I've been ignoring the problem for a while hoping it would go away. Symptoms are;
Hunting slightly at idle
Feels like its lost power at low revs sometimes, then as if by magic it cures itself and theres a noticeable pickup almost like an injector hasn't been fueling properly then clears itself.
I think it could be;
Fuel Pressure regulator
Idle control Valve
Air Mass meter
Air temp sender
Is it hunting for petrol or overfueling at idle ???
Not sure what the symptoms are (speak to Mr T on AO) but, apparently the MAF sensors are very fragile on the 16v and actually break
Mr T has went through 3 in about 6 months. Something to do with electrical spiking of the voltage and blah blah (he kinda lost me after that ) and the dingle dangle "blows" as a result of too high a voltage. He is gonna fit a voltage regulator of some sort to his 156 to prevent it happening again.
Our 145 had a new MAF (£140) a few months ago. It was not itself for a while and then it wouldn't pull the skin off a rice pud so it was pretty obviously grim. The crank sensor (£30) is now dicky and that has shown itself by not starting everytime when hot...
Our lambda sensor (£75) has died completely and the car is running in a safe, but lacklustre mode.
All prices are + VAT and fitting and funnily enough are all made by Bosch!
The temp sender switch does fail but is a cheap fix (£10-£20 depending on year) so you could bung one of those on as a start...
My money would be on the MAF and then the lambda sensor I'm afraid.
I would try the temp sender first located in the top of the thermostat on 16v models they only cost about 10 quid and easy to change. This sender control the AFM commensurate with the engine coolant temp I think
From experience of over a year of bad running on my 1.8 16V, coil packs - they split open and short down, when cold and also when the engine loads up, and recently traced a fault on the fuel system to a split fuel pick up pipe inside the tank - this gave alsorts of bad running and then would suddenly clear, somedays the car was perfect others it was a complete dog.