I read through your thread. You mother did not trash the car at all, but she is not an enthusiast if she can't recall when she did a valve adjustment or refer you to her regular mechanic who can tell you that.
That means you have a 210k old E34.
Now you have two choices. You can continuously, over the next 3 years, make posts to the list asking for help with running problems, with no start issues, and other stuff, or you can do it all ahead of time at one go, sit back, relax, and wonder why other people are making such posts.
The difference is just $500 in *oem* parts and about 1 day of DIY time on your end that I know you have the capability to do. By the end of next weekend, you can be that guy who has a reliable E34 that drives superbly. If you don't have the money for this right now since you're in school etc, borrow it from you mother or someone and pay her back over the next 6-12 months.
I think you're one of the more intelligent young guns on the list, in contrast to others who drift in the darkness and nearly kill their girlfriends and try to pass it off as cool. I hope you make the right choice.
All that I'm going to recommend to you here concerns components that either WILL go wrong on an old bmw, or WILL be at less than optimal levels, enough to cause poorer fuel economy, engine performance, or a host of unpredictable and difficult to pinpoint behaviours from time to time. $500 is small beer compared to the original cost of your E34 which was $40,000. The costs of repair are so low because we can tell you exactly what is needed, and practically everything here is a DIY job so you save on workshop charges.
I've been on this list for many years and have owned an E30, E34 and an E36. Trust me when I say that I've been through it all. I am certain about what I'm talking about. Its easier and better to do it all at one go.
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First, kill your common no start issues (and everything here is oem unless otherwise stated).
1. Fuel pump. $110 shipped Bosch.
2. CPS. $60-$90, either valeo, bosch or meyle.
3. Fuel pump relay. $15.
4. Check your battery's reserve charge / cold cranking amps (CCA) on an appropriate digital meter. Usually just a small tip or for free at a shop, autozone and about 10 minutes work. If its under 35%, you need to revive your battery ($40 for the kit), or purchase a new one.
Check your suspension bushings. If they are not bad, and if in doubt consult us over here, then go onto the following :
Maintenance
5. Clean out your air filter (Please see. ) or change it to a new one $15.
6. Change to a new fuel filter $20. Very old fuel filters cannot be rinsed out from what we've seen.
7. Change your ects. $25.
8. Change your ats (air temp sensor). $20-$25.
9. Change or seal up your intake boot and your vacuum lines. Anything from $5 (silicone high temp non-gasket sealant) to about $80 for the whole set of various hoses. Not essential, but highly recommended. Check everything else.
10. Do your valve adjustment. New valve cover gasket ($25) and shim tools required (not sure how much but not expensive. If its expensive borrow from MSD).
11. Clean your plugs if they don't look damaged. Better if you get new ones if these are old. Copper ones will be fine ($20 for a set) and Bosch Plat+4s highly recommended ($45)
12. Check your rear differential fluid. If its dark or black, change out. Your fuel economy will improve, and your rear diff bearings and gears will not get destroyed. Costs $10-$20.
13. Diesel flush your engine at the next oil change. Add diesel 3 quarts of diesel to your empty fuel tank with an immediate full fillup, at the fillup following the filter change, for fuel injector cleaning.
14. Clean your throttle body off all carbon.
15. Clean out your ICV.
16. Change the one way valve on the brake booster. $15. Optional but recommended : change the brake booster's vacuum hoses, clamps, plastic fitting and rubber grommet. Will cost an additional $30-$40.
17. Get a new throttle position sensor. $45. Safety issue. Old sensors have been known to cut out the engine while driving.
18. Step down your blower motors fuse to 20A. This can help prevent fires. It is currently 30A.
19. If you recently flushed and replaced your coolant, add 1 quart of 40% concentrate sodium silicate to your expansion tank ($10 from a pharmacy) and run the engine at idle for 30 minutes. If not, wait till your next flush and coolant refresh and do so at this time. Sodium silicate seals micro cracks and tears in HGs and cylinder heads, and is coolant friendly. This is cheap insurance for your engine.
20. Consider tuning your AFM. MSD will explain further.
23. Clean your ccv fitting and test for vacuum leaks on it.
I just did a tally. All of the above comes up to $455 if I exclude optional items and the battery. Looks like I'm 13% under budget. ALL OEM-GRADE PARTS. Cost of parts? Around 1.1% of the original purchase price of this car, and that will give you headache free motoring for the next 7-10 years. And doing all the above will save you money at the gas pump through better fuel economy and will give you more driving pleasure through better performance, which is worth the investment anyway.
Oh dear. Forgot. You have the M30. The following applies to all timing belt engines (M20, M30).
14. Highly recommended that you get a new dizzy cap and rotor. You don't need new wires. However, this would not be cheap - $100-$200 oem. So you can wait till you have a problem if you wish. Consult MSD about when this is necessary. He may know how to efficiently and accurately test your existing units.
15. Timing belt ($20) and bearings (not sure but at least $50), depending on how old yours are. Consult MSD about when this is necessary. When it is necessary, it is necessary and not optional.
Please order all of the parts above and get it done all at one go for maximum efficiency (and also to probably enjoy maximum discounts). Or schedule to do them progressively over the next 12 months. Don't wait for a problem. That's silly when there's so much corroborating evidence about these cars accumulated independantly and over many years.
Good luck.