I NEED ALL HELP I CAN GET with idle, hot start issue, and misfire

[liljos]

i'm at the final straw with this car as i am fed up with no results :help
it really breaks my heart since i do love this car and i love bmw's as a whole.


the car: 1990 525i m20 5spd


problem: when the car is cold it starts right away. but there's a bit of an idle problem which i believe relates to the idle control valve. i removed the idle control valve, opened the casing and found that the internals were pretty much done so i will be needing a new icv. anyways, when the car is already running and warm, it's hesitant to even the slightest throttle movement but play with it a little and it'll eventually be fine and rev up. the idle doesn't wanna drop below 1k without having a misfire(or at least that's what it sounds like). the car can be driven without a problem but once the throttle is lifted to the idle position it starts to stutter and will shut down.


now to start the car while it's warm i have to keep cranking it while opening and closing the throttle(doesn't start if i don't do that) or else i'll have to wait till it's cold or has cooled off for a bit to give it another go.


wanting to fix my cold start problem i went to advanced auto parts and autozone and ordered the coolant temp sensor(autozone) and sendor(advanced auto). i also bought new spark plug wires(still using bosch platinum 4+ that i bought the car with) replaced the fuel pump(used the same fuel strainer)


i've tested: ignition coil resistance, crank position sensor resistance, AFM resistance, coolant temp sensor and sendor resistance, the resistance of the wires leading to the ECM for the coolant temp sensor and sendor and CPs, and even the idle control valve which is now removed. every one of the ranges displayed on my multimeter seemed to be within the normal range according to the bentley manual.


i'm trying to figure out why my car is still behaving in such a way. and if you'd like you see my previous posts about my issues they're right below


http://www.bimmernut.com/forum/5-series-bmw/43796-e34-m20-problem.html


http://www.bimmernut.com/forum/5-series-bmw/43670-idle-problem-please-help.html


SERIOUS IDLE PROBLEM. please help!!! - Bimmerforums - The Ultimate BMW Forum (http://forums.bimmerforums.com/forum/showthread.php?t=1706918)


m20b25 problem. help! - Bimmerforums - The Ultimate BMW Forum (http://forums.bimmerforums.com/forum/showthread.php?t=1747037)

[Tash_1991]

Hey mate, can't offer much insight at the moment regarding a fix, but the 525i touring i just got has the same cold start cough and splutter and the idle issue. Although mine is an M50, i can't imagine there would be much difference. The icv could be a good starting point for me, or the other possibility is an air leak, my Audi one, plugged it and no more cold idle issue... It's just a case of finding it...

[liljos]

Hey mate, can't offer much insight at the moment regarding a fix, but the 525i touring i just got has the same cold start cough and splutter and the idle issue. Although mine is an M50, i can't imagine there would be much difference. The icv could be a good starting point for me, or the other possibility is an air leak, my Audi one, plugged it and no more cold idle issue... It's just a case of finding it...actually you might've read that wrong. you said cold startproblem? mines is a warm start problem :/. cold it starts up like a champ for some odd reason. what I wanna know is exactly what the ICV tells the computer regarding idle, any air info or anything else the ICV sends back to the ECM. and why my brand new sensors arent working properly with my car.above you mentioned an Audi, did you use the ICV from the Audi in your BMW? or did you mean you just changed that for the Audi?

[Tash_1991]

I just read the idle issue bit under the bit where u said it starts cold fine. It's been a long day at the track, forgive me for being a little delirious!!

[liljos]

I just read the idle issue bit under the bit where u said it starts cold fine. It's been a long day at the track, forgive me for being a little delirious!!

it's alright, i've gotten used to no one having my situation /:

[tim eh?]

lijos I had almost identical symptoms on my now departed 89 but I never solved it. It seemed to me that the electrical system voltage was always low even though the alt and battery were good, I never did find the source of the problem but I always suspected it to be some mysterious short on an unfused circuit (bc pulling fuses never helped), but I could easily be wrong about that. I pestered the hell out of this crowd for answers, they were very helpful but I never solved it. Sorry I can't help but at least you are not alone. Uh... well... now you are I guess tho sorry bro :(

IIRC unsuccessful attempts to fix problem... r/r entire engine system (coil,wires,etc), rewired alt and starter, battery, alt, starter, most of the relays i dunno i got sick of it then I found a huge rusthole that I had never seen before so I scrapped it and bought a california car.

[genphreak]

Is the AFM output smooth at the lower openings/?
Is the O2 sensor giving the correct output once warm?
Are the autozone senders correct and not a GM replacement? Do the test properly? Do the original ones show different readings?
Is the ICV fixed now? Without the ICV operational, solving trivial issues will be 'non-trivial' to do...

You may have tried everything here already, but you may need to be more scientific to nail the culprit. I would check for oil leaks from the oil pump (it has an o-ring that often goes on M20s that allows air into the engine, and oil to drip out). Also inspect the sump seal (and all its 10mm nuts are snug but not too tight), and the sump-valvetrain air-pipe (its vertical, and hard up against the engine, under the middle of the intake. You can turn it around a little whilst the engine is running (and for the sake of your skin, cold) to see that it's top and bottom o-rings are sealed or not).

Intake bellows often crack/perish where you can't see it, the pipe to the fuel pressure regulator or the brake booster and other little vacuum pipes can go in strange places... make sure the engine has a healthy vacuum at 700rpm or so by removing the oil cap and putting your hand over the hole to seal it. It should suck your palm down a bit and run less healthily once the cap is off.

I'd swap the plugs for a set of factory gapped NGK single or at worst, double electrode plugs. The singles are cheaper and fine for M20. If you have removed your plugs, the seals will no longer be sealing very well, causing air to get sucked in, (they compress and are one-time seals). Chk also the rocker cover for sealing joints and anything else obvious.

And it goes without saying, a compression test and a fuel pressure test should be done.

Injectors? Pressure regulator?

[liljos]

Is the AFM output smooth at the lower openings/?
Is the O2 sensor giving the correct output once warm?
Are the autozone senders correct and not a GM replacement? Do the test properly? Do the original ones show different readings?
Is the ICV fixed now? Without the ICV operational, solving trivial issues will be 'non-trivial' to do...

You may have tried everything here already, but you may need to be more scientific to nail the culprit. I would check for oil leaks from the oil pump (it has an o-ring that often goes on M20s that allows air into the engine, and oil to drip out). Also inspect the sump seal (and all its 10mm nuts are snug but not too tight), and the sump-valvetrain air-pipe (its vertical, and hard up against the engine, under the middle of the intake. You can turn it around a little whilst the engine is running (and for the sake of your skin, cold) to see that it's top and bottom o-rings are sealed or not).

Intake bellows often crack/perish where you can't see it, the pipe to the fuel pressure regulator or the brake booster and other little vacuum pipes can go in strange places... make sure the engine has a healthy vacuum at 700rpm or so by removing the oil cap and putting your hand over the hole to seal it. It should suck your palm down a bit and run less healthily once the cap is off.

I'd swap the plugs for a set of factory gapped NGK single or at worst, double electrode plugs. The singles are cheaper and fine for M20. If you have removed your plugs, the seals will no longer be sealing very well, causing air to get sucked in, (they compress and are one-time seals). Chk also the rocker cover for sealing joints and anything else obvious.

And it goes without saying, a compression test and a fuel pressure test should be done.

Injectors? Pressure regulator?

that's some helpful information. and sadly, i have no more icv due to the fact that it was damaged so bad. i need to find a new one or working used one before i start working on the car again.

and i can possibly put an air leak to my idle problems since that is common, but i'm really trying to figure out why it doesn't wanna stay on once warm. i'm gonna do a spark plug, and coil change. probably do the cap and rotor at the same time too.
and how would i go about testing the o2 sensor?

[liljos]

lijos I had almost identical symptoms on my now departed 89 but I never solved it. It seemed to me that the electrical system voltage was always low even though the alt and battery were good, I never did find the source of the problem but I always suspected it to be some mysterious short on an unfused circuit (bc pulling fuses never helped), but I could easily be wrong about that. I pestered the hell out of this crowd for answers, they were very helpful but I never solved it. Sorry I can't help but at least you are not alone. Uh... well... now you are I guess tho sorry bro :(

IIRC unsuccessful attempts to fix problem... r/r entire engine system (coil,wires,etc), rewired alt and starter, battery, alt, starter, most of the relays i dunno i got sick of it then I found a huge rusthole that I had never seen before so I scrapped it and bought a california car.

my voltage never seemed low to me, but 'm wondering if a short is causing my sensors to fail. someone said it could be a possible broken wire but i've tested for that and all seemed fine. and did your voltage go back to normal after you replaced all that wiring?

[genphreak]

Dude, the Idle Control Valve is a vital part or all Motronic systems. Are you seriously trying to troubleshoot without functioning properly? Am I reading your posts right?

*** Wihtout an ICV yoru car won't idle at the best of times ***

[liljos]

Dude, the Idle Control Valve is a vital part or all Motronic systems. Are you seriously trying to troubleshoot without functioning properly? Am I reading your posts right?

*** Wihtout an ICV yoru car won't idle at the best of times ***

you're reading the post wrong. i did all my tests with the ICV in the car. after all that i took the ICV out and inspected that. and that was when i realized that it was totally screwed. since then i haven't tried starting the car, i've only looked for vacuum leaks and i found one.


the leak is part # 6 at the top where it connects to the TB
http://static.bmwfans.info/images/epc/MTg3NF9w.png