Things I can do to keep M20B25 reliable

[cheeunit890]

Hey R3v,

2 years ago I made the mistake of purchasing an E30 without doing proper homework on the past service history (my fault). Since then it's been unreliable and I rely on this car as my daily driver. So I am reaching out to ask for your guys' advice. I know that these cars can be reliable with the proper maintenance so I'm using this as an opportunity to learn how to maintain this car. It seems like the past owner neglected a lot of maintenance that is in my lap now.

Goal: I'd like the motor to be reliable as a DD. I drive around the City a lot for my job.

Motor Specs:
M20b25, 129XXX miles

What's been fixed since ownership:
Timing belt & water sump pump
Center support bearing and guibo
New radiator, new coolant hoses, new thermostat
Main crank seal
Engine mounts
Tie Rods
New springs & struts
Fuel pump & fuel lines

Issues I am aware of:
Needs a new driveshaft (mine shakes a lot during top of 2nd gear which is probably killing the new guibo disc...)
Inspection II light turned on recently (I think I addressed a few of those issues with my fixes though)
My rotors likely need replacement soon. There are grooves in the discs. Already got new brake pads.
Head gasket leaks oil

Question:
What preventative maintenance can I do to make sure this thing works reliably? This is my first real car that I am learning to work on myself, but given that I work 6-7 days a week it's hard to find time. Winter will be a slower time for business so I'm hoping to do as much DIY work on the car before the year.

Thanks so much - it's been an amazing car but it's also been very unreliable since I've gotten it. I want to keep it if possible.

Thanks,
Craig

[packratbimmer]

The E30 can be reliable after the back maintenance is caught up. I jump in mine (89 325iM) and do 1.400 mile trips after just checking the oil: I also let my mom use it for 9 months last year with zero problems. Great car!

Sounds like you are on it, but I would get on that driveshaft right away as you can tear up other bearings, the U-joints and such. Also, I would take a good look at the rear subframe bushings as they are often neglected and looked over - vibration from those bushings can transmit through the whole car, cause additional problems and be annoying. That should get you started - sounds like you are a busy man!

[cheeunit890]

Thanks for the info! Definitely busy, I am a Realtor in SF.

Aside from the driveshaft, is the oil leaking from the head something I should be worried about? The car is also likely overdue for a valve adjustment. I would probably leave both of those to a qualified shop since I don't have the knowledge to do either yet...

The E30 can be reliable after the back maintenance is caught up. I jump in mine (89 325iM) and do 1.400 mile trips after just checking the oil: I also let my mom use it for 9 months last year with zero problems. Great car!

Sounds like you are on it, but I would get on that driveshaft right away as you can tear up other bearings, the U-joints and such. Also, I would take a good look at the rear subframe bushings as they are often neglected and looked over - vibration from those bushings can transmit through the whole car, cause additional problems and be annoying. That should get you started - sounds like you are a busy man!

[dnguyen1963]

Not sure if you meant oil leaks from the head or the valve cover. Valve adjustment is very easy to do. There are a few videos on YouTube that shows you how to do it. You really need to learn how to do minor stuff yourself or the cost of ownership will make you walk away from the E30 soon.

[squidmaster]

You probably only need a new guibo and not a new driveshaft. It's a very common issue especially at this age

[cheeunit890]

Not sure if you meant oil leaks from the head or the valve cover. Valve adjustment is very easy to do. There are a few videos on YouTube that shows you how to do it. You really need to learn how to do minor stuff yourself or the cost of ownership will make you walk away from the E30 soon.

Agree 100%. I want to learn how to do those things. It's been hella hard with work but I'm going to take some time off in December and learn to do these things myself.

You probably only need a new guibo and not a new driveshaft. It's a very common issue especially at this age

Already replaced the guibo so definitely not that. Another shop I took it to for an unrelated fix prescribed the driveshaft.

Thanks so far for the help guys. I'm new to working on cars but I'm determined to learn.

[Mook613]

If you're car is shaking only at the top of one specific gear then it doesn't sound like it's your driveshaft.
Your driveshaft spins based on the transmission output and its rotation is directly correlated to your wheel speed (through the ratio of your differential). So a shaking of the driveshaft would happen at specific speeds, not just in one gear; it would happen in any gear at that speed.

Check your transmission mounts.
Otherwise it may be a transmission issue, but those typically just make noises and not shaking.

[digger]

injector refurb
good oil
flush and replace fluids periodically
valve adjustment/checks

[Streichholzschächtelchen]

If you like thrashing it rockers have a tendency to snap. You seem to have the rest about covered.

[packratbimmer]

If oil is leaking from the head gasket directly between the exhaust manifolds your head might be starving for oil, especially at high RPMs.

[Tinkerer007]

Keep an eye on the battery voltage for an indication of alternator brushes wearing out.

(I have an extra voltage meter that fits above the radio if you have spot available. ~$25).

[cheeunit890]

If you're car is shaking only at the top of one specific gear then it doesn't sound like it's your driveshaft.
Your driveshaft spins based on the transmission output and its rotation is directly correlated to your wheel speed (through the ratio of your differential). So a shaking of the driveshaft would happen at specific speeds, not just in one gear; it would happen in any gear at that speed.

Check your transmission mounts.
Otherwise it may be a transmission issue, but those typically just make noises and not shaking.

Thanks for the advice. I paid attention today and noticed it's between 20mph-25mph. So it's speed related, not gear-related. Shake isn't that bad but I should address it before it affects other parts.

injector refurb
good oil
flush and replace fluids periodically
valve adjustment/checks

I run Rotel 5-40w and just flushed the system w/ new coolant. I think next up will be transmission oil and brake fluid (will be doing this soon w/ the brakes).

If you like thrashing it rockers have a tendency to snap. You seem to have the rest about covered.

Will keep that in mind! I drive spiritedly but I wouldn't say I thrash the car very hard.

If oil is leaking from the head gasket directly between the exhaust manifolds your head might be starving for oil, especially at high RPMs.

Will recheck where the leak is. Engine does require regular topping off of the oil.

Keep an eye on the battery voltage for an indication of alternator brushes wearing out.

Good call. I replaced the battery 2 years ago but I should definitely keep tabs for that too.

Aside from those things above, I noticed that my car sometimes turns over very weakly/slowly. Other times it starts up very strong. Would this be fuel related? What would cause inconsistent startups?