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First time BMW owner. Just purchased a 1990 525i. Help?

18K views 79 replies 11 participants last post by  BMR_LVR 
#1 ·
So I just bought his car today. Kind of an impulse buy, but from everyone I talked to it was a good deal. It's in amazing condition for being a 90' and having 150,000 miles. I paid $1800 for it, it has no mechanical issue and runs well and like I said is in amazing condition. Did I get a decent deal? Regardless, the car is mine. So I have a few questions. What kind of problems should I look out for? What things will I come to love? What kind of aftermarket parts are available and should I even bother with them? I know very little about BMW's but assume they don't need anything aftermarket to drive amazing. Thanks for any help, I'm extremely excited to own this car and can't wait to start workin on it and driving it.
 
#2 ·
Your car has the M20B25 engine which I think is a fine engine but others say it is too underpowered.

Your particular engine is very easy to work on and will run a very long time with the proper maintenance.
First think this:
Has the timing belt been changed, any records?
How about the waterpump?
When was its last oil change?
When was the last cooling system service?
Anything unusual about the fluids?

Answer all of these questions, then take a look at this:
http://www.bmwe34.net/E34main/Trouble/What_will_break.htm

If you have any other questions please feel free to ask, all of us are here to help.
Welcome.
 
#3 · (Edited)
Awesome, thanks for the reply that's exactly what I was looking for. I can understand the underpowered comment, I felt like it it would have more pick up to it but it doesn't bother me. As far as all the questions on maintanence I'm not sure. The first thing I'm doing this weekend is doing a complete tune up (iridium spark plugs, all filters, change oil ect.) then I'll go from there. I know the previous owner put a brand new radiator in it, an I want to say a new water pump as well. I'm guessing I should replace the timing belt as well when I do the tune up? Thanks again for the post really helps out.

Edit: also, just did a quick google search for aftermarket stuff for fun on my lunch break. I came across a chip (gfchips) that advertises 60hp ,30ft torque and 4-7 mpg increase. Only for $70. Sounds like bull****. Any opinions?
 
#4 ·
Sounds great!

FYI: These older engines respond better to copper plugs, but its up to you. I would use copper.

AS far as chips, as long as they are brand name chips (WAR, TMS, etc.) you will be fine. You must use 91 octane fuel or higher wen you get a chip since all it does is re-map the fuel controls to work with higher octane gas as opposed to the stock chip which optimizes use for low octane fuel.
 
#6 ·
Yup, just like the 1989 owners manual says:


The stock ECU has a stock tuned chip from the factory. The stock chip works with 87 AKI.
The performance chips they sell out there (legitimate ones) are tuned to work with 91 AKI.

So, if you buy a performance chip, you are just replacing the old one.
 
#7 ·
So just an update. My first impressions are great. Love the quality of the vehicle, am amazed at the features it has for a 1990 model, and only have a few things I need to fix. The latch for the glove compartment needs replacing. The paneldor the sunroof needs to be replaced( where the buttons are). It may have a fuel problem, as sometimes it won't start the first time I try. Perhaps fuel pump? Also, sometimes when I'm slowing down (braking or just coasting) I feel a very slight jerk. Makes me think downshifting isn't proper but that's a pure guess. Overall, very glad I bought it and can't wait to start fixing things and making it even better. I'll take some pictures and post them tomorrow.
 
#8 ·
Great that you are getting familiar with it!

There are two screws for the glovebox latch once you get it open. It comes apart in two pieces, junkyard item.

The panel can also be found at a yard. If its only the clips that are broken you can make your own holding tabs. I made mine out of plumbers tape!

Perhaps its the fuel pump. Can't know for sure without running fuel pressure tests.
Check the Bentley manual for testing the Fuel pressure. The manual can be DL'ed here:
http://www.bimmerwerkz.com/forum/5-...ey-service-manual-e34-updated-10-a-42558.html

The jerk may be because of an improperly adjusted kickdown cable at the throttle body. Follow the instructions for adjusting it in this thread, you may need a feeler gauge:
http://www.r3vlimited.com/board/showthread.php?t=225936
 
#10 · (Edited)
I have a 1993 521I touring, with the stock chip can I run 87 octane fuel, and would a performance chip give me increased hp and torque as advertised? Thanks
Mister, don't threadjack...

Your engine is an M50. What you need to find out is if it has VANOS or not. The M50TU has VANOS and the M50 does not.

If you have the M50 then Premium fuel is required for best performance, otherwise you will experience knocking.
IF you have the M50TU then Premium fuel is not required since the engine is equipped with knock sensors to compensate for lower grade fuel.

If you do buy a performance chip you MUST use Premium fuel since that is what the chip does. It re-maps the injection for use with Premium fuel only (91 AKI or higher). Otherwise you will not see an increase in HP or Torque.

Byork and I do not have to use Premium fuel with our stock chips because we have the M20 engine. It was made to be used with 87 as stated above.
 
#11 ·
So I'm trying to learn more and more about my car and what I can do to maintain it. So far, I've heard a few things that if possible I would like clarification on. I was told the m20 doesn't need high octane fuel but responds better with it. Will I notice a difference if I use say 91 or 93 with the stock chip? Also, I was told that changing all the speed sensors is recommended. True or bull****? One last thing, I want to clean up the engine as best I can and from then on take great care of it. From what I can tell its been taken great care of so far but I would like to clean it out and get a fresh start so to speak. I was thinking of using motor flush, then changing the oil and putting in some engine treatment (zmax was recommended to me). Good idea or no? I'm not very car savvy but am a quick learner and am very interests in learning all I can about bmw's , mine specifically.
 
#12 ·
You should focus on replacing ALL of the fluids before you start eating through petro products with an engine cleaner. Brakes, radiator, transmission, gas filter(if your model has one) Focus on that first. It'll give you a baseline for the car, and you'll insure its longevity.

After that read the error codes with a stomp test. Then fix whatever comes up. Then you can chip it since you know your transmission and radiator aren't trying to pump cow pies through a tube while you're flooring it. Good luck.
 
#15 ·
I tried that exactly and nothing happened. Ill give it another try and see if it works. My check engine light isnt always on, it usually on clicks on when im in idle or park for a small amount of time, then as soon as i give it gas it goes away.

Update:
Finally gave the car a wash. Was told it might have a small exhaust leak so i went to get it checked out and ended up putting a new cat converter and muffler on it. Just sold my truck today so this weekend is tune up and fluid change time. Pics will come as soon as it dries.
 
#17 ·
If this is a long term buy get the manual. The EFI settings will need checking (throttle position etc) and the air flow resistor may need cleaning, O2 sensor change and the throttle by-pass unit cleaned and checked. I would not use 'flushing agents' just service at half the standard period. An injector clean (removed in a test rig type clean) may be a good idea.
 
#18 ·
So random question. But whats a 1990 730i worth? It has 90,000 miles, motor is in great condition, so is exterior. The inrerior needs work though. My friend offered me his for $900 and im thinking of getting it, fixing the muffler and the interior with a $1-1500 and selling it for profit. Good idea?
 
#19 ·
Just wanted to add a couple things here. Do your tune up and change ALL fluids.

However!

I don't remember if you have a auto or manual. If its auto I wouldn't mess with it or drain anything out of it. They are notorious for failing after a fluid change! If it's manual then definitely change fluid.

DO go to www.bmwe34.net
It's full of awesome info. Ask people on here when you get confused. And get yourself a E34 Bentley Repair Manual (amazon it). It E34 owner's bible.

If you want to clean everything in the inside of your engine I would suggest researching all you can do with SeaFoam. It's amazing stuff!

Also the front control arms are renoun for going bad. The car will shake terribly bad when you hit the brakes at 50-65ish mph. That's how you'll know when those are shot. In fact check all parts in the steering system.

And check shocks too. All you need to do is push down on one corner of the car at a time. It should feel very stiff and should have very little give. If you can push it down more than a fat inch or you can rock it, then you shocks are toast.
 
#24 ·
Haha yes my cat loved it. So i just bought some ceremic brake pads for the front and back on eBay ($85 for both, shipping included) and am slowly doing small replacement/upgrades as well. While i was looking at my car today i noticed this, and was wondering if anyone here would have any information on it. Do you think its a big deal? Any advice on how to fix it?

It looks like a small amount of rust is forming near the bottom of the doors behind the plastic trim.

 
#25 ·
Hey Byork. I would get the rust looked at as you do no want it to spread. I you are body work savvy enough, you can sand it down yourself a bit and see that it hast spread under the paint further. My brother does body work, I am going to see him tomorrow so I will ask him for his thoughts an get back to you. By the way, congrats on BMW! I have an 06 325xi and love it!
 
#28 ·
Awesome thanks a lot. That would be of great help. And yea i love it more and more each day, very happy with my purchase.

Get it fixed soon. The doors have two thin skins, if that is rusty like that I bet the inside skin is starting to rust too. Unchecked this will lead to a new door faster than you think. Although I'm from Wisconsin, what would I know lol
Not what i wanted to hear but i knew rust is never good so im not surprised. Thanks for the information. Even though youre from wisconsin it still is probably true. Especially me living on the coast and our humidity almost always being 80% rust is very common here.

That trim pulls off straight down. No clips. It fills with dirt and holds water. take them all off, clean them out and check/repair body work. Keep the door drain holes clear.
So it just has some glue or other adhesive holding it on? How would i go about putting it back on, or are you suggesting to just leave it off? So to take them off i just grab and pull down? Thanks for the info kind sir.

Another update. Finally got the money from selling my truck so i ordered some NGK Spark plugs off eBay. During my lunch break im going to see if i can find some nice new cheap filters on their too, if not ill just get them through my work. Then it will be tune up time!
 
#26 ·
Get it fixed soon. The doors have two thin skins, if that is rusty like that I bet the inside skin is starting to rust too. Unchecked this will lead to a new door faster than you think. Although I'm from Wisconsin, what would I know lol
 
#27 ·
That trim pulls off straight down. No clips. It fills with dirt and holds water. take them all off, clean them out and check/repair body work. Keep the door drain holes clear.
 
#30 ·
Gotcha. So new problem developed today. Since we finally got some rain, i decided to fix my wipers. When i bought it the driver side wiper was missing, and when i noticed it was a reverse j hook style blade i decided to tackle the problem later as i had no idea how to fix it. Well, the time has come. I found out how to modify a normal j hook style blade to work, so that is fixed. However, while using my wipers today my passeneger side blade stopped working. It doesnt fully extend, if at all. The blade seems to long and hangs over the windshield. Anyone have any ideas as to what could be my problem? I tried various blade sizes and all produced the same problem so i know it has to do with the motor or something.
 
#33 ·
Muchos thanks sir. Got both sides working now. Just did my tune up over the weekend. Noticded a small but significant improvement in power and driveabilty. The old spark plugs were not copper, so i think my change attributed to that change in performance. Also ordered some lift support arms for my hood, as mine are shot. I noticed a small oil leak, but its looking like it just needs a new valve cover, so im picking that up today and fixing that issue. Next will probably be me getting some fuel injector cleaner for it. My mechanic neighbor told me about some really good stuff that dealers use and only dealers sell (not at autozone, o'riellys, advanced, ect.) I think he called it BG42 or something like that. Then, just little things over time to ehnace the drivebaility and power.
 
#36 · (Edited)
In the tune up category of things :

1. Check that all engine belts are properly tensioned. They should be tight to the touch. Loose belts rob your engine of power. Use belt spray on the belts and see the difference in its performance...that's what tight belts will do for you.

2. Replace air filter. If the current one looks ok, dust it off. You can also soak it in laundry detergent for an hour and rinse off with running water. Drip dry and reinstall even if damp. It will dry out in normal driving. No danger to the engine.

3. Clean out your throttle body. Remove main air hose and spray carb cleaner into the butterfly valve area to eliminate any crud. Inspect the air hose for any cracks before your reinstall it. If there are cracks, purchase a new one, its fairly cheap.

4.1 Do a diesel flush on your engine. Add 1 quart to your crankcase with the old oil, run the engine at idle for 15 minutes, then drain and replace oil and oil filter. Do this each time you service your car.

4.2 Use the correct oil rating for your engine, or use something slightly thicker at first and then see how it feels when you switch back to the correct rating down the line. If the thicker oil feels better, stick with that. If they both feel the same, switch back to the recommended rating.

5. Do a diesel fuel system flush. Add between 1-3 quarts of diesel to a nearly empty fuel tank, and then immediately fill up to full with regular. This causes the fuels to mix. Then drive normally. The diesel in the tank will clean out your fuel injectors better than any injector cleaner....and for the same price, you'll get a much higher volume of cleaner. If this is the first time you're doing this for your car, add diesel for 2-3 consecutive fillups. Thereafter, do this once each time you service your car.

6. Go for a WOT (wide open throttle) run on your car. Get those rpms to the 5k zone and hold it there for 15 minutes. If you cannot do this at safe speeds where you live, switch your transmission down to 4th or 3rd gear to get the rpms up.

7. Seafoam's effects are psychological. Any real benefit to the car comes from the fluid mixing with the engine oil and thinning it out. You can get the same effect by adding 500ml of dex3/4 transmission fluid to your engine. Its perfectly safe and will thin down the oil, giving you a short term boost. Marvel mystery oil works the same way too. I've tried all of that to no genuine effect.

8. Instead of adding sea foam to the engine, add a mixture of 50% ethanol and 50% water to the intake manifold via a tube fed into the brake booster's usual fitting. Anything from 1-3 quarts will be fine. Start the engine and hold the rpms at 1500. Hold the open end of the tube right at the surface of the mixture, without dipping into it entirely...the mixture will be sucked in via the engine's vacuum through the hose, and it will do some cleaning of your intake manifolds from the inside. Hold it at that position until you get the hang of it. Don't worry, you won't hydrolock your engine. Some water will enter your engine though and you might find the oil under the crankcase cap and dipstick a little milky...do not worry, anything from 15-60 minutes of total driving time depending on how much mixture you used, will vapourise and expel the water naturally through the crankcase ventilation system. There will always be water in the air and in oil so your engine will not be damaged. You don't need to do this immediately either, just go for a drive within 24 hours. You can drive normally i.e. hard. :) No issues.

9. You have the M20 engine, right? There was a post I spotted on bimmerfest a long...long time ago, which showed that seriously thick crud accumulates around the two bends of the intake manifold...the first bend midway and the second bend where it connects to the cylinder head. It was a nightmarish picture, and the poster concerned didn't realise anything was wrong at first...he had dismantled it in the process of getting to the head gasket, then saw the abomination and alerted us....I would very strongly advise you to pick up some new intake manifold gaskets, dismantle it and clean it out thoroughly using a flexible probe and lots of flushing. It will surely improve the airflow into your engine and thus your performance and mileage.

When you reinstall the manifold, make sure you use a torque wrench and have the bolts torqued down according to the Bentley manual's recommendations, and in the correct sequence. (This is highly important for the valve cover gasket (vcg) too ).

10. Check on your valve clearances when you do the valve cover gasket. Gap them and tune them up properly. They would have run out for sure. This makes a very noticeable difference to the performance and smoothness of the engine. The Bentley manual has details.

11. Unless you have evidence that the ignition coil assembly/ ignition distributor/ distributor cap / thingamajig and the spark plug wires were recently changed, purchase a whole new one. OEM. Would usually improve performance slightly, and eliminate problems due to degraded wiring. Around $200. I would only get to this after everything else has been cleared.

12. Use 4-claw spark plugs for better performance and longevity. Do not change them for the next 100k miles. Seriously. Bosch plat+4 will do the trick. However, take them out at least once a year and just inspect them.....spark plug burn marks can sometimes alert you to other forms of engine issues (please google). I believe you purchased the denso plugs, if they were the iridium versions you're good for the next 100k miles there too. An esteemed member of these forums once ran stock spark plugs on his e36 m50 (same engine as on the later versions of the e34) for almost 180k miles, with no real issues. As long as the engine's condition is normal, your spark plugs may only require light cleaning on ocassion. The iridium ones don't even require that.

13. Make sure your tyres are properly inflated. Ebay sells a neat solar powered hand held digital tyre pressure gauge. Something like under $10 shipped. Hang on to that. Make it an unconscious habit to scan your tyres' standing road bulge from time to time to sense problems early, then use the gauge to confirm. In any case, check the pressure every 2 months.

14. Autozone will scan your car's computer for free (or is that only for obd2 cars?). If the stomp test does not work, don't bother, just head right over there and get that checked. After you've had the codes read and noted, clear them on your car. The code reader can do this, or you can unplug your ecu for 5 minutes. Don't be too worried if you find many codes, some of them are very old ones. After they are deleted, recheck your codes about 1 week later. If the earlier codes have reappeared, then you do have a problem and need to decide what (if at all) you're going to do about it.

15. Use a vacuum pressure gauge to see if you have an vacuum losses on your engine, and if so, do your best to trace it. Youtube has many videos on how to use this gauge. It is cheap...under $30 shipped.

16. ** COMMENTS INVITED TO CONFIRM OR DENY ** : After everything has been done, please retune your engine by playing with your air flow meter (google for detailed writeups with pictures). There is a little allen-key bolt over on that afm that you can turn clockwise and anti clockwise to fine tune your idling and get the perfect note. You should do this after everything on this list has been done for two reasons : (a) by then you would have totally gotten to know your engine and how it sounds under various conditions intuitively, which is important for this "tuning fork" type tuning, and (b) anything else that might affect the engine has been replaced, cleaned out or upgraded. This should be the very last step. And it is reversible. The target, is to make it sound as sweet as possible when at idle. What does that mean? You'll know it when you hear it. :) You can only determine this after you've had your car and worked on it for a couple of weeks, so only do this at the very end.

cheers, Roberto
 
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