Doesn't sound too bad. The cough at start up often indicates the butterfly on the throttle body is either sticking or adjusted incorrectly. Try some throttle body cleaner (not carburetor cleaner) e.g. CRC Throttle Body and Air Intake Cleaner 400g on it and check it has the correct gap when cold. Also check the wiring near the harmonic balancer on both the crank and camshaft sensors is sound and their connector are clean.
"sprayed WD40 between the manifold and the head to make sure there was no leaks and replaced the inlet manifold loom. This won't work usually on a modern computerise fuel injected computer controlled negine. The manifolds typically leak at number 1 and or 6 as the nuts on the manifold retaining studs there loosen over time and the very bottom parts of the gasket then burns out. Because only a small part of the gasket has burnt out, simply re-tightening the nuts won't fix it and you will need to replace the gasket remembering to torque to specification in a circular patter from the center of the manifold outward.
Note they also often leak on the vaccum line that goes to the evap purge tank so check that too. Also double check the PCV valve is properly seated and there is no vac cum leak there or on any of the PCV system hoses and that the little plastic T pieces on the small vaccum under the throttle body is not cracked and leaking.
Note that the old pre-computerised fuel injection trick of using/spraying engine start sprays, WD40, benzene, various gas,es water, oil etc around the manifold will most often not work to find these leaks as the ECU very rapidly adjust for the change in air in the mixture and it's usually impossible to pick up any change in the engine noise or rpms using this old method. As it the lowest point of the gasket that burns out creating the vacuum leak, you are also fighting gravity with any gases or fluid sprayed around just falling to the ground rather than being sucked in where the small piece of gasket has burnt through.
Instead use a length of windscreen washer sized hose with one end in or close to the ear to listen for the no mistaking tell-tale sucking noise of a vacuum leak while poking around under the manifold at idle (with engine both cold and hot as the gap between the head and the manifold changes as the metal in the manifold and head expands and shrinks with heat and cooling).
Alternatively you can successfully use an adapted party fog machine from Altronics or Jaycar (e.g. 400W Mini Fog Machine with RGB LEDs | Jaycar Electronics ) as a smoke machine. leak detector. It is much easier use if you buy one of these pump up adapters https://www.ebay.com.au/itm/20374305...3ABFBM5K3mp4Zg and fit in to the fog machine though. It makes it more effective and easier to use. But although I have one (an adapted party fog machine) and it works well, I have only rarely needed it to find leaks in uncommon places; the length of hose trick works 95% of the time and is quicker, is simpler and easier.
"sprayed WD40 between the manifold and the head to make sure there was no leaks and replaced the inlet manifold loom. This won't work usually on a modern computerise fuel injected computer controlled negine. The manifolds typically leak at number 1 and or 6 as the nuts on the manifold retaining studs there loosen over time and the very bottom parts of the gasket then burns out. Because only a small part of the gasket has burnt out, simply re-tightening the nuts won't fix it and you will need to replace the gasket remembering to torque to specification in a circular patter from the center of the manifold outward.
Note they also often leak on the vaccum line that goes to the evap purge tank so check that too. Also double check the PCV valve is properly seated and there is no vac cum leak there or on any of the PCV system hoses and that the little plastic T pieces on the small vaccum under the throttle body is not cracked and leaking.
Note that the old pre-computerised fuel injection trick of using/spraying engine start sprays, WD40, benzene, various gas,es water, oil etc around the manifold will most often not work to find these leaks as the ECU very rapidly adjust for the change in air in the mixture and it's usually impossible to pick up any change in the engine noise or rpms using this old method. As it the lowest point of the gasket that burns out creating the vacuum leak, you are also fighting gravity with any gases or fluid sprayed around just falling to the ground rather than being sucked in where the small piece of gasket has burnt through.
Instead use a length of windscreen washer sized hose with one end in or close to the ear to listen for the no mistaking tell-tale sucking noise of a vacuum leak while poking around under the manifold at idle (with engine both cold and hot as the gap between the head and the manifold changes as the metal in the manifold and head expands and shrinks with heat and cooling).
Alternatively you can successfully use an adapted party fog machine from Altronics or Jaycar (e.g. 400W Mini Fog Machine with RGB LEDs | Jaycar Electronics ) as a smoke machine. leak detector. It is much easier use if you buy one of these pump up adapters https://www.ebay.com.au/itm/20374305...3ABFBM5K3mp4Zg and fit in to the fog machine though. It makes it more effective and easier to use. But although I have one (an adapted party fog machine) and it works well, I have only rarely needed it to find leaks in uncommon places; the length of hose trick works 95% of the time and is quicker, is simpler and easier.
