anyone know about cats?
Discussion
Hi, just wondered if anyone knew the answer to a technical problem.My friends Honda V6 legend(96) has an idle when cold that is considerably faster than it should be.It takes an eternity to go down when the vehicle is warmed up, but never really goes to its correct level.Its always slightly high!I have now noticed the cats has been removed and the sensors are doing nothing.....well they should be doing something?I'm guessing this is the problem?Any thoughts would be thankfully received,cheers
How do you know the sensors are doing nothing ?? Have you tested them ??
You also say plural, so more than one ?? So both are doing nothing ?? Are they both faulty ?
If its a fast idle, chances are its an air leak in the inlet tract somewhere.
I doubt either removing cats, or faulty lambda sensors would cause it.
Test the sensors, or even un-plug them and see if it makes a difference.
You also say plural, so more than one ?? So both are doing nothing ?? Are they both faulty ?
If its a fast idle, chances are its an air leak in the inlet tract somewhere.
I doubt either removing cats, or faulty lambda sensors would cause it.
Test the sensors, or even un-plug them and see if it makes a difference.
Could this be a sign that the ECU has detected a fault and switched to 'limp home' mode (if it has such a thing)? For example if the cat removal has thrown the fuel map far enough out, it could be under/overfuelling further than the ECU is able to correct in closed loop mode prompting the ECU to assume that the lambda sensors have both failed. Or perhaps they have been poisoned or sooted up and actually have failed. Probably time to look at the ECU diagnostics to see what it reckons is happening.
Hi, thanks for your replies.When i said the sensors are doing nothing they are quite simply not plugged in as the place they should be has been removed(i'll double check theres nothing else just floating around)Bare with me as i havn't messed around with this, just trying to help.There does not appear to be any ecu fault,or at least the diagnostics at the honda dealership say so!
Its not running rich, all within what would be normal and there is no excessive soot or smoke.....or any smoke to be accurate.Its just got a higher than normal idle,which makes it a sod to drive(like its cold all the time)but with it been autobox makes gear selection clunky....like the chokes on.To the extent that the engine mount has failed(guessing)because of the slight lurch between gears and engaging drive.
It does seem to get less the hotter the vehicle gets but it never idles at its correct level.
I bet its doing the brake pads no good as you have to hover on the pedal to maintain 30mph
I will go check the vehicle so as to be more accurate as to what is missing...and check its not drawing in air from somewhere else.
thanks again.
>> Edited by pawsmcgraw on Saturday 19th March 00:25
Its not running rich, all within what would be normal and there is no excessive soot or smoke.....or any smoke to be accurate.Its just got a higher than normal idle,which makes it a sod to drive(like its cold all the time)but with it been autobox makes gear selection clunky....like the chokes on.To the extent that the engine mount has failed(guessing)because of the slight lurch between gears and engaging drive.
It does seem to get less the hotter the vehicle gets but it never idles at its correct level.
I bet its doing the brake pads no good as you have to hover on the pedal to maintain 30mph
I will go check the vehicle so as to be more accurate as to what is missing...and check its not drawing in air from somewhere else.
thanks again.
>> Edited by pawsmcgraw on Saturday 19th March 00:25
Weld 2 M18x1.5 bungs into the exhaust and screw the lambda sensors back in.
Why anyone would remove them is beyond me. But worst case for the sensors the way you ahve them now, is that it will use loads of fuel. It shouldnt affect general driving that much really.
Id still say the high idle is due to too much air getting in.
Air leak
Faulty ISCV
Has someone opened the throttle ?? generally speaking most modern efi systems run a fully closed throttle at idle, with the ISCV allowing any air needed to idel.
Why anyone would remove them is beyond me. But worst case for the sensors the way you ahve them now, is that it will use loads of fuel. It shouldnt affect general driving that much really.
Id still say the high idle is due to too much air getting in.
Air leak
Faulty ISCV
Has someone opened the throttle ?? generally speaking most modern efi systems run a fully closed throttle at idle, with the ISCV allowing any air needed to idel.
you say the cats removed. and the CO2 sensors are floating around
the sensors must be fitted into the down pipes or how can the ECU box adjust the mixture correctly, that is if its a closed loop system, if its a open loop system you can adjust the mixture seperate to the CO2 operationing. also check the fault code from the ECU flash codes that will give you a clue to what going on
the sensors must be fitted into the down pipes or how can the ECU box adjust the mixture correctly, that is if its a closed loop system, if its a open loop system you can adjust the mixture seperate to the CO2 operationing. also check the fault code from the ECU flash codes that will give you a clue to what going on
seriously impressed by the general lack of understanding here about engine control systems!
it's hard to diagnose these things remotely, but here are a few pointers:
- check your throttle position sensor / switch is triggering a closed-throttle signal to the ECU.
- check to see if the idle bypass valve is doing anything (by disconnecting it and looking for a change in engine speed)
- check if you can reduce the engine speed by hand by choking off the idle bypass flow (if you can - depends on how it's plumbed in)
- don't worry about the HO2S/oxygen sensors for the moment. They'd be handy, but they're not important for solving this problem.
- check the function of the coolant temperature sensor. they tend to fail 'cold' so could lead to an elevated target idle speed
That should be enough work for a bit...
A
it's hard to diagnose these things remotely, but here are a few pointers:
- check your throttle position sensor / switch is triggering a closed-throttle signal to the ECU.
- check to see if the idle bypass valve is doing anything (by disconnecting it and looking for a change in engine speed)
- check if you can reduce the engine speed by hand by choking off the idle bypass flow (if you can - depends on how it's plumbed in)
- don't worry about the HO2S/oxygen sensors for the moment. They'd be handy, but they're not important for solving this problem.
- check the function of the coolant temperature sensor. they tend to fail 'cold' so could lead to an elevated target idle speed
That should be enough work for a bit...
A
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff