ls1 flat spot

[Drift_R32]

Hey all

Strange issue
My ls1 wont rev past 4500 exactly

It revs up to it fine
But then its like hitting a flat spot and it has nothing

Has cam,tune,full exhaust


It has revved hard to limiter fine before
But now it wont

Ideas?? Cheers

[KAL SPL]

Cats collapsed ?

[Drift_R32]

Possible has stock cats still which is shit
But i doubt it would be exactly 4500rpm every time :/

Its like a sensor gets the wrong reading and stops all power

[Drift_R32]

Ill check cats though

[H1GHROLLR]

This is one for Ricey :)

[Tre-Cool]

blocked cat

[Drift_R32]

Blocked cats would be noisy though
Ive had them before and they clatter etc once they break apart


Also it reved to limiter this morning in 1st

Then later it wouldnt in 3rd and 4th

[Sfidz]

bash cat out

[Drift_R32]

bash cat out

Not that simple
Theres 500mm of curved pipe either side lol

[Tre-Cool]

Blocked cats would be noisy though
Ive had them before and they clatter etc once they break apart


Also it reved to limiter this morning in 1st

Then later it wouldnt in 3rd and 4th

not really the same amount of fuel/air in 1st gear as the load is not there.

been there done that a long time ago. smash it out.

i've had a cat that turned on itself blocking air, it didnt make a sound.

[Drift_R32]

Alright will give it a go

Cheers guys

[ED40]

I had a similar problem with another engine, replaced heaps of shit only to find later on when I upgraded valve springs it went away. Maybe you need a new set of springs... I'd disconnect the exhaust and see if that fixes it first.

[Drift_R32]

Has upgraded springs about 15xxxkm old if that helps

[31-EVO]

Fuel pump, valve springs are possible if the rocker arm is loose and it isn't sitting properly, but it sure sounds like a pump/MRA issue, I don't know how many I've replaced

[ReaperSS]

Could be a tps sensor not allowing it to go past a certin point. If its that you cant buy sensor by itself. part of throttle body

[Drift_R32]

hmm will get it looked at tues and see what comes up

[RICEY]

I think his is pre VZ so no electronic throttle, if TPS fails it would be throwing engine lights and doing weird shit.

Drop the cats off and rev it up, that will either eliminate them or identify them as the issue. Will sound mint too :D

If you can get hold of a fuel pressure gauge you can screw it onto the rail at the valve and check pressures.

Any engine lights ?

[Drift_R32]

will do both this arvo at the workshop

umm yeh one code but i havnt put it on the scan tool yet
but wasnt pulling any codes before and was still doing it

since i got car it feels pretty weak

has large cam, exhaust, otr, 4:11s and manual but still feels like it is lacking alot

something is definately stoping power been made.

it APPARENTLY was tuned by mitch so i doubt its tune

i also know 02 sensors are prob in need of changing too
but doubt they would cause the revving issue.

[ReaperSS]

May also be idle air?

[Turbo2.6L]

Take it to Mitch

[Drift_R32]

yeh asoon as i get a chance

hes unfortunately waaaaay down south now..
will try this saturday.

[RICEY]

Let me know what the code is, will give us a clue.

My scan tool only does VZ onwards...

O2 sensors wont stop it revving youre right.

[indecline]

has it still got stock headers and cats or just stock cats?modded in?

[Drift_R32]

Ok

Code is knock sensor malfunction
And it retarding the timing when it activates

Weird thing it after cleared it brings up code whenever
Driving easy not revving over 2k doing maybe 50kmph kicked code on

[Drift_R32]

Still suspect on fuel pump, maybe new fuel filter is fucked

Possible faulty knock sensor making it go into limp mode

Havnt checked cats im moving away from that
Im pretty sure its not reving pasr 4500 cause its in limp mode

[RICEY]

Dead knock sensor can cause loss of power/ hesitation.

[Drift_R32]

yeh might go ahead and change it just to be safe
its in a pingpingpingping of a spot though under the inlet manifold

[RICEY]

They arent too bad to get off, give me your VIN and Ill price you a sensor up.

[31-EVO]

I have only EVER seen a knock sensor cause issues on a VE 6L, never in my life have I seen one fail on a VZ, not to say that it hasn't however.
If you can get someone to screw a fuel pressure gauge onto the car, and tape the gauge to the windscreen, give it a sack full down the street and see if fuel pressure is dropping off.

[Tre-Cool]

disconnect the knock sensor plug, you'll probably find if your getting knock sensor errors it's actually the wiring harness with a fault.

[ReaperSS]

LS1 Knock sensor part number 12589867.
We sell around 3-4 a month.
Just took a look at ls2 l76 l98 part number 12623730 and sell just as many.


Ls1 Knock sensor is around $70.60+

[RICEY]

disconnect the knock sensor plug, you'll probably find if your getting knock sensor errors it's actually the wiring harness with a fault.

Corrosion, or the sensor isn't bolted down tight enough.

[Drift_R32]

two new sensors and wiring in
old ones where rusty as fuk so heres to hoping

also looked at tune
closed loop turned off
all knock tables turned off ffs

off to mitch

[ASSASIN]

Def not tuned by mitch if that is turned off.

[Drift_R32]

exactly what i was thinking..

[Chompy]

what was the result of this?