 octane fuel - I'm not so sure.

I don't have easy access to a wide band. Using one for a few power runs and checking mixtures would be a $100~ exercise - and thats precious funds towards replacement tailshaft and wheels...

My excellent sense of smell, higher than normal fuel pressure, lack of cat converters and aboriginal heritage leads me to believe its running rich.

 

Well first thing to look into is your fuel pressure, double check your vacuum lines to see if the prvr has been disconnected. The fuel pressure reg is on the left (passenger) side of the plenum and should be the only thing that controls fuel pressure. Once youve confirmed the prvr is bypassed see if disconneting the fpr's vac line affects pressure at idle by disconnecting it, you can also apply vacuum and pressure manually with a good set of lungs or a syringe.

 

Wideband's? You don't need those.
Do you have ECU Talk, or something similar?
If not, put the $100 away for one.