very rough idle

[pong]

525i
m20
1990

the idle is really really rough...

it jumps from 1000 to 1500 rpm...

when i drive it...

u can really feel the idle jumping...

the speed of the car varies as it jumps... but when im
on the accelerator... maintaining 2000... its normal
except that i feel that there is a lack of power.

any help will be highly appreciated.

thanks!

[632 Regal]

as usual I cant help but have a suggestion. Reboot the computer and get a code after error from the stomp test, rebooting first should zero out on the problem at hand, most other errors fix them selves unless its a vacume related deal.

post results

[shogun]

He cannot make a stomp test, as far as I know pong does not live in USA, so no US spec. car.

[pong]

thanks so much...

i think this is a us spec car (imported frm guam)...

but for some reason i couldn't make the stomp test
to work...

talked to friends who know stuff about engines...
all of us think there is a air intake leak somewhere...

the problem is i couldnt find one...

im fearing that the leak might be from the manifold or
something that drastic...

this afternoon... besides the super rough idle
temp started to climb to the red zone.

then driving it tonight... the temp was jsut a bit above the
middle... pretty much normal...

i dunno if the heat (37 deg C this afternoon) and traffic did contribute
a big part of this... but this is the first time it has happened...
( the overheating and the rough idle)
thanks

[E34-520iSE]

It sounds like a vacuum leak to me too. Even a leaking rocker cover gasket will make the rpm buck. Is there any oil clogging the inlet pipes/ICV/AFM? Try removing all of the intake side of the engine, give it all a good clean up and re-assembling it with new gaskets, seals etc.

HTH,

Shaun M

[pong]

ok... did a part by part diagnosis...

it seems that it is the idle regulating valve

T-SHAPE IDLE REGULATING VALVE BOSCH / 3 POL 1 11/1988 13411433626

i tried removing the plug under it... it was supposed to increase idle speed if i do that... but the thing is... nothing changed... removed the hose going to it... tried to control the air using my hand... idle turned out to be ok.

so this is most probably the culprit.

is there a proper way of testing it?

[shogun]

Pong,
my car does not have an ICV, all is controlled by the EML, so I am not sure how to check. But it looks like it is sticking
http://www.realoem.com/bmw/showparts.do?model=HC23&mospid=47402&btnr=13_0292&hg=13&fg=15&hl=13
Did you clean it already?
Here some comments from Shayne
http://www.bimmerboard.com/forums/posts/247714/
http://www.bimmerboard.com/forums/posts/216810/

[pong]

i think i cleaned it thoroughly already...

soaked it in wd40... a lot of dirt came out...

the flap or whatever ur calling it freely moves...

but the thing is... i think its supposed to be spring
operated... but there is no tension...

it just stays in the position that i push it to...

[Morgenster]

i think i cleaned it thoroughly already...

soaked it in wd40... a lot of dirt came out...

the flap or whatever ur calling it freely moves...

but the thing is... i think its supposed to be spring
operated... but there is no tension...

it just stays in the position that i push it to...

When I cleaned mine that happened too. Don't think it's a problem though. Unless someone disagrees and I turn out to be driving around with a shot ICV ;)

[Ferret]

When I cleaned mine that happened too. Don't think it's a problem though. Unless someone disagrees and I turn out to be driving around with a shot ICV ;)

If I remember correctly, the ICV is an adjust device - IE it has a signal to open more or open less instead of being open x% and closing automatically when there's no signal from the ecu...

[pong]

now...

i determined its not the idle control valve...
tested a friends icv on the car and its working well...

its also not the air flow thing...
did the same thing...

can a clogged catalytic converter be the cause?
any other ideas?

ill be doing a more thorough check of the air intake hoses
again tom

[Ferret]

now...

i determined its not the idle control valve...
tested a friends icv on the car and its working well...

its also not the air flow thing...
did the same thing...

can a clogged catalytic converter be the cause?
any other ideas?

ill be doing a more thorough check of the air intake hoses
again tom

Idle bounce like you've described is almost always certainly a vaccuum leak - caused by a hose with a hairline fracture in it.

It's bouncing because as the icv is opening, more air is being drawn through the crack in a hose (between the MAF and ICV, due to more vaccuum)- causing the icv to close again as there's now too much air. Unplug your MAF with the engine running and see if the idle stabilises - if it does it's a sure sign one of your hoses is cracked.

If so, take all of your air hoses off the vehicle and flex/bend them around a bit - any cracks will immediately show up.

[Morgenster]

I concur. When I had a backfire from the LPG my ICV elbow hose disconnected and I had the same thing albeit in lower RPMs but still fast hunting up and down RPM needle.
If you do the reset and the problem is still there immediately after it's most likely vacuum leak. Sometimes it can be something real stupid once you find it but I'm pretty sure you have it.

[pong]

oh crap...

i looked at the vent hose...
05 VENT HOSE 11151708801
i tried removing it...

it crumbled...

replaced it... still nothing happend...

when its out... idle seems to be better...
but i couldnt run bcoz the idle drops as i change the gear

any ideas where i should look?

[pong]

now... i checked the throttle sensor...

its really oily...

is this probably the cause?

[Ferret]

oh crap...

i looked at the vent hose...
05 VENT HOSE 11151708801
i tried removing it...

it crumbled...

replaced it... still nothing happend...

when its out... idle seems to be better...
but i couldnt run bcoz the idle drops as i change the gear

any ideas where i should look?

If it's done that, it's more than likely half your other hoses are in a similar condition...

[pong]

how can u detect vacuum leaks...

the only thing that i know i can do is to
do it via trial and error...

is there any other way to detect vacuum leaks?

[Gorio]

how can u detect vacuum leaks...

the only thing that i know i can do is to
do it via trial and error...

is there any other way to detect vacuum leaks?


Figured I would throw my two cents in.
You can spray water on all the connections with a squirt bottle. When you hit the right spot things will improve or get worse.
if it is small enough the water will actually seal the air leak for a moment. if it is a bigger leak the water will be drawn in to the engine and cause it to run rougher. This has worked for me in the past.

[pong]

updates... i changed most of the hoses... still no change...

when i unplug the maf...

it stabilizes... but at 4k rpm...

so its still a vacuum leak... d only thing that i didnt change so far
are d hoses from maf to icv to throttle body...

ill look at that again...