156 V6 lumpy at low revs

[logoman]

over the last 2 days my V6 has become progressively more lumpy at low revs and idle. Thought the revs are consistent (ie. the needle is not flicking), the power has gone.
Everything seems fine over 3000; the cars well due for a good service, which it will get next week, I can't tell if its missing by listening to it, and none of the warning lights have come on. The temperature seems a little lower than usual. but what could be the problem?

[wadgebeast]

AFM or AMM? There's a sensor that plugs in next to the air filter that reports back to the ECU. Try unplugging that and see if it runs better. If so, it's a cheap (and common) fix.

[Wombat Rick]

logoman said:

the power has gone.

As mentioned above it does sounds like the air flow meter. Very common fault - German made part you see!

[exgtt]

Hi, the most common symptom for a faulty MAF (airflow meter) is a reluctance to pull above 5k. Lumpy below 3k sounds like spark plugs to me or the Lamda Sensor(the ECU takes data from the Lamda sensor in the exhaust below 5k or three quarter throttle, so the MAF isn't really used below 3k, data is taken from the MAF at above 3/4 throttle or 5k revs) I'd be tempted to service the car first as this cured my lumpyness below 3k (year 2000 156 v6) and then get the Lambda tested.

Ps if its running cooler than 85 degrees get the thermostat changed as it sounds to be stuck open which also won't help in smooth running. Cheap fix this and very common, glad it stick open and not shut though, well done Alfa! : - )

Edited by exgtt on Friday 26th October 15:59

Edited by exgtt on Friday 26th October 16:17