Hard to diagnose - chk engine light (2 Viewers)

[samuelfzj105]

Hi everybody,

I have an fzj105 series, auto, petrol 1fz-fe.

Issue Im having is an odd one and somewhat hard to diagnose exactly what is causing it, Im looking for any advice possible at this point.

if the engine is cold I have to sit and let it warm up to at least a quarter on the temp gauge. OR if I just start driving the vehicle will begin to warm up but once it hits a quarter on the temp gauge it will bog down throw a chk engine light and put itself in limp mode. This doesn’t happen if I sit and let it warm up without driving it.

The code it’s throwing is a knock sensor 1 & 2. I have had this in my mechanics numerous times now and he can’t put his finger on what the heck is happening. They have tested the knock sensors and they are healthy, also have replaced the knock sensor loom to the ECU.

The engine/vehicle is otherwise in very good shape. I’ve spent $ thousands on restoring it to its a1 factory glory aside from this one issue with the chk engine code throwing, Iimp mode.

Any advice would be appreciated, it’s quite the odd issue indeed.

Cheers,
Sam

 

[samuelfzj105]

Bump

 

[x8o8drifter]

IMO Techstream if your mechanic isn't already doing that. (Or at least something that can read engine stuff in real time, like fuel trims/MAF voltages/etc)
It might point to what is causing it.
I had a random misfire throw a code and using Techstream we figured out it only happened at startup/crank and it happened on all cylinders.
We had just changed out the WP/Timing belt and it jogged my friend memory that he may have forgotten to torque the crank bolt down. (Timing wheel was wobbling)

It's not expensive either.

 

[samuelfzj105]

IMO Techstream if your mechanic isn't already doing that. (Or at least something that can read engine stuff in real time, like fuel trims/MAF voltages/etc)
It might point to what is causing it.
I had a random misfire throw a code and using Techstream we figured out it only happened at startup/crank and it happened on all cylinders.
We had just changed out the WP/Timing belt and it jogged my friend memory that he may have forgotten to torque the crank bolt down. (Timing wheel was wobbling)

It's not expensive either.

Thanks for your input, I will ask my mechanic regarding Techstream. Anything is worth a shot at this point, have been trying to get to the bottom of it for over 12 months. Cheers

 

[Mike NXP]

I don't know as much about the 1FZ so can't speak to any relevant experience.. Most of us have the 2UZ...... ..I know throwing parts at the problem isn't always ideal but how much do new knock sensors cost? I know they tested good but IDK, are they easy to get to and swap out with OEM part?

Does your engine have MAF sensor ?

I'm trying to think of what else could cause an engine to run bad when cold but then OK when warmed up.....CEL says knock sensors , hmmm


Random relevant thread that may have some info, different engine but IDK maybe some ideas..There is talk of fuel injectors or maybe plugs being the culprit but eventually he replaced knock sensor ( again ) to fix the problem......I don't see how a fuel injector would perform different when cold then hot but maybe

Thread 'Knock sensor issue'

Dec 23, 2019

Gday all
Where having issues with my son's 1993 FZJ80R .
It's throwing a check engine light , diagnostic is showing code 55 which is knock sensor .
This is driving us mental.
We have tried new knock sensors , different ECM and re wiring
We've had no luck , please help

• alaw
• Replies: 52
• Forum: 80-Series Tech

 

[89BIGBLUE]

Is there a temp sensor somewhere, that feeds temp data to the fuel system?

 

[Malleus]

How are they "testing" a knock sensor? Attaching it to a shake weight?