Bmw 740 95reg miss firing

[holty]

Hi this is doing my head in. Bought it a while back as it looked nice with the alpina kit . All went well after 30 miles or so. Then it started running on 4 cylinders. Took it to a so called bmw specialist after my own mechanic decided he didnt want to dissapoint me, he diagnosed coils on one side. Still no good after, about 10 miles of running. I changed the other side with matching. Got other mechanic to have a look, after persuading and found the exhaust system to be blocked with what looked like old cat.... Still not running well after a few mile .Well if i disconnect battery for a while the car runs ok for a few miles, or till it decides to misfire. Now looks like its not running on the drivers side of the four cyliders. But getting voltage to the coils, but no switching voltage. Strangely its been on the diagnostics etc but throws no major fault codes. Plus the engine management light doesnt come on. Had the ecu looked at and test unit. But still problem persists. Please help !!!!!

 

[nickso]

Whats the mileage on this? I had a similar if not identical issue with an E34 540i (same M60 engine) that I never fully got to the bottom of but did improve to 99% working so I could blow the gearbox

Problem with the E38's is they are packed with electronics and most of it is probably coded meaning big bills. If I were you I would check all the basics thoroughly and then if not cured sell it on. Spark plug wells fill with oil if the rocker gaskets are gone and the cyclone valve will likely be full of gunk but that usually sees a James Bond style smokescreen emitted occasionally from the tail pipe if its really bad. Crank/cam sensors are pretty crap and tend to work ok when cold but not so good when hot causing faults not unlike yours.

Last good BMW's were the E34 and E36 (although the interior of the E36 is a little cheap) Any other BMW after that and over 100k is a liability and just waiting to rape your wallet. For my next one I'm going back the way to a nice E34 M5 I think.

 

[holty]

Thanks nickso its a 95 reg e38. Milage is 160000 And my wallet is already crying. When i did buy this it was delayed to be picked up due, to the a faulty cam sensor. Wandering if he put a cheap version on. My gut feeling is now a sensor as no switching voltage is being applied to one bank of cylinders?. Luckily this has 19" alpina wheels on it, in perfect condition. So might get some money back. Only paid £1400 so not all at loss. Really got to stop buying cheap old cars already hav a 96 scooby and 1.9 205 gti. Was looking at a mondeo st 220 that was cheap yesterday

 

[nickso]

I bought the 540i for 1200 quid....was 8 year ago so was a bit pricey for 186k miles but it was in near mint condition......sadly the dreaded 6 speed box 2nd syncro problem fully reared its head after a sound thrashing of a Subaru loser.

If the cam sensor has been changed I would check that first. The BMW stuff is dogshit so a chinky version will be worthless. They are almost impossible to check properly as they only fault when hot and it's almost impossible to replicate the fault.

Cheap old cars are the best....I have lost several thousand on them and will lose much more in the future on them...it's part of the game