5-Series (E12,E28, E34, E39, E60)Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)
I just bought a 95 740iL, absolutely beautiful car.
It has a couple issues but sense I run a tire/repair shop I think I can deal with them ok.
Needs a tie rod assy and control arm on the right front and some front brake rotors.
Now for the real issue.
It has a rough idle. I've replaced the BOSCH +4 plugs with NGK's, ran some injector cleaner through it and SeaFoamed it as well (3 times).
While it idles a bit better it's still not good.
I stuck a vac gauge on it and it has erratic vac at idle which tells me the valves are not seating properly. 215k miles.
So....... I have a new (to me) 98k mile engine being delivered in the AM.
I would rather not swap engines as I tend to get REALLY carried away, Timing chains, valve cover gaskets, pan gaskets, water pump. etc etc.. I just tend to go nuts.
Last time I did this I ended up completely refreshing the damn "Good used engine" before I even had the old one out.
Welcome to the Werkz. Always good to have another 7er on board.
Have a close look at the intake manifold and the intake ducting between the MAF and the throttle body. My 740iL (M62TU engine) had leaks between the throttle body and the manifold, others have found cracks in the plastic ducting. Way easier to fix up a few vacuum leaks than changing the whole engine.
I am not sure if this could have the effect that your experiencing, its from the later motor, but worth considering. If you start the engine and let the idle settle, pull the engine oil dipstick and listen to the idle and for a slurping noise from the dipstick tube. If the idle drops and you do have a slurping noise it is most likely a diaphragm issue on the intake manifold rear cover (OSV). Not a really big issue, but its a bit of a pain to replace. Given you've got the tools and facilities it is probably a piece of cake for you to change. Have a look at part #2 in this diagram. RealOEM.com BMW E38 740iL Intake manifold system
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