In Reply to: 2.5 24v sport..Erratic.. posted by Pete on November 02, 1999 at 14:55:47:
: I own a 525isport with really high milage , it seems to run fine when it`s warm , but it`s really erratic when it`s cold , sometimes it`s better than normal , another time it kind of hunts , but as soon as it`s warm it goes really well , can I check anything without booking it into BMW dealer , who here in UK charge equivalent of $100 per hour , I also have hesitant oil pressure from cold , maybe 2-3 seconds before oil light goes out , together with top end rattle , which dissapears when light goes out....(218,000 miles)...look forward to hearing..
When you first start up a cold motor the oil is thick and takes a while to get up to the head. A hi miles car may have a little wear that may prolong the time it takes oil to get to the head where the tappets may rattle a bit. Not a big problem. Try a synthetic oil to help this. Synthetic will get up to the top faster. Here in Pennsylvania, USA we have Castrol Syntec, the 5w50 would do nice. 2-3 seconds on the lite is a bit long but then the sensor may be a bit lazy after a billion miles. The hunting of the cold motor might be due to being in open loop on the Motronic while the Lambda sensor(O2) warms up. Throw in a little vacuuum leak and it hunts more. AND throw in a little extra blowby gas into the crankcase from a well worn set of rings and the car's Motronic will swing till it switches to closed loop and the Lambda takes over. The 5W50 synthetic would be my recommendation and find the little vacuum leaks. Probably turn 300k!