HELP: my car gets the hick-ups when it gets bored

[Aussie-E34]

1990 525i auto M20 250,000Kms

This is kind of long but I will try to give you all the symptoms and maybe someone can help me fix this problem. This can happen summer or winter but does seem to follow some kind of pattern. If I want to make it happen I just get in the car first thing in the morning and drive the 5 miles to the freeway and head north. I set the cruise control for 115Kms/hr and drive for about 20 minutes on fairly level road and the engine will start missing and bucking. It feels like there is water in the fuel or bad fuel, but this has been a problem for about 2 years so it can't be bad fuel. If, when I feel the first missing, I disengage the cruise control an start driving using the gas pedel and accelerate and decelerate conciously up and down, the problem will go away and the car will drive fine for the rest of the day. If I leave the cruise control on, the car will start bucking more and becomes harded to settle down. If I take the same trip first thing in the morning and don't use the cruise control and drive using the gas pedel and gently accelerate and and decelerate, the problem will not happen. Once this problem has happened once, I can drive the rest of the day and it will never happen again that day. Even without the cruise control, if I drive for a while at the same speed with even preasure on the gas pedel, the car can start missing and bucking but usually flooring it and reving the engine will settle it down.
Sorry about the length of this but I can't figure out what is happening. Can anyony help?

[wingman]

I used to have a vacuum leak and fixing that made the motor run more smoothly. Even with this fixed on the very very odd occaission I will feel a miss when using cruise. It's almost like one cylinder doesn't fire but it's only very slight and as I say very very occaissional. Where are you by the way?

[Aussie-E34]

Central Coast New South Wales just north of Sydney

[Ross]

Anyone think this could be related to the purging of the vapor canister?

[ThoreauHD]

Sounds like a vacuum leak like he fella above said. I had the same symptoms.

Pressure pushing down on me
Pressing down on you no man ask for
Under pressure - that burns a building
down
Splits a family in two
Puts people on streets
It's the terror of knowing
What this world is about
Watching some good friends
Screaming let me out
Pray tomorrow - gets me higher
Pressure on people - people on streets

[HDhandyman]

Sounds like a vacuum leak like he fella above said. I had the same symptoms.

Pressure pushing down on me
Pressing down on you no man ask for
Under pressure - that burns a building
down
Splits a family in two
Puts people on streets
It's the terror of knowing
What this world is about
Watching some good friends
Screaming let me out
Pray tomorrow - gets me higher
Pressure on people - people on streets

De De Deh
di da di deh do

doom, doom, doom -- doom do do doom / doom, doom, doom, -- doom do do doom Ha PRESSURE!

"To the extreme I rock a mic like a vandal
Light up a stage and wax a chump like a candle."


Hijack;)

[ThoreauHD]

Oh Nooos!

It's a bird.. It's a plane.. IT'S...

http://i4.photobucket.com/albums/y106/toasty0z/vanilla_icetronaut.jpg

[Aussie-E34]

Anyone think this could be related to the purging of the vapor canister?
Vapor canister? I wasn't aware there was such a thing but it makes sense to me. I was thinking that it must be some kind of moisture that builds up when the car is sitting overnight and after it works its way through the system and causes my wife to threaten to sell my E34, it is gone for the day and doesn't pop up again until the next day. Where is this vapor canister and is it something I can service myself?

[rob101]

vapour canister aka charcoal canister, a canister filled with activated characoal to filter petrol fumes.
you might want to fill out your profile
it gives most people the shits when they can't tell what model you drive in your posts

[Aussie-E34]

Sorry about the profile thing. I just signed up and wasn't sure what to do. I think I fixed it.

[Paul in NZ]

make sure your plug leads,dis cap and rotor are aok and clean and no cracks...

[Aussie-E34]

They were all replaced about 4 months ago

[Aussie-E34]

Thanks Rob. I can't find anything about nthe charcoal canister in the Bentley. Can anyone tell me where it is on the 1990 525 M20 and if I can clean it or service it or replace it myself. Thanks

[genphreak]

They were all replaced about 4 months agoCharcoal canister sounds like a good bet. But if there is a leak it might be leaning out. How do the plugs look? If unsure post some pics other members will tell you. Check also the purge valve that the ECU opens and closes to draw the deadly gases from the canister- you can take it off, check it works and seals by blowing through it and applying 12V.

Canisters are never replaced in Aus as we don't believe in low emissions or caring for cars. I don't think BMW even change them.

They cost maybe $150 here or about $40 from the US- www.bmaparts.com (http://www.bmaparts.com). When was your O2 sensor done? I'd change that too- they only last 100,000km or so- if the engine ever had the head done maybe it might need a new one anyway.

:) Nick

[Aussie-E34]

Thanks everyone for your advice and guidence. I will try the charcoal canister as soon as I can locate one, and ask me mechanic if he can find any vacuum leaks. I'll let you know the outcome.

[wingman]

This is my post about the vacuum leak. If you read down the thread I fixed the leak with a small screw. I posted some pics of where my problem was. Good Luck!
http://www.bimmer.info/forum/showthread.php?t=20681

[Tim from OZ]

This is my post about the vacuum leak. If you read down the thread I fixed the leak with a small screw. I posted some pics of where my problem was. Good Luck!
http://www.bimmer.info/forum/showthread.php?t=20681
Thanks Wingman but mine seems to have the little black rubber cap sealing it there. When you had the vacuum leak did it affect drivability or was irt just rough idle?

[SilverFive90]

5/90 525i (M20)
I hear a lot of people talking about the head...and getting it done?
What exactly does that entail....my car has 200k....should this be something I should be considering getting done?

[gmannino]

Also check your spark plug wires to ensure that they are in good condition, If they havnt been replaced you might wanna swap them with new ones.

An even easier fix, fuel injectors get clogged after 16 years, add come STP or Chevron fuel injector cleaner and check to see if you are still getting bucking. If it goes away for a while, you need to buy new ones or send them out to get cleaned.