When l was travelling yesterday on the motorway, when my Peugeot 306 1.8 automatic (1998) went over 70mph, the engine management light came on (orange light above airbag light with a picture of an engine with a ''K'' in it) and the car went into limp mode (car reduces speed to protect itself), it got so bad the car went to 40mph up a small hill on the M40, l knew if it went below 40 l would have to pull into the hard shoulder.

l phoned my uncle and he said disconnect the battery and wait a couple of minutes then reconnect it, sure enough this worked about 20miles until it went into limp mode again.

When l came off the motorway the car sounded loud at low speeds, when l took off at the traffic lights, the car moved off very slowly then it got a boost of power from somewhere and drove off?? the gear changes are sluggish at lower speeds.

BUT when you disconnect the battery for a minute it goes back to working fine for a little while???

anyone know what might be wrong??? thanks

matbe the transmition is damaged or the auto clutch.

call Peugeot customer services and ask them.

Since disconnecting & re-connecting the battery worked for a while, this says to me that ECU electronic Engine Unit has something to do with it.
l am guessing that after 20 miles of high speed, some engine sensor is not allowing ur engine enough fuel due to temperature or speed sensors. The ECU cuts the fuel or air supply to the injection?
Suddenly ur car got 'a boost of power' because something started working correctly. This will probably worsen, if not dealt with soon.

COINCIDENTLY.while u took 20 minutes to find a spanner, remove, wait, install battery.this could have given something time to ''cool down'' & work better?? Then after 20 miles it heated up again??

If ur car had a manual / clutch, l would say that slow speeds & high engine noise were due to a slipping, worn out cutch disc..but u have an automatic.
Please check ur auto trans fluid level, & does ur gearbox have a ''filter''? Have u ever changed or cleaned it?

l know little about the automatic gearbox, sorry.

A Peugeot dealership ($$$) will connect ur car to the diagnostic computor to test all sensors at various rpm's.

lets get your car to a Peugeot dealer and connect it to a Peugeot Planet System, then you know more if there're stored faults in the memory.