525i stalling issue - need help

Hello! Newbie from Ohio here. Found you guys while reaserching a problem on line, figured mabey I could get some help with a problem.
I just got a screamin' hot deal on a vary nice Black on black 1990 525i for just $650 (2.5 w/ auto, 159kmi). Naturally for the price it needs some work, but it is in vary nice shape cosmeticlly. I'd post photos, but don't have any in my computer yet.
Car runs and drives, but has a vary bad problem with stalling and poor idle. Check engine light is on, was told by seller this is because of large cracks in the plastic air filter box letting too much air into engine. (already planning to replace it), but i'm thinking there's more to the check engine light being on. Just bought the car a couple days ago, so I have not had the chance to get it to a mechanic to run the trouble codes.
Initial engine start up is OK when engine is cold. Engine has to turn over 5 to 10 times before starting. Given the age of the car i'm not suprized it doesn't fire up right away. While in park engine does not stall if I just let it idle, but does have poor idle. Seams to idle around 500 - 700 RPM, then stall if I give it any gas. Tries to stall when in gear (when under load) and at red lights. Worst stalling has been at red lights. Giving it some gas causes vary ruff idle / bogging down of engine, does not want to rev up well. Pretty much have to floor the gas pedal to get it to rev up, and still ends up stalling as soon as I let off the gas. Once RMP gets to around 2500 it smooths out. Once engine stalls out, it is hard to start it again. Engine cranks over vary well, just does not want to start back up again. After about 30 seconds to a minuet of cranking the engine, it sloooooowly starts to fire up. Does not seem to be an issues while driving down the road, just while parked or stopped.

What i'm thinking is an idle control valve or a bad throttle possision sensor?

Could the broken air filter box have something to do with it?

Mabey a vacume leak?

Gas tank was empty when I test drove the car, would crap from the bottom of gas tank cause these problems?

I don't think it is a matter of needing a tune up, last owner did a bunch of work, so I don't think the car has been neglected.

I've already paid for 1 tow, hoping to not have to tow it again.

This is my 2nd BMW (used to have a 733i), I know cars & and i'm mechanically inclined, but i'm no pro, and only have typical tools (no diagnostic tools) and a driveway to work with. Any help with figuring out & fixing this issue (or many issues?) will be greatly appreciated.

Thanks!

First of all, welcome to the Fest There are a variety of things that could be wrong. You will just have to start eliminating the problems.

First things first - Do the stomp test to check your error codes (bet you thought you had to pay someone to do this didn't ya). Here is a valuable link that has that information in it. It is one of the sticky's at the top of the forum. http://www.bimmerfest.com/forums/sho...d.php?t=525152

Go from there.

See my responses in red below.

Originally Posted by jays525i

Hello! Newbie from Ohio here. Found you guys while reaserching a problem on line, figured mabey I could get some help with a problem.
I just got a screamin' hot deal on a vary nice Black on black 1990 525i for just $650 (2.5 w/ auto, 159kmi). Nice. Be prepared to put a little money in it and you may have a great little daily driver for cheapsNaturally for the price it needs some work, but it is in vary nice shape cosmeticlly. I'd post photos, but don't have any in my computer yet.
Car runs and drives, but has a vary bad problem with stalling and poor idle. Check engine light is on, was told by seller this is because of large cracks in the plastic air filter box letting too much air into engine. (already planning to replace it), but i'm thinking there's more to the check engine light being on. Just bought the car a couple days ago, so I have not had the chance to get it to a mechanic to run the trouble codes.
Initial engine start up is OK when engine is cold. Engine has to turn over 5 You can do this yourself with the stomp test. See the info below. to 10 times before starting. Given the age of the car i'm not suprized it doesn't fire up right away. While in park engine does not stall if I just let it idle, but does have poor idle. Seams to idle around 500 - 700 RPM, then stall if I give it any gas. Tries to stall when in gear (when under load) and at red lights. Worst stalling has been at red lights. Giving it some gas causes vary ruff idle / bogging down of engine, does not want to rev up well. Pretty much have to floor the gas pedal to get it to rev up, and still ends up stalling as soon as I let off the gas. Once RMP gets to around 2500 it smooths out. Once engine stalls out, it is hard to start it again. Engine cranks over vary well, just does not want to start back up again. After about 30 seconds to a minuet of cranking the engine, it sloooooowly starts to fire up. Does not seem to be an issues while driving down the road, just while parked or stopped.

What i'm thinking is an idle control valve or a bad throttle possision sensor? Both of these are distinct possibilities.

Could the broken air filter box have something to do with it? Depends on where the crack is. If it is before the mass air flow sensor (i.e. on the side closest to the front of the car prior to passing the AFM), then that should have no bearing on it. If it is after the AFM, (i.e. between the AFM and throttle body), then yes, that can cause problems because the air is not metered and will cause improper air/fuel ratios.

Mabey a vacume leak? This is another disctinct possibility. Inspect the intake boot and all associated vacuum lines carefully. With the car running, you can spray some carb leaner in specific areas on the intake side. If the idle suddenly jumps or improves, there is a vacuum leak at that area.

Gas tank was empty when I test drove the car, would crap from the bottom of gas tank cause these problems?
Possibly. The fuel filter may be clogged or the pump may be providing insufficient pressure or volume. If necessary, check fuel pressure at the fuel rail with the car off (to determine static pressure in the system) and with it running. Compare the values to the Bentley manual.

Oh yeah, I haven't mentioned the Bentley manual. Here is a link to a searchable version: http://www.bimmerfest.com/forums/sho...hlight=playboy This is a must if you are going to do work on the car. Get to know this manual well and you will be well on your way to figuring the problems out. It sounds like you have the knowledge and ability to do so

I don't think it is a matter of needing a tune up, last owner did a bunch of work, so I don't think the car has been neglected.

I've already paid for 1 tow, hoping to not have to tow it again.

This is my 2nd BMW (used to have a 733i), I know cars & and i'm mechanically inclined, but i'm no pro, and only have typical tools (no diagnostic tools) and a driveway to work with. Any help with figuring out & fixing this issue (or many issues?) will be greatly appreciated.

Thanks!

Good luck and please update us on your progress. Again, welcome.

Thank you, tons of good info there.
As far as the air box being broken, it has at least 3 large cracks on the flat part, in the front of the box, going around where the tube meets the box. The box needs replaced evan if this is not the cause of the stalling problem.

gday champ ,as one of our e34 lovers said, 2nd hand cars need money spent on them.....as well as that if you are wanting to keep the beast do a full service on it air filter, fuel filter ,oil filter plus ''ALL'' oils , you dont really know how much attention it has recieved. mate if that fuel tank sat dry or even with old fuel in it run some premium fuel in it every 2nd tank 2 or 3 times...as was said most of ya probs are air leaks causing it to miss and fart and carry on.when you done all of wat old mate went through and if its still runnin like a bag of **** , get that injector fuel rail out....that after all the crap i checked and replaced was the problem....cheers jay.