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80 Series Check engine light

yeppoonmike

New Member
Joined
Dec 8, 2022
Messages
4
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australia
Hi All
I have a 40th anniversary 80 series 1FZ-FE. I recently had the head done, new valves and seats with everything else. i also replaced the front knock sensor, front water.
temp sensor and throttle sensor. it runs like a dream until the check engine light comes on and it goes into limp mode. i have done the paper clip test and it shows no faults.
is there any method to stop the check engine light from coming on
cheers

Mike

I have replaced both knock sensors (front and Rear) still no change,
From a cold start it runs normal until operating temp is reached then it slips into limp mode and the check engine light comes on.
I have replaced the thermostat, but no difference, could the temp sensor be the problem.
Any help would be appreciated
cheers
Mike
 
Last edited:
Your statements, 'the paper clip test' and 'limp mode', don't go together in my mind.
Is the AU 40th OBD1??
Need a code reader otherwise.
 
i have replace the front and rear knock sensors no change.
from a cold start the engine behaves normally, as soon as operating temperature is reached the check engine light comes on and back into limp mode.
i replaced the thermostat ( just in case) but no difference so maybe the water temp sensor ?
any ideas would be appreciated. i ordered a new one
Mike
 
Have you checked the rubber air inlet hose from the air filter for splits?
 
haven't checked the rubber air inlet hose but will do.
Engine timing is set at 3deg before tdc
 
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Did this start immediately after the head work? If so, take it back to the mech and have them check it out.
May be pinched/damaged wiring in the engine harness. What condition is that in? Specifically in and around where it comes off the firewall and runs down into the engine.
 
Have you let the engine idle from cold through to warm without touching the throttle? If so, does it run smooth and then the idle starts to get rough as the engine warms and then the check engine light comes on? If so it could be a sticking valve, new or not I have seen it happen. It's because a cold idle (read rich) is ignored by the sensors in the exhaust until the engine reaches a certain temperature, once warm the mixture weakens and then this is picked up by the sensor as incomplete combustion is occurring in one of the cylinders.


Regards

Dave
 
Just to let you know the engine runs like a dream, i have let it idle up to operating temp and it still runs as smooth as.
so, i take it for a run and all is well. for about 1Klm then the check engine light comes on and it goes into limp mode.
I have stopped. sat for 5 minutes Started it, no engine light then drive for the same distance and the same thing happens
 
Sensor? Get a can of plumbers pipe freeze, next time it plays up give just one sensor a squirt and see if the problem disappears. It's what I use to find sensors that fail when warm, normal culprit is the crank angle sensor.

Regards

Dave.
 
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