Hi I have problem with my 944s (ventiler), when I do a lot of round town driving stop start, it struggles sometimes to tick over and cuts out quite a bit when I stop, please can anyone tell me the obvious items I need to look at first, either clean, replace etc, it's also lumpy tick over when first started in the morning, I use it daily.
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Cutting out problem
- Thread starter Lance
- Start date
George Elliott
New member
Lance,
there are many possibilities, but I would suggest basics such as:
Plugs
rotor arm
Dizzy Cap
Plug Leads
are checked and are god.
then ISV if a ventiller has one, which I would expect it has
The ISV does a different job on cold running due to fuelling and timing differences, and in a way its an easier job, but if its not behaving it will cause cutting out.
FYI, the ISV (idle stabilisation valve) opens and closes a valve which supplies air to the engine. This is in response to various sources / sensors. It is a random operation. You can imagine the rest
Good luck
George
there are many possibilities, but I would suggest basics such as:
Plugs
rotor arm
Dizzy Cap
Plug Leads
are checked and are god.
then ISV if a ventiller has one, which I would expect it has
The ISV does a different job on cold running due to fuelling and timing differences, and in a way its an easier job, but if its not behaving it will cause cutting out.
FYI, the ISV (idle stabilisation valve) opens and closes a valve which supplies air to the engine. This is in response to various sources / sensors. It is a random operation. You can imagine the rest
Good luck
George
George Elliott
New member
I will check and reply shortly Lance
George Elliott
New member
Lance, I have had a look on the Parts PET and the is an ISV, or as they call it an idle actuator.
I looked on the Workshop Manual, and it shows an Idle Actuator too.
Pls Note, this is just me who has never had a 16v 944 trying to assist, there are others who know the M44/40 engine much better than me and I am happy to be corrected by them. - M44/40....that is the correct engine....?
The WSM shows the ISV located on a run of Black rubber hose, which starts after the AFM but before the throttle body, (look for a 20mm Dia black rubber hose, routed to a die cast aluminium device (the ISV) which is about the size of a Torch Battery Size D, and coming off the opposite side of same, another 20mm Dia black rubber hose which enters the inlet manifold. The hoses will be about 10inches long with moulded in bends. The battery like device will have an electrical connector with 2 wires coming out of the top of it.)
These wires supply a 5v signal which swaps +/- to open and close the valve. If the valve does not respond immediately the ECU struggles to maintain 850rpm tick over.
You can check if its working by disconnecting the 2 wire connection plug while the engine is not running and then restart and see if it behaves the same.
You can also check the ISV Unit by replacing it with a stub of pipe, and observing the ISV operate in your hand as the engine ECU opens and closes it. You may need to clamp off the hose to force a change of condition, I would resist the temptation to disconnect the ISV Plug when its energised. I would perhaps suggest a dose of Carb cleaner into the unit while its out like this.
The ISV function is simply to provide a bypass to the Throttle to feed the engine on tick over.
Hope this is helpful.
I had similar symptoms on a turbo, and the ISV fixed it, but turbos are female and play up for daft reasons [8|]
Good luck
George
I looked on the Workshop Manual, and it shows an Idle Actuator too.
Pls Note, this is just me who has never had a 16v 944 trying to assist, there are others who know the M44/40 engine much better than me and I am happy to be corrected by them. - M44/40....that is the correct engine....?
The WSM shows the ISV located on a run of Black rubber hose, which starts after the AFM but before the throttle body, (look for a 20mm Dia black rubber hose, routed to a die cast aluminium device (the ISV) which is about the size of a Torch Battery Size D, and coming off the opposite side of same, another 20mm Dia black rubber hose which enters the inlet manifold. The hoses will be about 10inches long with moulded in bends. The battery like device will have an electrical connector with 2 wires coming out of the top of it.)
These wires supply a 5v signal which swaps +/- to open and close the valve. If the valve does not respond immediately the ECU struggles to maintain 850rpm tick over.
You can check if its working by disconnecting the 2 wire connection plug while the engine is not running and then restart and see if it behaves the same.
You can also check the ISV Unit by replacing it with a stub of pipe, and observing the ISV operate in your hand as the engine ECU opens and closes it. You may need to clamp off the hose to force a change of condition, I would resist the temptation to disconnect the ISV Plug when its energised. I would perhaps suggest a dose of Carb cleaner into the unit while its out like this.
The ISV function is simply to provide a bypass to the Throttle to feed the engine on tick over.
Hope this is helpful.
I had similar symptoms on a turbo, and the ISV fixed it, but turbos are female and play up for daft reasons [8|]
Good luck
George
Mr.FixitNorm
New member
The ISV or ICV ( idle control valve ) is unfortunately tucked away UNDERNEATH the inlet manifold , almost impossible to get too[8|] why Porsche had to hide something that important which could have, with a bit more thought been made easily accessible is a mystery. I had a few idle issues with my ventiler when I had it, I changed the dizzy cap & rotor arm plus the plugs, but it returned. I then cleaned and adjusted the AFM ( air flow meter ) which isn't for the faint hearted - Clarkes Garage has a good article on it.
The stalling disappeared then for quite a while but after selling her to Hallsey on here I believe it has still done it occasionally so possibly the ICV needs stripping and cleaning ( I believe replacement is expensive )
I was told the inlet manifold needs to come off to do the job easily ! but it might be possible with it in place.
Norm
The stalling disappeared then for quite a while but after selling her to Hallsey on here I believe it has still done it occasionally so possibly the ICV needs stripping and cleaning ( I believe replacement is expensive )
I was told the inlet manifold needs to come off to do the job easily ! but it might be possible with it in place.
Norm
George Elliott
New member
The comments Norm makes re the AFM may be easier to try first, they are literally a wearing part. Easier to test with an Ohm meter and see how consistent the voltage at idle, and how linear the resistance is over the wiper.
Have to say, a spare AFM is a useful item for fault finding (if you accept it is unlikely to have an identical fault)
I got my turbo ISV/ICV out without removing the intake, but had hoped a 16v may not be so awkward.
Have to say, a spare AFM is a useful item for fault finding (if you accept it is unlikely to have an identical fault)
I got my turbo ISV/ICV out without removing the intake, but had hoped a 16v may not be so awkward.
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