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popasmurf

e39 520i surge issue

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hiya,

first off....

Car: E39 520i sedan
Year:1998
Vin number:wbadm22020br55544
Imported from singapore in 1999
Options Auto - steptronic??

love this car! have had it for about 4 months and its been great! had to replace the alternator but as its done 223,000 kms i guess its to be expected.

an issue has arisen with it that is semi difficult to explain but ill try my best...

car starts fine and has no issues with idle etc. BUT when driving once it hits top gear and i am driving at a cruising speed (i.e 50km/h in a 50 k zone or 100 km/h in a 100 k zone) iv'e noticed the engine will on occasion begin to surge. for example when im in a 100 k zone and sitting at 100 k the revs will surge from around 2300-2400 rpm down to 2000-1900rpm and then back up to normal revs again and will continue to do so. when it does occur (which is not all the time! sometimes i can drive for 1/2 an hour and it wont happen but then it will start happening) i simply either put my foot down to get the car to drop down a gear or slide the gear lever over to "steptronic" mode to get it to drop down a gear and the problem stops. i will then lift my foot and let the car go back to its top gear and it will be fine for a while then start happening again....

ive tried to use the search engine here on bimmersport but its been useless.... i cant even get it to bring up any hits for a simple "e39" search....

ive also searched other bmw forums and googled like hell. but as you may now understand its hard to narrow this problem down to a simple google search term...

im thinking maybe the vanos seals need replacing?? or possibly some sensor is going faulty? o2 sensor? exhaust sensor??.... possibilities are endless....

any help, guidance etc fully appreciated

i'd love to get a diagnostic done on it but i live in new plymouth and im unsure of where to take it because as far as i know there are no official bmw service mechanics based here....

thanks in advance

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Sounds very much like you have a torque converter lock up clutch problem. There should be a reliable Auto Trans repairer down there in New Plymouth

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i simply either put my foot down to get the car to drop down a gear or slide the gear lever over to "steptronic" mode to get it to drop down a gear and the problem stops.

"S" is Sport mode. Basically means the RPM limit in each gear is higher and the shifts are slightly firmer and quicker. I think "steptronic" is just a fancy word for an automotic gearbox that has a manual mode. To engage manual mode you shift it over into Sport Mode then push the gear lever up or down. Once in manual you control the gear changes by pushing the gear lever up or down. The car will still change gear automatically in manual mode if the control module deems your speed to be too high or too low.

Had a similar problem, though not as pronounced as yours, on my 540. A service and new trans fluid sorted it out but I'd do as Glenn says and take it to an Auto Trans repairer for a proper diagnostic.

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My mates 540i was doing something similar. It turned out to be a solenoid to do the the lockup I think.

Best to get a trans specialist to look at it - Often, they can drive it round the block and know the problem straight away.

A service is never a bad idea anyway.

Plus, if the box is poked you have an excuse for a manual conversion B)

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