156 misfire problems

[correlejco]

Just bought a 1998 156 2.0 TS as a non-runner and have spent the weekend fiddling - it now goes like the clappers on the open road - I love it!

However, it won't idle properly, and stalls when I dip the clutch. Idle speed hunts between 200 / 2000 rpm when cold, and settles down to 300 /500 when hot. Revs don't pick up at all when it's cold.

I've been told it may be the air flow sensor but I'd like another opinion before I fork out 150 squids on one. Or maybe an AR dealer can diagnose it? (and the diagnosis would cost £150?).

Any help appreciated. I'm itching to get the car going. More fun than a barrel of monkeys as they say in the song !

John

[pwig]

Well we would charge you anywhere between £40-£80 to tell you whats wrong, just depends how quick we find the problem.

If you then decide to get the work done with us, we knock that investigation fee off.

Thats the way we work anyway

[rustybin]

Before paying a professional I would have a look at the more obvious, such as leaks in the air system (the flexible hose between air flow sensor and air box is a common weak point), fuel supply could also be a culprit along with the idle control valve.

[Wombat Rick]

Mass Airflow Meter (MAF).
It's a very sensitive device which often fails under perfect conditions. Bosch part about £140'ish. It does not show up on diagnostics or light your engine management light.
BUT!
What you can do is unplug it and it will return to a default safe setting. Follow the trunking back from the air box towards the bulkhead. You will see a connector sticking vertically up/down. Unplug it. If the engine drives better with it unplugged, then it's jiggered.

[pdV6]

rustybin said:

idle control valve.

Quite common on the TS engine, I hear.

Easy way to check the MAF is to simply unplug it. If the car runs ok without and isn't happy with, then its probably kaput.

{edit:} Er, like Rick said! must learn to type faster...

>> Edited by pdV6 on Tuesday 19th October 10:24

[lanciachris]

First question has to be what did you do to make it run?

[Alfa Mad]

My thinking is slightly different. Firstly, I'd check the HT leads and the spark plugs. Ensure there is no pitting ot tracking of the spark plugs or their HT leads. Also ensure that no oil leak allow engine oil out of the Cam cover gasket and into the recesses of the spark plugs. It may even be water gathered in the spark plug holes. The 16V Alfa engines appear to collect water there very efficiently. Failing that, I'd check the idle control valve, and free it off and lubricate it as necessary. Don't forget to clean out any choked breather hoses, but I don't think that is the cause.

[correlejco]

Thanks to everyone for their advice. In the end, it was the throttle servo motor suffering from friction and stiction. Cleaning it out with WD-40 and checking and de-griming all the linkages cured the problem (almost). The engine speed still hunts slightly, but it doesn't stall.

The car still occasionally does something of a 'kangaroo' job at low speed in low gears. This may be the same cause as the unstable idling, so I'll have another go at cleaning and lubricating everything.

Thank you all again.

[eddymann]

if you are local to rayners lane ha27he ...pop car in to test
my new alfa examiner out.we dont charge to fault find
if we get the job to fix or sell the part.try cleaning the air flow meter,make sure your air box filter is sealed properly,a bit of dirt will upset the temp wire.
spray a lub.over inlet air pipes,see if car revs the same.
take off cam box top cover and ck.out your coils,plug wires,clean plugs.make sure cam box not leaking oil on to coils+wires.always copperslip plug threads...dont overtight the plugs,they do crack up.
good luck eddythealfaman