Hi all

I'm new to this so please bear with me.

I imagine this has been covered extensively but nonetheless I'd appreciate some quick and hopefully definitive answers if there are any.

The car is a 2007 1.8 petrol manual that has covered 72K. I bought it cheap a few years ago as it wasn't running properly - most of the issue was cured by replacing the manifold control unit however it never did idle smoothly. With the air intake hose removed from the throttle body the throttle valve can be seen fluctuating at normal idle speed - ie. not at first when started from cold - which presumably suggests an air/vacuum leak. The engine makes a whistling sound at idle which may also support this theory.

This was okay for a while but more recently the fuel and oil consumption have increased, and the revs started to drop to the point of stalling or almost stalling when coming to a stop. The car also had a tendency to hiccup at higher revs when accelerating, particularly noticeable on motorway driving, and this has also now become much worse. 

Having researched this my conclusion was that the PCV valve and/or hose were the most likely causes. I took the car to my local indy yesterday with the instructions to remove the inlet manifold and replace the above whilst also checking the manifold flaps. I suspect that the mechanic just couldn't be bothered as he told me that all he could find wrong was a slight mis-fire which was probably coil packs. I haven't tested these yet or inspected the condition of the plugs (replaced less than 2 years ago although admittedly I didn't check clearances..) but would have thought in light of all the above issues that this is more likely to be a symptom than a cause.

If anyone has any definitive experience of these issues then please let me know. I would politely request not to have a list of possible suggestions as I really don't want to spend ages trying to figure this out if I can possibly avoid it. 

I should add that the throttle body and EGR valve are completely clean, and that weirdly it runs better with the AC switched on, which all but eliminates the revs dropping issue.

Thanks

Max   

Read the voltage from the battery positive to negative

Then read the voltage from the battery positive to the cylinder head as negative

If there is a considerable difference fit an engine earth strap from the cylinder head lifting eye bolt to the body